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From "Vladimir Rodionov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10015) Major performance improvement: Avoid synchronization in StoreScanner
Date Sat, 23 Nov 2013 01:30:36 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13830496#comment-13830496
] 

Vladimir Rodionov commented on HBASE-10015:
-------------------------------------------

{quote}
 so there is potential for a lot more improvements
{quote}

KV creation (new) is one of the serious bottlenecks, but I have no idea how to not create
new instances on *next*. I have done some HBase internal hacks to get Maximum possible performance
from scan. It is the multi-threaded  application (in my case - 8HT threads) and scans on StoreFileScanner
directly (data is cached 100%).  The table was tall and narrow.

Stock HBase was able to reach 50M KV per sec
Stock with KV reuse (hack) - 90M KV per sec.




> Major performance improvement: Avoid synchronization in StoreScanner
> --------------------------------------------------------------------
>
>                 Key: HBASE-10015
>                 URL: https://issues.apache.org/jira/browse/HBASE-10015
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.98.0, 0.96.1, 0.94.15
>
>         Attachments: 10015-0.94-v2.txt, 10015-0.94-v3.txt, 10015-0.94-v4.txt, 10015-0.94-withtest.txt,
10015-0.94.txt, 10015-trunk-v2.txt, 10015-trunk-v3.txt, 10015-trunk-v4.txt, 10015-trunk-v4.txt,
10015-trunk-v4.txt, 10015-trunk.txt, TestLoad.java
>
>
> Did some more profiling (this time with a sampling profiler) and StoreScanner.peek()
showed up a lot in the samples. At first that was surprising, but peek is synchronized, so
it seems a lot of the sync'ing cost is eaten there.
> It seems the only reason we have to synchronize all these methods is because a concurrent
flush or compaction can change the scanner stack, other than that only a single thread should
access a StoreScanner at any given time.
> So replaced updateReaders() with some code that just indicates to the scanner that the
readers should be updated and then make it the using thread's responsibility to do the work.
> The perf improvement from this is staggering. I am seeing somewhere around 3x scan performance
improvement across all scenarios.
> Now, the hard part is to reason about whether this is 100% correct. I ran TestAtomicOperation
and TestAcidGuarantees a few times in a loop, all still pass.
> Will attach a sample patch.



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