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https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14351034#comment-14351034
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Hudson commented on HBASE-13082:
--------------------------------
FAILURE: Integrated in HBase-TRUNK #6217 (See
[https://builds.apache.org/job/HBase-TRUNK/6217/])
HBASE-13082 Coarsen StoreScanner locks to RegionScanner. (larsh: rev
ec1eff9b69d37d2340f057361d2b269cc5fffd56)
*
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueScanner.java
*
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileScanner.java
*
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
*
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/NonLazyKeyValueScanner.java
*
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ReversedStoreScanner.java
* hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
> 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: Lars Hofhansl
> Fix For: 2.0.0, 1.1.0
>
> Attachments: 13082-test.txt, 13082.txt, 13082.txt, 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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