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From "Ryan McGuire (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4860) Estimated Row Cache Entry size incorrect (always 24?)
Date Thu, 28 Mar 2013 06:33:16 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13616101#comment-13616101
] 

Ryan McGuire commented on CASSANDRA-4860:
-----------------------------------------

Hi [~vijay2win@yahoo.com], I have not tweaked any row cache settings from the default. This
is in my cassandra.yaml:

{code}
# Maximum size of the row cache in memory.
# NOTE: if you reduce the size, you may not get you hottest keys loaded on startup.
#
# Default value is 0, to disable row caching.
row_cache_size_in_mb: 0
{code}

>From the description, it sounds like I should have row caching turned off, and yet this
code is still being run as evidenced by the change in performance by reverting your patch.
I don't yet have a deep understanding of the features involved here, so if you have any other
suggestions for things to test here, please let me know. Thanks!
                
> Estimated Row Cache Entry size incorrect (always 24?)
> -----------------------------------------------------
>
>                 Key: CASSANDRA-4860
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4860
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Chris Burroughs
>            Assignee: Vijay
>             Fix For: 1.2.0 beta 3
>
>         Attachments: 0001-CASSANDRA-4860-for-11.patch, 0001-CASSANDRA-4860.patch, trunk-4860-revert.patch
>
>
> After running for several hours the RowCacheSize was suspicious low (ie 70 something
MB)  I used  CASSANDRA-4859 to measure the size and number of entries on a node:
> In [3]: 1560504./65021
> Out[3]: 24.0
> In [4]: 2149464./89561
> Out[4]: 24.0
> In [6]: 7216096./300785
> Out[6]: 23.990877204647838
> That's RowCacheSize/RowCacheNumEntires  .  Just to prove I don't have crazy small rows
the mean size of the row *keys* in the saved cache is 67 and Compacted row mean size: 355.
 No jamm errors in the log
> Config notes:
> row_cache_provider: ConcurrentLinkedHashCacheProvider
> row_cache_size_in_mb: 2048
> Version info:
>  * C*: 1.1.6
>  * centos 2.6.32-220.13.1.el6.x86_64
>  * java 6u31 Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01, mixed mode)

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