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https://issues.apache.org/jira/browse/HBASE-8755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13770888#comment-13770888
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stack commented on HBASE-8755:
------------------------------
Just parking the numbers here. Takes same time to write 5x as much (5M
entries by 5 threads) as 1M entries by 1 thread. 50x takes 6x longer (50
threads writing 50M entries)
{code}
/tmp/log-patch1.1.txt:2013-09-17 21:19:31,495 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=1, iterations=1000000 took
991.258s 1008.819ops/s
/tmp/log-patch1.2.txt:2013-09-17 21:35:04,715 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=1, iterations=1000000 took
924.881s 1081.220ops/s
/tmp/log-patch1.3.txt:2013-09-17 21:51:32,416 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=1, iterations=1000000 took
979.312s 1021.125ops/s
/tmp/log-patch50.1.txt:2013-09-17 23:29:45,188 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=50, iterations=1000000 took
2960.095s 16891.350ops/s
/tmp/log-patch50.2.txt:2013-09-18 00:22:48,849 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=50, iterations=1000000 took
2924.844s 17094.930ops/s
/tmp/log-patch50.3.txt:2013-09-18 01:15:58,646 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=50, iterations=1000000 took
2927.617s 17078.736ops/s
/tmp/log-patch5.1.txt:2013-09-17 22:07:31,712 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=5, iterations=1000000 took
950.968s 5257.800ops/s
/tmp/log-patch5.2.txt:2013-09-17 22:23:39,680 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=5, iterations=1000000 took
939.312s 5323.045ops/s
/tmp/log-patch5.3.txt:2013-09-17 22:39:56,011 INFO [main]
wal.HLogPerformanceEvaluation: Summary: threads=5, iterations=1000000 took
947.183s 5278.811ops/s
{code}
> A new write thread model for HLog to improve the overall HBase write
> throughput
> -------------------------------------------------------------------------------
>
> Key: HBASE-8755
> URL: https://issues.apache.org/jira/browse/HBASE-8755
> Project: HBase
> Issue Type: Improvement
> Components: Performance, wal
> Reporter: Feng Honghua
> Assignee: stack
> Priority: Critical
> Fix For: 0.96.1
>
> Attachments: 8755trunkV2.txt, HBASE-8755-0.94-V0.patch,
> HBASE-8755-0.94-V1.patch, HBASE-8755-trunk-V0.patch, HBASE-8755-trunk-V1.patch
>
>
> In current write model, each write handler thread (executing put()) will
> individually go through a full 'append (hlog local buffer) => HLog writer
> append (write to hdfs) => HLog writer sync (sync hdfs)' cycle for each write,
> which incurs heavy race condition on updateLock and flushLock.
> The only optimization where checking if current syncTillHere > txid in
> expectation for other thread help write/sync its own txid to hdfs and
> omitting the write/sync actually help much less than expectation.
> Three of my colleagues(Ye Hangjun / Wu Zesheng / Zhang Peng) at Xiaomi
> proposed a new write thread model for writing hdfs sequence file and the
> prototype implementation shows a 4X improvement for throughput (from 17000 to
> 70000+).
> I apply this new write thread model in HLog and the performance test in our
> test cluster shows about 3X throughput improvement (from 12150 to 31520 for 1
> RS, from 22000 to 70000 for 5 RS), the 1 RS write throughput (1K row-size)
> even beats the one of BigTable (Precolator published in 2011 says Bigtable's
> write throughput then is 31002). I can provide the detailed performance test
> results if anyone is interested.
> The change for new write thread model is as below:
> 1> All put handler threads append the edits to HLog's local pending buffer;
> (it notifies AsyncWriter thread that there is new edits in local buffer)
> 2> All put handler threads wait in HLog.syncer() function for underlying
> threads to finish the sync that contains its txid;
> 3> An single AsyncWriter thread is responsible for retrieve all the buffered
> edits in HLog's local pending buffer and write to the hdfs
> (hlog.writer.append); (it notifies AsyncFlusher thread that there is new
> writes to hdfs that needs a sync)
> 4> An single AsyncFlusher thread is responsible for issuing a sync to hdfs
> to persist the writes by AsyncWriter; (it notifies the AsyncNotifier thread
> that sync watermark increases)
> 5> An single AsyncNotifier thread is responsible for notifying all pending
> put handler threads which are waiting in the HLog.syncer() function
> 6> No LogSyncer thread any more (since there is always
> AsyncWriter/AsyncFlusher threads do the same job it does)
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