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https://issues.apache.org/jira/browse/HBASE-10015?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Hofhansl updated HBASE-10015:
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Attachment: TestLoad.java
Test code. This is some crap extracted from various tests, don't judge me on
that code.. I will deny that I've ever written that.
Use it with TestLoad <tableName>. It will create and seed the table if needed.
Then it runs the scan tests 5 times (after a prime round) and calculates mean
and standard deviation.
Did I mention that this is hack? :)
For the record, I see a 2-3x scan speed improvement on both OpenJDK7 on a
old'ish 2 core machine as well as with Oracle JDK6 on a 12 core machine. In
both cases the scan is from a single client only.
> 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
> Attachments: 10015-0.94.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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