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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-12475) Replace guava Cache with ConcurrentHashMap for caching Connection in ipc Client
Date Wed, 14 Oct 2015 06:08:05 GMT
Walter Su created HADOOP-12475:
----------------------------------

             Summary: Replace guava Cache with ConcurrentHashMap for caching Connection in
ipc Client
                 Key: HADOOP-12475
                 URL: https://issues.apache.org/jira/browse/HADOOP-12475
             Project: Hadoop Common
          Issue Type: Sub-task
            Reporter: Walter Su
            Assignee: Walter Su


quote [~daryn] from HADOOP-11772:
{quote}
CacheBuilder is obscenely expensive for concurrent map, and it requires generating unnecessary
garbage even just to look up a key. Replace it with ConcurrentHashMap.

I identified this issue that impaired my own perf testing under load. The slowdown isn't just
the sync. It's the expensive of Connection's ctor stalling other connections. The expensive
of ConnectionId#equals causes delays. Synch'ing on connections causes unfair contention unlike
a sync'ed method. Concurrency simply hides this.
{quote}

BTW, guava Cache is heavyweight. Per local test, ConcurrentHashMap has better overal performance.



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