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https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13714403#comment-13714403
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Ben Manes commented on CASSANDRA-5661:
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Switching from LTQ to a custom elimination backoff stack appears to have
dropped the 98% to 179us. The single threaded benchmark improves by 30ns. A
significant gain was also observed when using an EBS instead of an array of
CLQs in the time-to-idle policy.
I'm surprised by how much of a gain occurs, so I'll have to experiment further
to understand if its factual. LTQ/CLQ are hindered by having to honor FIFO with
j.u.c. interfaces, and LIFO elimination is the ideal strategy for an object
pool. The more frequently successful exchanges may reduce down to eden-space
GC, resulting in major net wins. That, or I'm prematurely believing that its
working correctly.
> Discard pooled readers for cold data
> ------------------------------------
>
> Key: CASSANDRA-5661
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5661
> 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-multiway-per-sstable.patch,
> CASSANDRA-5661.patch, CASSANDRA-5661-v2-global-multiway-per-sstable.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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