jt2594838 commented on a change in pull request #2488:
URL: https://github.com/apache/iotdb/pull/2488#discussion_r557821833
##########
File path:
server/src/main/java/org/apache/iotdb/db/engine/storagegroup/StorageGroupProcessor.java
##########
@@ -261,6 +268,79 @@ public void setReady(boolean ready) {
private List<CloseFileListener> customCloseFileListeners =
Collections.emptyList();
private List<FlushListener> customFlushListeners = Collections.emptyList();
+ private static final int WAL_BUFFER_SIZE =
+ IoTDBDescriptor.getInstance().getConfig().getWalBufferSize() / 2;
+
+ private static final int MAX_WAL_BYTEBUFFER_NUM =
+
IoTDBDescriptor.getInstance().getConfig().getConcurrentWritingTimePartition() *
4;
+
+ private static final long DEFAULT_POOL_TRIM_INTERVAL_MILLIS = 10_000;
+
+ private final Deque<ByteBuffer> walByteBufferPool = new LinkedList<>();
+
+ private int currentWalPoolSize = 0;
Review comment:
This field is used in a waiting condition, so maybe it is better made
volatile?
##########
File path:
server/src/main/java/org/apache/iotdb/db/writelog/node/ExclusiveWriteLogNode.java
##########
@@ -92,6 +90,11 @@ public ExclusiveWriteLogNode(String identifier) {
}
}
+ public void initBuffer(ByteBuffer[] byteBuffers) {
+ this.logBufferWorking = byteBuffers[0];
+ this.logBufferIdle = byteBuffers[1];
+ }
Review comment:
Maybe you can keep `byteBuffers` as a field, so `delete()` can be
simpler.
##########
File path:
server/src/main/java/org/apache/iotdb/db/engine/storagegroup/StorageGroupProcessor.java
##########
@@ -261,6 +268,79 @@ public void setReady(boolean ready) {
private List<CloseFileListener> customCloseFileListeners =
Collections.emptyList();
private List<FlushListener> customFlushListeners = Collections.emptyList();
+ private static final int WAL_BUFFER_SIZE =
+ IoTDBDescriptor.getInstance().getConfig().getWalBufferSize() / 2;
+
+ private static final int MAX_WAL_BYTEBUFFER_NUM =
+
IoTDBDescriptor.getInstance().getConfig().getConcurrentWritingTimePartition() *
4;
+
+ private static final long DEFAULT_POOL_TRIM_INTERVAL_MILLIS = 10_000;
+
+ private final Deque<ByteBuffer> walByteBufferPool = new LinkedList<>();
+
+ private int currentWalPoolSize = 0;
+
+
+ /**
+ * get the direct byte buffer from pool, each fetch contains two ByteBuffer
+ */
+ public ByteBuffer[] getWalDirectByteBuffer() {
+ ByteBuffer[] res = new ByteBuffer[2];
+ synchronized (walByteBufferPool) {
+ while (walByteBufferPool.isEmpty() && currentWalPoolSize + 2 >
MAX_WAL_BYTEBUFFER_NUM) {
+ try {
+ walByteBufferPool.wait();
+ } catch (InterruptedException e) {
+ Thread.currentThread().interrupt();
+ logger
+ .error("getDirectByteBuffer occurs error while waiting for
DirectByteBuffer"
+ + "group {}", storageGroupName, e);
+ }
+ }
+ // If the queue is not empty, it must have at least two.
+ if (!walByteBufferPool.isEmpty()) {
+ res[0] = walByteBufferPool.pollFirst();
+ res[1] = walByteBufferPool.pollFirst();
+ } else {
+ // if the queue is empty and current size is less than
MAX_BYTEBUFFER_NUM
+ // we can construct another two more new byte buffer
+ currentWalPoolSize += 2;
+ res[0] = ByteBuffer.allocateDirect(WAL_BUFFER_SIZE);
+ res[1] = ByteBuffer.allocateDirect(WAL_BUFFER_SIZE);
+ }
+ }
+ return res;
+ }
+
+ /**
+ * put the byteBuffer back to pool
+ */
+ public void releaseWalBuffer(ByteBuffer[] byteBuffers) {
+ for (ByteBuffer byteBuffer : byteBuffers) {
+ byteBuffer.clear();
+ }
+ synchronized (walByteBufferPool) {
+ walByteBufferPool.addLast(byteBuffers[0]);
+ walByteBufferPool.addLast(byteBuffers[1]);
+ walByteBufferPool.notifyAll();
+ }
+ }
+
+ /**
+ * trim the size of the pool and release the memory of needless direct byte
buffer
+ */
+ private void trimTask() {
+ synchronized (walByteBufferPool) {
+ int expectedSize =
+ (workSequenceTsFileProcessors.size() +
workUnsequenceTsFileProcessors.size()) * 2;
+ while (expectedSize < currentWalPoolSize &&
!walByteBufferPool.isEmpty()) {
+ MmapUtil.clean((MappedByteBuffer) walByteBufferPool.removeLast());
+ MmapUtil.clean((MappedByteBuffer) walByteBufferPool.removeLast());
+ currentWalPoolSize -= 2;
+ }
+ }
+ }
Review comment:
The strategy may introduce thrashing when a TsFile is closed and
`workSequenceTsFileProcessors.size()` is reduced for one instant, while another
file just returned its buffers. If `trimTask()` is triggered at the moment, 2
buffers that could have been used by the next file are cleaned.
One possible improvement is to record the timestamp when the pool becomes
non-empty, unset it when the pool becomes empty, and only trim a pool if it has
been non-empty for a relatively long time, so the just-returned buffers will
not be purged.
##########
File path: server/src/main/java/org/apache/iotdb/db/utils/MmapUtil.java
##########
@@ -0,0 +1,31 @@
+/*
+ * 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.iotdb.db.utils;
+
+import io.netty.util.internal.PlatformDependent;
+import java.nio.MappedByteBuffer;
+
+public class MmapUtil {
+
+ public static void clean(MappedByteBuffer mappedByteBuffer) {
+ if (mappedByteBuffer == null || !mappedByteBuffer.isDirect() ||
mappedByteBuffer.capacity()== 0)
+ return;
Review comment:
Mind the code style that `{}` should be used.
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