hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Liyin Tang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3694) high multiput latency due to checking global mem store size in a synchronized function
Date Wed, 23 Mar 2011 22:33:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010492#comment-13010492
] 

Liyin Tang commented on HBASE-3694:
-----------------------------------

We tried to add this var in RS and passing it to Region via its constructor at the beginning.
However since the HRegion is not created by RS, it is hard to implement and it will pass the
NULL to the HRegion constructor in most cases. 
Of course, we can set the RegionServer reference to the Regions every time, but it will make
the code much more complicated. 

As long as this change ONLY conflicts with some unit tests, we can make it work for that case.

For example, we can write a function in minicluster tests to get the global mem store size
for the given Region Server.

Any Thoughts:)

Liyin



> high multiput latency due to checking global mem store size in a synchronized function
> --------------------------------------------------------------------------------------
>
>                 Key: HBASE-3694
>                 URL: https://issues.apache.org/jira/browse/HBASE-3694
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Liyin Tang
>            Assignee: Liyin Tang
>
> The problem is we found the multiput latency is very high.
> In our case, we have almost 22 Regions in each RS and there are no flush happened during
these puts.
> After investigation, we believe that the root cause is the function getGlobalMemStoreSize,
which is to check the high water mark of mem store. 
> This function takes almost 40% of total execution time of multiput when instrumenting
some metrics in the code.  
> The actual percentage may be more higher. The execution time is spent on synchronize
contention.
> One solution is to keep a static var in HRegion to keep the global MemStore size instead
of calculating them every time.
> Why using static variable?
> Since all the HRegion objects in the same JVM share the same memory heap, they need to
share fate as well.
> The static variable, globalMemStroeSize, naturally shows the total mem usage in this
shared memory heap for this JVM.
> If multiple RS need to run in the same JVM, they still need only one globalMemStroeSize.
> If multiple RS run on different JVMs, everything is fine.
> After changing, in our cases, the avg multiput latency decrease from 60ms to 10ms.
> I will submit a patch based on the current trunk.

--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message