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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (ACCUMULO-3508) Zoocache utilizes course grained locking causing unnecessary synchronization in many tserver ops
Date Mon, 06 Apr 2015 03:15:12 GMT

     [ https://issues.apache.org/jira/browse/ACCUMULO-3508?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Josh Elser updated ACCUMULO-3508:
---------------------------------
    Fix Version/s:     (was: 1.7.0)
                   1.7.1
                   1.8.0

> Zoocache utilizes course grained locking causing unnecessary synchronization in many
tserver ops
> ------------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-3508
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3508
>             Project: Accumulo
>          Issue Type: Sub-task
>          Components: fate
>    Affects Versions: 1.6.0
>            Reporter: marco polo
>            Assignee: marco polo
>            Priority: Minor
>             Fix For: 1.6.3, 1.8.0, 1.7.1
>
>
> Through jstacking I have observed busy tablet server threads waiting for the Zoocache
to be updated or even read. Profiling via yourkit indicates potential deadlocks when threads
wait for a long period of time ( in my case my waits were 10+s ) when many scans were running
against my instance.
> My patch, which is forthcoming, removes synchronization and utilizes a reentrant read/write
lock (RERWL) to synchronize the maps. My initial design utilized concurrent hash maps, but
the design of existence becomes simpler and changes fewer by using the RERWL. 



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