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From "Ben Manes (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5661) Discard pooled readers for cold data
Date Sun, 14 Jul 2013 06:58:50 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13707974#comment-13707974
] 

Ben Manes commented on CASSANDRA-5661:
--------------------------------------

In a simple single-threaded benchmark, LTQ is relatively on par within the object pool.

Currently I have a finalizer on the handle as a safety net, both to catch my bugs and usage
mistakes. This includes a note on the performance impact, which appears to have add 2.5x overhead.
I had intended to replace this with phantom references instead, though now I'm wondering if
I should not put any safety net in whatsoever.

# Finalizer
queueType  ns linear runtime
      ABQ 489 =========================
      SAQ 545 ============================
      CLQ 535 ===========================
      LBQ 578 ==============================
      LTQ 555 ============================
      LBD 490 =========================

# No finalizer
queueType  ns linear runtime
      ABQ 176 =========================
      SAQ 159 ======================
      CLQ 166 =======================
      LBQ 210 ==============================
      LTQ 183 ==========================
      LBD 181 =========================

                
> 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
>
>         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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