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https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13701511#comment-13701511
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Jonathan Ellis commented on CASSANDRA-5661:
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Perhaps it will help if I recap:
# CRAR pooling + LCS OOMs us at relatively small amounts of data (20GB in
Jeremiah's example)
# worst case pool size proportional to sstables * concurrent readers means that
memory usage increases linearly with disk size; increasing sstable size
decreases it linearly, so we expect 100MB sstables [which is on the high side
of what is reasonable IMO] to get us to ~4TB of space managed which is good but
not "problem solved" territory.
# thus, we need to bound CRAR pooling and not just say "it's working as
designed, go use larger sstables or STCS" [although that is probably adequate
for 1.2, so I am tagging this for 2.0]
# The most common operations in an object pool are the borrow/return. Ben's
multiway pool optimizes for this, with particular attention to possible
contention from multiple reader threads.
# The multiway pool supports expiring objects after they have been idle for a
given time, as well as a total pool size.
> 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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