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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (HBASE-13082) Coarsen StoreScanner locks to RegionScanner
Date Fri, 22 Jan 2016 18:38:40 GMT

     [ https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

stack reopened HBASE-13082:

Reopening. This commit introduces a test that fails reliably. Git bisect fingers this commit:

58521869b06a63894e422e9c9403e48b4b12f388 is the first bad commit
commit 58521869b06a63894e422e9c9403e48b4b12f388
Author: ramkrishna <ramkrishna.s.vasudevan@gmail.com>
Date:   Thu Jan 21 21:22:40 2016 +0530

    HBASE-14970 Backport HBASE-13082 and its sub-jira to branch-1 (Ram)

:040000 040000 ac9ba8c501616a32632f7b46adfe0afb7073458b 140cac3904b52a7d599e20f21c8d55961847ca77
M	hbase-client
:040000 040000 f3f53edf84a0f7885dcc577159ba5bbc1a8c6922 7c023622983f3bc4d9c1a43b2dd52c7d2d181b51
M	hbase-server

Here is my little test:

mvn clean install -DskipTests && mvn test -Dtest=TestHFileOutputFormat

Let me revert for now since its your w/e [~ram_krish]

> Coarsen StoreScanner locks to RegionScanner
> -------------------------------------------
>                 Key: HBASE-13082
>                 URL: https://issues.apache.org/jira/browse/HBASE-13082
>             Project: HBase
>          Issue Type: Bug
>          Components: Performance, Scanners
>            Reporter: Lars Hofhansl
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 2.0.0
>         Attachments: 13082-test.txt, 13082-v2.txt, 13082-v3.txt, 13082-v4.txt, 13082.txt,
13082.txt, HBASE-13082.pdf, HBASE-13082_1.pdf, HBASE-13082_12.patch, HBASE-13082_13.patch,
HBASE-13082_14.patch, HBASE-13082_15.patch, HBASE-13082_16.patch, HBASE-13082_17.patch, HBASE-13082_18.patch,
HBASE-13082_19.patch, HBASE-13082_1_WIP.patch, HBASE-13082_2.pdf, HBASE-13082_2_WIP.patch,
HBASE-13082_3.patch, HBASE-13082_4.patch, HBASE-13082_9.patch, HBASE-13082_9.patch, HBASE-13082_withoutpatch.jpg,
HBASE-13082_withpatch.jpg, LockVsSynchronized.java, gc.png, gc.png, gc.png, hits.png, next.png,
> Continuing where HBASE-10015 left of.
> We can avoid locking (and memory fencing) inside StoreScanner by deferring to the lock
already held by the RegionScanner.
> In tests this shows quite a scan improvement and reduced CPU (the fences make the cores
wait for memory fetches).
> There are some drawbacks too:
> * All calls to RegionScanner need to be remain synchronized
> * Implementors of coprocessors need to be diligent in following the locking contract.
For example Phoenix does not lock RegionScanner.nextRaw() and required in the documentation
(not picking on Phoenix, this one is my fault as I told them it's OK)
> * possible starving of flushes and compaction with heavy read load. RegionScanner operations
would keep getting the locks and the flushes/compactions would not be able finalize the set
of files.
> I'll have a patch soon.

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