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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Resolved] (CASSANDRA-6544) Reduce GC activity during compaction
Date Wed, 21 Jan 2015 22:14:36 GMT


Jonathan Ellis resolved CASSANDRA-6544.
    Resolution: Later
      Reviewer:   (was: Pavel Yaskevich)

Going to resolve as Later since this probably isn't the top concern in 2.1+ anymore.

> Reduce GC activity during compaction
> ------------------------------------
>                 Key: CASSANDRA-6544
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Vijay
>              Labels: compaction
>             Fix For: 2.1.3
> 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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