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https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13701523#comment-13701523
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Pavel Yaskevich commented on CASSANDRA-5661:
--------------------------------------------
[~ben.manes] I briefly looked through the code and I think there is an
important component missing - we need to weight size of the cache based on
internal structure of each object allocated into it (borrowed) as the biggest
part would be in memory buffer that each instance holds, so simple number of
entries wouldn't do...
I'm worried that getResourceHandler has to go through few queues and
allocation, I wanted to avoid polling + atomic CAS on read path, which is most
critical, as much as possible because it adds additional undesired latency
especially to high cardinality requests.
Also I don't think using just weak references to remove unused queues is a good
idea (if I interpreted comment at the top correctly), we need something more
agressive, because ParNew+CMS only processes those in FullGC phrase even when
objects effectively die in young gen (sun/open jdk) and G1 doesn't even have
any guarantees on when they are going to be processed, not mentioning that it
requires double pass.
> 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: 1.2.7
>
> Attachments: 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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