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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-13082) Coarsen StoreScanner locks to RegionScanner
Date Tue, 24 Nov 2015 12:53:11 GMT

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

ramkrishna.s.vasudevan updated HBASE-13082:
-------------------------------------------
    Attachment: HBASE-13082_17.patch

Updated patch.  The refCounting is still in the Storefile because that is where we create
the scanner and close the scanner. The SFM is not involved in that. But now added markCompactedAway()
in SFM and once the compactedREsults are added to the SFM we call this API from the compact()
F/W. So that in future any impl of the compaction logic can do this marking. 


> Coarsen StoreScanner locks to RegionScanner
> -------------------------------------------
>
>                 Key: HBASE-13082
>                 URL: https://issues.apache.org/jira/browse/HBASE-13082
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: ramkrishna.s.vasudevan
>         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_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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