[GitHub] [ignite-3] sashapolo commented on a change in pull request #566: IGNITE-15817 Basic PageIO abstractions ported from Ignite 2.x

[GitBox]

sashapolo commented on a change in pull request #566:
URL: https://github.com/apache/ignite-3/pull/566#discussion_r788811202



##########
File path: 
modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -261,6 +262,26 @@ private static void addByteAsHex(StringBuilder sb, byte b) 
{
         sb.append(Integer.toHexString(MASK & b >>> 
4)).append(Integer.toHexString(MASK & b));
     }
 
+    /**
+     * Returns a hex string representation of the given long value.
+     *
+     * @param val Value to convert to string.
+     * @return Hex string.
+     */
+    public static String hexLong(long val) {
+        return new IgniteStringBuilder(16).appendHex(val).toString();
+    }
+
+    /**
+     * Rtturns a hex string representation of the given integer value.

Review comment:
       ```suggestion
        * Returns a hex string representation of the given integer value.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>

Review comment:
       ```suggestion
    * <h3>Page ID rotation</h3>
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.

Review comment:
       ```suggestion
    * flags (8 bits). Higher 8 bits of page ID are unused and reserved to 
address entries inside data pages or page ID rotation.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented
+ * each time a page is reused (page ID rotation). This ID should be verified 
after page read and a page
+ * should be discarded if full ID is different.
+ *
+ * <p>Effective page ID is page ID with zeroed bits used for page ID rotation.
+ */
+public class FullPageId {
+    /** Null page ID. */

Review comment:
       What is a "Null page"?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageIdAllocator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Allocates page ID's.
+ */
+public interface PageIdAllocator {
+    /**
+     * Flag for a Data page. Also used by partition meta and tracking pages. 
This type doesn't use the Page ID rotation mechanism.
+     */
+    public static final byte FLAG_DATA = 1;
+
+    /**
+     * Flag for an internal structure page. This type uses the Page ID 
rotation mechanism.
+     */
+    public static final byte FLAG_AUX = 2;
+
+    /**
+     * Max partition ID that can be used by affinity.
+     */
+    public static final int MAX_PARTITION_ID = 65500;
+
+    /**
+     * Special partition reserved for index space.
+     */
+    public static final int INDEX_PARTITION = 0xFFFF;
+
+    /**
+     * Allocates a page from the space for the given partition ID and the 
given flags.
+     *
+     * @param groupId Group ID.
+     * @param partId  Partition ID.
+     * @return Allocated page ID.
+     */
+    public long allocatePage(int groupId, int partId, byte flags) throws 
IgniteInternalCheckedException;
+
+    /**
+     * The given page is free now.

Review comment:
       ```suggestion
        * Frees (deallocates?) the given page.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.

Review comment:
       ```suggestion
        * Returns a page's size in bytes.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.
+     *
+     * @param groupId Group id.
+     */
+    int realPageSize(int groupId);
+
+    /**
+     * Returns a page size with system overhead, in bytes.
+     */
+    int systemPageSize();
+
+    /**
+     * Wraps a page address into a direct byte buffer.
+     *
+     * @param pageAddr Page address.
+     * @return Page byte buffer.
+     */
+    ByteBuffer pageBuffer(long pageAddr);

Review comment:
       what is a page address? Is it an index or is it an ID or is it something 
else? We should add a reference to the method that returns these addresses

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.

Review comment:
       ```suggestion
        * {@link #releasePage(int, long, long)}. This method will allocate a 
page with the given ID if it doesn't exist.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling

Review comment:
       ```suggestion
        * Returns an absolute pointer to a page, associated with the given page 
ID. Each page obtained with this method must be released by calling
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and

Review comment:
       ```suggestion
    * <p>Generally, a full page ID consists of a group ID and a page ID. A page 
ID consists of a page index (32 bits), a partition ID (16 bits) and
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented
+ * each time a page is reused (page ID rotation). This ID should be verified 
after page read and a page

Review comment:
       ```suggestion
    * each time a page is reused. This value should be verified after every 
page read and the page
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented
+ * each time a page is reused (page ID rotation). This ID should be verified 
after page read and a page
+ * should be discarded if full ID is different.

