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From "Branimir Lambov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5863) In process (uncompressed) page cache
Date Tue, 22 Mar 2016 15:42:26 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15206596#comment-15206596
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Branimir Lambov commented on CASSANDRA-5863:
--------------------------------------------

bq. Can you re-run the stress with 500 threads vs 50 to see what it looks like under some
load?

The run is [here|http://cstar.datastax.com/tests/id/2324a078-f040-11e5-8634-0256e416528f].
This time the 8G run is only as fast as the 480M one; this may be because this many threads
need more memory and we reserve 8G but only use 0.85 (this can be found in the nodetool info
output). Room for improvement there.

> In process (uncompressed) page cache
> ------------------------------------
>
>                 Key: CASSANDRA-5863
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5863
>             Project: Cassandra
>          Issue Type: Sub-task
>            Reporter: T Jake Luciani
>            Assignee: Branimir Lambov
>              Labels: performance
>             Fix For: 3.x
>
>
> Currently, for every read, the CRAR reads each compressed chunk into a byte[], sends
it to ICompressor, gets back another byte[] and verifies a checksum.  
> This process is where the majority of time is spent in a read request.  
> Before compression, we would have zero-copy of data and could respond directly from the
page-cache.
> It would be useful to have some kind of Chunk cache that could speed up this process
for hot data, possibly off heap.



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