sahilTakiar commented on a change in pull request #595: HDFS-14304: High lock contention on hdfsHashMutex in libhdfs URL: https://github.com/apache/hadoop/pull/595#discussion_r267898778
########## File path: hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/jclasses.c ########## @@ -0,0 +1,135 @@ +/** + * 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. + */ + +#include "exception.h" +#include "jclasses.h" +#include "jni_helper.h" +#include "os/mutexes.h" + +#include <assert.h> + +/** + * Whether initCachedClasses has been called or not. Protected by the mutex + * jclassInitMutex. + */ +static int jclassesInitialized = 0; + +struct javaClassAndName { + jclass javaClass; + const char *className; +}; + +/** + * A collection of commonly used jclass objects that are used throughout + * libhdfs. The jclasses are loaded immediately after the JVM is created (see + * initCachedClasses). The array is indexed using CachedJavaClass. + */ +struct javaClassAndName cachedJavaClasses[NUM_CACHED_CLASSES]; + +/** + * Helper method that creates and sets a jclass object given a class name. + * Returns a jthrowable on error, NULL otherwise. + */ +static jthrowable initCachedClass(JNIEnv *env, const char *className, + jclass *cachedJclass) { + assert(className != NULL && "Found a CachedJavaClass without a class " + "name"); + jthrowable jthr = NULL; + jclass tempLocalClassRef; + tempLocalClassRef = (*env)->FindClass(env, className); + if (!tempLocalClassRef) { + jthr = getPendingExceptionAndClear(env); + goto done; + } + *cachedJclass = (jclass) (*env)->NewGlobalRef(env, tempLocalClassRef); + if (!*cachedJclass) { + jthr = getPendingExceptionAndClear(env); + goto done; + } +done: + destroyLocalReference(env, tempLocalClassRef); + return jthr; +} + +jthrowable initCachedClasses(JNIEnv* env) { + mutexLock(&jclassInitMutex); + if (!jclassesInitialized) { + // Set all the class names + cachedJavaClasses[JC_CONFIGURATION].className = + "org/apache/hadoop/conf/Configuration"; + cachedJavaClasses[JC_PATH].className = + "org/apache/hadoop/fs/Path"; + cachedJavaClasses[JC_FILE_SYSTEM].className = + "org/apache/hadoop/fs/FileSystem"; + cachedJavaClasses[JC_FS_STATUS].className = + "org/apache/hadoop/fs/FsStatus"; + cachedJavaClasses[JC_FILE_UTIL].className = + "org/apache/hadoop/fs/FileUtil"; + cachedJavaClasses[JC_BLOCK_LOCATION].className = + "org/apache/hadoop/fs/BlockLocation"; + cachedJavaClasses[JC_DFS_HEDGED_READ_METRICS].className = + "org/apache/hadoop/hdfs/DFSHedgedReadMetrics"; + cachedJavaClasses[JC_DISTRIBUTED_FILE_SYSTEM].className = + "org/apache/hadoop/hdfs/DistributedFileSystem"; + cachedJavaClasses[JC_FS_DATA_INPUT_STREAM].className = + "org/apache/hadoop/fs/FSDataInputStream"; + cachedJavaClasses[JC_FS_DATA_OUTPUT_STREAM].className = + "org/apache/hadoop/fs/FSDataOutputStream"; + cachedJavaClasses[JC_FILE_STATUS].className = + "org/apache/hadoop/fs/FileStatus"; + cachedJavaClasses[JC_FS_PERMISSION].className = + "org/apache/hadoop/fs/permission/FsPermission"; + cachedJavaClasses[JC_READ_STATISTICS].className = + "org/apache/hadoop/hdfs/ReadStatistics"; + cachedJavaClasses[JC_HDFS_DATA_INPUT_STREAM].className = + "org/apache/hadoop/hdfs/client/HdfsDataInputStream"; + cachedJavaClasses[JC_DOMAIN_SOCKET].className = + "org/apache/hadoop/net/unix/DomainSocket"; + cachedJavaClasses[JC_URI].className = + "java/net/URI"; + cachedJavaClasses[JC_BYTE_BUFFER].className = + "java/nio/ByteBuffer"; + cachedJavaClasses[JC_ENUM_SET].className = + "java/util/EnumSet"; + cachedJavaClasses[JC_EXCEPTION_UTILS].className = + "org/apache/commons/lang3/exception/ExceptionUtils"; + + // Create and set the jclass objects based on the class names set above + jthrowable jthr; + int numCachedClasses = + sizeof(cachedJavaClasses) / sizeof(struct javaClassAndName); + for (int i = 0; i < numCachedClasses; i++) { + jthr = initCachedClass(env, cachedJavaClasses[i].className, + &cachedJavaClasses[i].javaClass); + if (jthr) { + return jthr; Review comment: Fixed ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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