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From "Dominik Stadler (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (XMLBEANS-525) Reduce locking/contention in Path.getCompiledPath()
Date Sun, 03 Mar 2019 09:11:00 GMT

     [ https://issues.apache.org/jira/browse/XMLBEANS-525?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Dominik Stadler resolved XMLBEANS-525.
       Resolution: Won't Fix
         Assignee: Dominik Stadler
    Fix Version/s: unspecified

Contention did not show any more in subsequent tests so it seems the initial setup was maybe
too limit in memory/hardware to be a valid test-setup.

> Reduce locking/contention in Path.getCompiledPath()
> ---------------------------------------------------
>                 Key: XMLBEANS-525
>                 URL: https://issues.apache.org/jira/browse/XMLBEANS-525
>             Project: XMLBeans
>          Issue Type: Improvement
>    Affects Versions: Version 3.0.2
>            Reporter: Dominik Stadler
>            Assignee: Dominik Stadler
>            Priority: Critical
>              Labels: 303-candidate
>             Fix For: unspecified
> When running the large regression test-suite for Apache POI with multiple threads (each
working on a single file), I saw that the lock in Path.getCompiledPath() is causing big contention,
keeping the test from utilizing multiple CPU cores fully.
> I tested with manually disabling this locking completely, then CPU is utilized much better,
however there are potential race-conditions for the static maps.
> It seems in this case where we process a huge amount of different files, write-locks
do occur constantly, i.e. there are always new expressions being put into the cache and thus
write-locks do occur and keep other threads from accessing the cache.
> Possible options:
>  * test with using using more fine-grained locking on each map separately
>  * maybe we can use concurrent maps and Java 8 Map.computeIfAbsent() directly instead
of the lock-get-put-unlock combination.
>  * Add an option to make the caches per thread via thread-local so no locking is needed
any more
>  * ?

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