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https://issues.apache.org/jira/browse/HBASE-8755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13761065#comment-13761065
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stack commented on HBASE-8755:
------------------------------
Staring in on taking a look at this. I tried HLogPerformanceEvaluation. Going
via ycsb would seem to add noise and indirection. I ran with 1, 5, and 50
threads w/ sizes that are like Honghua's (key of 50 and value of 150).
I ran the test like this on trunk using localfs:
{code}
$ for i in 1 5 50; do for j in 1 2 3; do ./bin/hbase
org.apache.hadoop.hbase.regionserver.wal.HLogPerformanceEvaluation -verify
-threads "${i}" -iterations 1000000 -nocleanup -verbose -keySize 50 -valueSize
100 &> /tmp/log-patch"${i}"."${j}".txt; done; done
{code}
Needs fixes over in HBASE-9460 for above to work on localfs.
With localfs, the patch is twice as slow. localfs does not support sync so
this is probably what makes the difference -- the extra threads do better w/
the dfsclient's stutter around sync. Let me try up on hdfs next.
Below are numbers. I ran each test three times: i.e. three times without patch
with one thread, then three times with patch and one thread, etc.
Each thread did 1M puts. The table is times for the test to complete in
seconds so less is better.
||Thread Count||WithoutPatch||WithPatch||
|1|4.895|29.088|
|1|4.856|29.544|
|1|4.901|29.326|
|5|24.173|53.974|
|5|24.013|55.976|
|5|23.390|55.858|
|50|253.773|454.147|
|50|247.095|443.215|
|50|254.044|449.043|
> 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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