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https://issues.apache.org/jira/browse/HDFS-13821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17424511#comment-17424511
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Janus Chow commented on HDFS-13821:
-----------------------------------

A comparison of the LocalCacheTest result on local PC would be as follows:
||Argument||original stats (ms)||set initialCapacity (ms)||
|10000 8 1000|0.059|0.042|
|10000 16 1000|0.131|0.076|
|10000 32 1000|0.268|0.1|
|10000 64 1000|0.453|0.129|
|10000 128 1000|0.871|0.175|
|10000 256 1000|1.796|0.258|
|10000 512 1000|3.322|0.457|
|10000 1024 1000|7.107|0.796|
|10000 1024 10000|7.6741|0.5801|

 

> RBF: Add dfs.federation.router.mount-table.cache.enable so that users can 
> disable cache
> ---------------------------------------------------------------------------------------
>
>                 Key: HDFS-13821
>                 URL: https://issues.apache.org/jira/browse/HDFS-13821
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs
>    Affects Versions: 3.1.0, 2.9.1, 3.0.3
>            Reporter: Hui Fei
>            Assignee: Hui Fei
>            Priority: Major
>             Fix For: 2.10.0, 3.2.0, 2.9.2, 3.0.4, 3.1.2
>
>         Attachments: HDFS-13821.001.patch, HDFS-13821.002.patch, 
> HDFS-13821.003.patch, HDFS-13821.004.patch, HDFS-13821.005.patch, 
> HDFS-13821.006.patch, HDFS-13821.007.patch, HDFS-13821.008.patch, 
> LocalCacheTest.java, image-2018-08-13-11-27-49-023.png
>
>
> When i test rbf, if found performance problem.
> I found that ProxyAvgTime From Ganglia is so high, i run jstack on Router and 
> get the following stack frames
> {quote}
>    java.lang.Thread.State: WAITING (parking)
>         at sun.misc.Unsafe.park(Native Method)
>         - parking to wait for  <0x00000005c264acd8> (a 
> java.util.concurrent.locks.ReentrantLock$NonfairSync)
>         at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
>         at 
> java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
>         at 
> java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
>         at 
> com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2249)
>         at 
> com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2228)
>         at com.google.common.cache.LocalCache.get(LocalCache.java:3965)
>         at 
> com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4764)
>         at 
> org.apache.hadoop.hdfs.server.federation.resolver.MountTableResolver.getDestinationForPath(MountTableResolver.java:380)
>         at 
> org.apache.hadoop.hdfs.server.federation.router.RouterRpcServer.getLocationsForPath(RouterRpcServer.java:2104)
>         at 
> org.apache.hadoop.hdfs.server.federation.router.RouterRpcServer.getLocationsForPath(RouterRpcServer.java:2087)
>         at 
> org.apache.hadoop.hdfs.server.federation.router.RouterRpcServer.getListing(RouterRpcServer.java:1050)
>         at 
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getListing(ClientNamenodeProtocolServerSideTranslatorPB.java:640)
>         at 
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
>         at 
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
>         at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2115)
>         at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2111)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at javax.security.auth.Subject.doAs(Subject.java:422)
> {quote}
> Many threads blocked on *LocalCache*
> After disable the cache, ProxyAvgTime is down as follow showed
>  !image-2018-08-13-11-27-49-023.png! 



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