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From "Vijay (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-6544) Reduce GC activity during compaction
Date Tue, 07 Jan 2014 22:06:50 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13864746#comment-13864746
] 

Vijay edited comment on CASSANDRA-6544 at 1/7/14 10:05 PM:
-----------------------------------------------------------

Hi Jonathan, Yep in addition... if we can create a a offheap slab allocator (and reuse the
slabs) it will help in reducing the memory fragmentation. Hope that make sense.


was (Author: vijay2win@yahoo.com):
Hi Jonathan, Yep in addition... if we can create a a offheap slab allocator (and reuse the
slabs) it will help in reducing the memory fragmentation. Hope that make sure.

> Reduce GC activity during compaction
> ------------------------------------
>
>                 Key: CASSANDRA-6544
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6544
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Vijay
>            Assignee: Vijay
>             Fix For: 2.1
>
>
> We are noticing increase in P99 while the compactions are running at full stream. Most
of it is because of the increased GC activity (followed by full GC).
> The obvious solution/work around is to throttle the compactions, but with SSD's we can
get more disk bandwidth for reads and compactions.
> It will be nice to move the compaction object allocations off heap. First thing to do
might be create a Offheap Slab allocator with the size as the compaction in memory size and
recycle it. 
> Also we might want to make it configurable so folks can disable it when they don't have
off-heap memory to reserve.



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