Review comment:
       ```suggestion
    * should be discarded if the full ID is different.
   ```

##########
File path: 
modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java
##########
@@ -261,6 +262,26 @@ private static void addByteAsHex(StringBuilder sb, byte b) 
{
         sb.append(Integer.toHexString(MASK & b >>> 
4)).append(Integer.toHexString(MASK & b));
     }
 
+    /**
+     * Returns a hex string representation of the given long value.
+     *
+     * @param val Value to convert to string.
+     * @return Hex string.
+     */
+    public static String hexLong(long val) {

Review comment:
       I would suggest extracting this and similar method to something like 
`IgniteStringUtils`, otherwise this class is getting too bloated

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.

Review comment:
       ```suggestion
    * flags. Higher 8 bits of a page ID are unused and reserved for addressing 
entries inside data pages or for page ID rotation.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.

Review comment:
       Maybe it would be a good idea to rename this method...

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented
+ * each time a page is reused (page ID rotation). This ID should be verified 
after page read and a page
+ * should be discarded if full ID is different.
+ *
+ * <p>Effective page ID is page ID with zeroed bits used for page ID rotation.

Review comment:
       ```suggestion
    * <p>Effective page ID is a page ID with zeroed bits used for page ID 
rotation.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page or {@code 0} if page has been 
reused.
+     */
+    public long readLock(int groupId, long pageId, long page);
+
+    /**
+     * Obtains read lock without checking page tag.

Review comment:
       And what is a page tag?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented

Review comment:
       ```suggestion
    * This is ensured by page ID rotation - together with the ID of page B we 
write a value that is incremented
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and

Review comment:
       What is a "group ID"?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageIdAllocator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Allocates page ID's.
+ */
+public interface PageIdAllocator {
+    /**
+     * Flag for a Data page. Also used by partition meta and tracking pages. 
This type doesn't use the Page ID rotation mechanism.
+     */
+    public static final byte FLAG_DATA = 1;
+
+    /**
+     * Flag for an internal structure page. This type uses the Page ID 
rotation mechanism.
+     */
+    public static final byte FLAG_AUX = 2;
+
+    /**
+     * Max partition ID that can be used by affinity.
+     */
+    public static final int MAX_PARTITION_ID = 65500;
+
+    /**
+     * Special partition reserved for index space.

Review comment:
       ```suggestion
        * Special partition reserved for the index space.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageIdAllocator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Allocates page ID's.

Review comment:
       ```suggestion
    * Class responsible for allocating new page IDs.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |
+ * +---------+-----------+------------+--------------------------+
+ * </pre>
+ *
+ * <p><h3>Page ID rotation</h3>
+ * There are scenarios when we reference one page (B) from within another page 
(A) by page ID. It is also
+ * possible that this first page (B) is concurrently reused for a different 
purpose. In this
+ * case we should have a mechanism to determine that the reference from page 
(A) to page (B) is no longer valid.
+ * This is ensured by page ID rotation - together with page's (B) ID we should 
write some value that is incremented
+ * each time a page is reused (page ID rotation). This ID should be verified 
after page read and a page
+ * should be discarded if full ID is different.
+ *
+ * <p>Effective page ID is page ID with zeroed bits used for page ID rotation.
+ */
+public class FullPageId {
+    /** Null page ID. */
+    public static final FullPageId NULL_PAGE = new FullPageId(-1, -1);
+
+    /** Page ID. */
+    private final long pageId;
+
+    /** Effective page ID. */
+    private final long effectivePageId;
+
+    /** Group ID. */
+    private final int groupId;
+
+    /**
+     * Constructor.
+     *
+     * @param pageId  Page ID.
+     * @param groupId Group ID.
+     */
+    public FullPageId(long pageId, int groupId) {
+        this.pageId = pageId;
+        this.groupId = groupId;
+
+        effectivePageId = PageIdUtils.effectivePageId(pageId);
+    }
+
+    /**
+     * Returns a page ID.
+     */
+    public long pageId() {
+        return pageId;
+    }
+
+    /**
+     * Returns an effective page ID.
+     */
+    public long effectivePageId() {
+        return effectivePageId;
+    }
+
+    /**
+     * Returns a group ID.
+     */
+    public int groupId() {
+        return groupId;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+
+        if (!(o instanceof FullPageId)) {
+            return false;
+        }
+
+        FullPageId that = (FullPageId) o;
+
+        return effectivePageId == that.effectivePageId && groupId == 
that.groupId;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public int hashCode() {
+        return hashCode0(groupId, effectivePageId);
+    }
+
+    /**
+     * Returns hash code of the ID.

Review comment:
       What's the difference between this method and `hashCode()`?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and
+ * flags. Higher 8 bits of page ID are unused and reserved to address entries 
inside data pages or page ID rotation.
+ *
+ * <p>Partition ID {@code 0xFFFF} is reserved for index pages.
+ *
+ * <p>The structure of a page ID is shown in the diagram below:
+ * <pre>
+ * +---------+-----------+------------+--------------------------+
+ * | 8 bits  |   8 bits  |  16 bits   |         32 bits          |
+ * +---------+-----------+------------+--------------------------+
+ * |  OFFSET |   FLAGS   |PARTITION ID|       PAGE INDEX         |

Review comment:
       Should we change `OFFSET` to `RESERVED`?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageIdAllocator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Allocates page ID's.
+ */
+public interface PageIdAllocator {
+    /**
+     * Flag for a Data page. Also used by partition meta and tracking pages. 
This type doesn't use the Page ID rotation mechanism.
+     */
+    public static final byte FLAG_DATA = 1;
+
+    /**
+     * Flag for an internal structure page. This type uses the Page ID 
rotation mechanism.
+     */
+    public static final byte FLAG_AUX = 2;
+
