[jira] [Created] (HBASE-15453) Considering reverting HBASE-10015 - reinstance synchronized in StoreScanner

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

Lars Hofhansl created HBASE-15453:
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             Summary: Considering reverting HBASE-10015 - reinstance synchronized in StoreScanner
                 Key: HBASE-15453
                 URL: https://issues.apache.org/jira/browse/HBASE-15453
             Project: HBase
          Issue Type: Bug
            Reporter: Lars Hofhansl


In HBASE-10015 back then I found that intrinsic locks (synchronized) in StoreScanner are slower that explicit locks.

I was surprised by this. To make sure I added a simple perf test and many folks ran it on their machines. All found that explicit locks were faster.

Now... I just ran that test again. On the latest JDK8 I find that now the intrinsic locks are significantly faster:

Explicit locks:
10 runs  mean:2223.6 sigma:72.29412147609237

Intrinsic locks:
10 runs  mean:1865.3 sigma:32.63755505548784

I confirmed the same with timing some Phoenix scans. We can save a bunch of time by changing this back 

Arrghhh... So maybe it's time to revert this now...?

(Note that in trunk due to [~ram_krish]'s work, we do not lock in StoreScanner anymore)

I'll attach the perf test and a patch that changes lock to synchronized, if some folks could run this on 0.98, that'd be great.




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