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Posted to issues@hbase.apache.org by "stack (JIRA)" <ji...@apache.org> on 2016/01/22 19:45:39 UTC
[jira] [Resolved] (HBASE-13082) Coarsen StoreScanner locks to
RegionScanner
[ https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
stack resolved HBASE-13082.
---------------------------
Resolution: Fixed
Reresolving. Wrong issue. Meant to do the backport issue.
> 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, 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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