+    /**
+     * Max partition ID that can be used by affinity.

Review comment:
       This sentence makes little sense to me, can we improve it?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageIdAllocator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Allocates page ID's.
+ */
+public interface PageIdAllocator {
+    /**
+     * Flag for a Data page. Also used by partition meta and tracking pages. 
This type doesn't use the Page ID rotation mechanism.
+     */
+    public static final byte FLAG_DATA = 1;
+
+    /**
+     * Flag for an internal structure page. This type uses the Page ID 
rotation mechanism.
+     */
+    public static final byte FLAG_AUX = 2;
+
+    /**
+     * Max partition ID that can be used by affinity.
+     */
+    public static final int MAX_PARTITION_ID = 65500;
+
+    /**
+     * Special partition reserved for index space.
+     */
+    public static final int INDEX_PARTITION = 0xFFFF;
+
+    /**
+     * Allocates a page from the space for the given partition ID and the 
given flags.
+     *
+     * @param groupId Group ID.
+     * @param partId  Partition ID.
+     * @return Allocated page ID.
+     */
+    public long allocatePage(int groupId, int partId, byte flags) throws 
IgniteInternalCheckedException;

Review comment:
       Should we accept a `FullPageId` here and in other methods?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/FullPageId.java
##########
@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.util.PageIdUtils;
+import org.apache.ignite.internal.util.IgniteUtils;
+import org.apache.ignite.lang.IgniteStringBuilder;
+
+/**
+ * Compound object used to address a page in the global page space.
+ * <h3>Page ID structure</h3>
+ *
+ * <p>Generally, a full page ID consists of a group ID and page ID. A page ID 
consists of page index (32 bits), partition ID (16 bits) and

Review comment:
       What is a "page index"?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.

Review comment:
       I'm sorry, but this is not a good javadoc

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.
+     *
+     * @param groupId Group id.
+     */
+    int realPageSize(int groupId);
+
+    /**
+     * Returns a page size with system overhead, in bytes.
+     */
+    int systemPageSize();

Review comment:
       Same here, I think this method should be renamed, because otherwise it 
creates an impression that it returns the size of a "system page"

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.
+     *
+     * @param groupId Group id.
+     */
+    int realPageSize(int groupId);
+
+    /**
+     * Returns a page size with system overhead, in bytes.

Review comment:
       ```suggestion
        * Returns a page's size with system overhead, in bytes.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.

Review comment:
       ```suggestion
        * Returns a page size without the encryption overhead.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.
+     *
+     * @param groupId Group id.
+     */
+    int realPageSize(int groupId);
+
+    /**
+     * Returns a page size with system overhead, in bytes.
+     */
+    int systemPageSize();
+
+    /**
+     * Wraps a page address into a direct byte buffer.
+     *
+     * @param pageAddr Page address.
+     * @return Page byte buffer.
+     */
+    ByteBuffer pageBuffer(long pageAddr);
+
+    /**
+     * Returns a total number of loaded pages in memory.

Review comment:
       ```suggestion
        * Returns the total number of pages loaded into memory.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling

Review comment:
       ```suggestion
        * Returns an absolute pointer to a page, associated with the given page 
ID. Each pointer obtained with this method must be released by calling
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.

Review comment:
       I'm sorry, but this is also not a good javadoc

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.

Review comment:
       ```suggestion
        * {@link #releasePage(int, long, long)}. This method will allocate a 
page with the given ID if it doesn't exist.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageMemory.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import java.nio.ByteBuffer;
+import org.apache.ignite.internal.pagememory.io.PageIo;
+import org.apache.ignite.internal.pagememory.io.PageIoRegistry;
+
+/**
+ * Page memory.
+ */
+public interface PageMemory extends PageIdAllocator, PageSupport {
+    /**
+     * Returns a page size in bytes.
+     */
+    int pageSize();
+
+    /**
+     * Returns a page size without encryption overhead.
+     *
+     * @param groupId Group id.
+     */
+    int realPageSize(int groupId);
+
+    /**
+     * Returns a page size with system overhead, in bytes.
+     */
+    int systemPageSize();
+
+    /**
+     * Wraps a page address into a direct byte buffer.
+     *
+     * @param pageAddr Page address.
+     * @return Page byte buffer.
+     */
+    ByteBuffer pageBuffer(long pageAddr);
+
+    /**
+     * Returns a total number of loaded pages in memory.
+     */
+    long loadedPages();
+
+    /**
+     * Returns a registry to retrieve {@link PageIo} instances for pages.

Review comment:
       ```suggestion
        * Returns a registry to obtain {@link PageIo} instances for pages.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.

Review comment:
       ```suggestion
        * Acquires a read lock associated with the given page.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.

Review comment:
       ```suggestion
        * Releases pages acquired by any of the {@code acquirePage} methods.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);

Review comment:
       I guess the last parameter should be changed to `pageAddr`. Also, why 
don't we accept a `FullPageId` here as well?

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page or {@code 0} if page has been 
reused.
+     */
+    public long readLock(int groupId, long pageId, long page);
+
+    /**
+     * Obtains read lock without checking page tag.

Review comment:
       ```suggestion
        * Acquires a read lock, associated with a given page, without checking 
the page tag.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page or {@code 0} if page has been 
reused.
+     */
+    public long readLock(int groupId, long pageId, long page);
+
+    /**
+     * Obtains read lock without checking page tag.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page.
+     */
+    public long readLockForce(int groupId, long pageId, long page);
+
+    /**
+     * Releases locked page.

Review comment:
       ```suggestion
        * Releases a read lock, associated with a given page.
   ```

