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From "Ben Manes (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-5661) Discard pooled readers for cold data
Date Thu, 08 Aug 2013 18:50:48 GMT


Ben Manes commented on CASSANDRA-5661:

My benchmark had a bug and EBS may only be on par with LTQ performance wise. I need to investigate
that again, though.

I shifted focus to fixing the performance bottleneck in Guava's cache. The way we tracked
usage history (e.g. LRU) was focused on common usage, but is a bottleneck on synthetic benchmarks.
I made the fixes to CLHM (v1.4) and offered them upstream (issue 1487). I'll experiment with
using CLHM instead to see if that removes the hotspot.
> Discard pooled readers for cold data
> ------------------------------------
>                 Key: CASSANDRA-5661
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.2.1
>            Reporter: Jonathan Ellis
>            Assignee: Pavel Yaskevich
>             Fix For: 2.0.1
>         Attachments: CASSANDRA-5661-global-multiway-cache.patch, CASSANDRA-5661.patch,
DominatorTree.png, Histogram.png
> Reader pooling was introduced in CASSANDRA-4942 but pooled RandomAccessReaders are never
cleaned up until the SSTableReader is closed.  So memory use is "the worst case simultaneous
RAR we had open for this file, forever."
> We should introduce a global limit on how much memory to use for RAR, and evict old ones.

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