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https://issues.apache.org/jira/browse/HDFS-17496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17913639#comment-17913639
]
ASF GitHub Bot commented on HDFS-17496:
---------------------------------------
kokon191 commented on code in PR #7280:
URL: https://github.com/apache/hadoop/pull/7280#discussion_r1918141263
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java:
##########
@@ -112,6 +116,21 @@ public static boolean dirNoFilesRecursive(
return true;
}
+ /**
+ * Take an example.
+ * We hava a block with blockid mapping to:
+ *
"/data1/hadoop/hdfs/datanode/current/BP-xxxx/current/finalized/subdir0/subdir0"
+ * We return "subdir0/subdir0".
Review Comment:
Can use `subdir0/subdir1` as the example to make it more generic than
`subdir0/subdir0`
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DatanodeUtil.java:
##########
@@ -120,13 +139,21 @@ public static boolean dirNoFilesRecursive(
* @return
*/
public static File idToBlockDir(File root, long blockId) {
- int d1 = (int) ((blockId >> 16) & 0x1F);
- int d2 = (int) ((blockId >> 8) & 0x1F);
- String path = DataStorage.BLOCK_SUBDIR_PREFIX + d1 + SEP +
- DataStorage.BLOCK_SUBDIR_PREFIX + d2;
+ String path = idToBlockDirSuffix(blockId);
return new File(root, path);
}
+ public static List<String> getAllSubDirNameForDataSetLock() {
Review Comment:
`Name` -> `Names`
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataSetSubLockStrategy.java:
##########
@@ -0,0 +1,36 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.hdfs.server.datanode;
+
+import java.util.List;
+
+/**
+ * This interface is used to generate sub lock name for a blockid.
+ */
+public interface DataSetSubLockStrategy {
+
+ /**
+ * Generate sub lock name for the given blockid.
+ * @param blockid the block id.
+ * @return sub lock name for the input blockid.
+ */
+ String blockIdToSubLock(long blockid);
+
+ List<String> getAllSubLockName();
Review Comment:
`Name` -> `Names`
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/DataNodeLockManager.java:
##########
@@ -29,7 +29,8 @@ public interface DataNodeLockManager<T extends
AutoCloseDataSetLock> {
*/
Review Comment:
Update this javadoc to have description for 3 levels of locks. I think there
might be other spots in code comments/javadocs where 2 levels of locks are
used, might need to comb through the code to find them.
> DataNode supports more fine-grained dataset lock based on blockid
> -----------------------------------------------------------------
>
> Key: HDFS-17496
> URL: https://issues.apache.org/jira/browse/HDFS-17496
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Reporter: farmmamba
> Assignee: farmmamba
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.5.0
>
> Attachments: image-2024-04-23-16-17-07-057.png
>
>
> Recently, we used NvmeSSD as volumes in datanodes and performed some stress
> tests.
> We found that NvmeSSD and HDD disks achieve similar performance when create
> lots of small files, such as 10KB.
> This phenomenon is counterintuitive. After analyzing the metric monitoring ,
> we found that fsdataset lock became the bottleneck in high concurrency
> scenario.
>
> Currently, we have two level locks which are BLOCK_POOL and VOLUME. We can
> further split the volume lock to DIR lock.
> DIR lock is defined as below： given a blockid, we can determine which subdir
> this block will be placed in finalized dir. We just use
> subdir[0-31]/subdir[0-31] as the
> name of DIR lock.
> More details, please refer to method DatanodeUtil#idToBlockDir：
> {code:java}
> public static File idToBlockDir(File root, long blockId) {
> int d1 = (int) ((blockId >> 16) & 0x1F);
> int d2 = (int) ((blockId >> 8) & 0x1F);
> String path = DataStorage.BLOCK_SUBDIR_PREFIX + d1 + SEP +
> DataStorage.BLOCK_SUBDIR_PREFIX + d2;
> return new File(root, path);
> } {code}
> The performance comparison is as below:
> experimental setup:
> 3 DataNodes with single disk.
> 10 Cients concurrent write and delete files after writing.
> 550 threads per Client.
> !image-2024-04-23-16-17-07-057.png!
>
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