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page or {@code 0} if page has been 
reused.
+     */
+    public long readLock(int groupId, long pageId, long page);
+
+    /**
+     * Obtains read lock without checking page tag.

Review comment:
       Why does this method accepts a `long page` parameter and then returns 
another `long`? What is the difference? `Pointer for reading the page` doesn't 
help with understanding this.

##########
File path: 
modules/page-memory/src/main/java/org/apache/ignite/internal/pagememory/PageSupport.java
##########
@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.ignite.internal.pagememory;
+
+import org.apache.ignite.internal.pagememory.metric.IoStatisticsHolder;
+import org.apache.ignite.lang.IgniteInternalCheckedException;
+
+/**
+ * Supports operations on pages.
+ */
+public interface PageSupport {
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId) throws 
IgniteInternalCheckedException;
+
+    /**
+     * Returns the page absolute pointer associated with the given page ID. 
Each page obtained with this method must be released by calling
+     * {@link #releasePage(int, long, long)}. This method will allocate page 
with given ID if it doesn't exist.
+     *
+     * @param groupId    Group ID.
+     * @param pageId     Page ID.
+     * @param statHolder Statistics holder to track IO operations.
+     * @return Page pointer.
+     * @throws IgniteInternalCheckedException If failed.
+     */
+    public long acquirePage(int groupId, long pageId, IoStatisticsHolder 
statHolder) throws IgniteInternalCheckedException;
+
+    /**
+     * Releases page acquired by one of {@code acquirePage} methods.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID to release.
+     * @param page    Page pointer returned by the corresponding {@code 
acquirePage} call.
+     */
+    public void releasePage(int groupId, long pageId, long page);
+
+    /**
+     * Acquires a read lock on the page.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page or {@code 0} if page has been 
reused.
+     */
+    public long readLock(int groupId, long pageId, long page);
+
+    /**
+     * Obtains read lock without checking page tag.
+     *
+     * @param groupId Group ID.
+     * @param pageId  Page ID.
+     * @param page    Page pointer.
+     * @return Pointer for reading the page.
+     */
+    public long readLockForce(int groupId, long pageId, long page);
+
+    /**
+     * Releases locked page.

Review comment:
       What will happen if I will try to release a page that had not been 
locked?




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