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From "Peter Schuller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2594) run cassandra under numactl --interleave=all
Date Tue, 03 May 2011 16:19:03 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2594?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028291#comment-13028291
] 

Peter Schuller commented on CASSANDRA-2594:
-------------------------------------------

If you wish to see how things are balanced on production systems, 'numactl -H' should show
you. For example:


available: 2 nodes (0-1)
node 0 cpus: 0 2 4 6 8 10 12 14
node 0 size: 24576 MB
node 0 free: 41 MB
node 1 cpus: 1 3 5 7 9 11 13 15
node 1 size: 24566 MB
node 1 free: 3573 MB
node distances:
node   0   1 
  0:  10  20 
  1:  20  10 


> run cassandra under numactl --interleave=all
> --------------------------------------------
>
>                 Key: CASSANDRA-2594
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2594
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Peter Schuller
>            Assignee: Peter Schuller
>            Priority: Minor
>         Attachments: CASSANDRA-2594-trunkk.txt
>
>
> By default, Linux attempts to be smart about memory allocations such that data is close
to the NUMA node on which it runs. For big database type of applications, this is not the
best thing to do if the priority is to avoid disk I/O. In particular with Cassandra, we're
heavily multi-threaded anyway and there is no particular reason to believe that one NUMA node
is "better" than another.
> Consequences of allocating unevenly among NUMA nodes can include excessive page cache
eviction when the kernel tries to allocate memory - such as when restarting the JVM.
> With that briefly stated background, I propse the following patch to make the Cassandra
script run Cassandra with numactl --interleave=all if numactl seems to be available.

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