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https://issues.apache.org/jira/browse/HBASE-16890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15639495#comment-15639495
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Duo Zhang commented on HBASE-16890:
-----------------------------------
Think of this scenario. 10 thread do append and sync sequentiallly, and the
background task is fast enough and can process the request one by one, so we
will issue an actual hflush for every sync request. Now the DN is blocked by a
long gc. For FSHLog, we only have five threads to do hflush so when we have
five hflush being blocked, then we will be blocked until the DN recoved and
then we will send all the pending data with one packet(maybe multiple packets
but at least the packets Will be large enough). But for AsyncFSWAL, nothing
changes. We Will still issue a hflush for every sync request.
Is This clear enough? Thanks.
> Analyze the performance of AsyncWAL and fix the same
> ----------------------------------------------------
>
> Key: HBASE-16890
> URL: https://issues.apache.org/jira/browse/HBASE-16890
> Project: HBase
> Issue Type: Sub-task
> Components: wal
> Affects Versions: 2.0.0
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Fix For: 2.0.0
>
> Attachments: AsyncWAL_disruptor.patch, AsyncWAL_disruptor_1
> (2).patch, AsyncWAL_disruptor_3.patch, AsyncWAL_disruptor_3.patch,
> AsyncWAL_disruptor_4.patch, AsyncWAL_disruptor_6.patch,
> HBASE-16890-rc-v2.patch, HBASE-16890-rc-v3.patch,
> HBASE-16890-remove-contention-v1.patch, HBASE-16890-remove-contention.patch,
> Screen Shot 2016-10-25 at 7.34.47 PM.png, Screen Shot 2016-10-25 at 7.39.07
> PM.png, Screen Shot 2016-10-25 at 7.39.48 PM.png, Screen Shot 2016-11-04 at
> 5.21.27 PM.png, Screen Shot 2016-11-04 at 5.30.18 PM.png, async.svg,
> classic.svg, contention.png, contention_defaultWAL.png
>
>
> Tests reveal that AsyncWAL under load in single node cluster performs slower
> than the Default WAL. This task is to analyze and see if we could fix it.
> See some discussions in the tail of JIRA HBASE-15536.
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