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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-7154) Should set MALLOC_ARENA_MAX in hadoop-env.sh
Date Fri, 25 Feb 2011 00:49:43 GMT
Should set MALLOC_ARENA_MAX in hadoop-env.sh

                 Key: HADOOP-7154
                 URL: https://issues.apache.org/jira/browse/HADOOP-7154
             Project: Hadoop Common
          Issue Type: Improvement
          Components: scripts
    Affects Versions: 0.22.0
            Reporter: Todd Lipcon
            Assignee: Todd Lipcon
            Priority: Minor
             Fix For: 0.22.0

New versions of glibc present in RHEL6 include a new arena allocator design. In several clusters
we've seen this new allocator cause huge amounts of virtual memory to be used, since when
multiple threads perform allocations, they each get their own memory arena. On a 64-bit system,
these arenas are 64M mappings, and the maximum number of arenas is 8 times the number of cores.
We've observed a DN process using 14GB of vmem for only 300M of resident set. This causes
all kinds of nasty issues for obvious reasons.

Setting MALLOC_ARENA_MAX to a low number will restrict the number of memory arenas and bound
the virtual memory, with no noticeable downside in performance - we've been recommending MALLOC_ARENA_MAX=4.
We should set this in hadoop-env.sh to avoid this issue as RHEL6 becomes more and more common.

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