[jbossts-issues] [JBoss JIRA] Commented: (JBTM-555) make memory leak tests more robust

Romain PELISSE (JIRA) jira-events at lists.jboss.org
Thu May 14 09:10:48 EDT 2009


    [ https://jira.jboss.org/jira/browse/JBTM-555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12467530#action_12467530 ] 

Romain PELISSE commented on JBTM-555:
-------------------------------------

Well, unless I mistaken, GC is almost always running, what is not always doing is cleaning the memory,at least not all memory, for this we have to wait for a full GC, which is I think what you want to trigger... 

What I'm suggesting is not really trying to get help from whatever the GC can do, but comparing memory consumption between releases, to see if some test now seems to be more memory consuming than before. This is more an other approach to the situation (how can detect memory leak) rather than a fix for the issue (find a way to trigger a full GC so jvm cleans the all memory).



> make memory leak tests more robust
> ----------------------------------
>
>                 Key: JBTM-555
>                 URL: https://jira.jboss.org/jira/browse/JBTM-555
>             Project: JBoss Transaction Manager
>          Issue Type: Task
>      Security Level: Public(Everyone can see) 
>          Components: Testing, Transaction Core
>    Affects Versions: 4.6.1
>            Reporter: Jonathan Halliday
>            Assignee: Jonathan Halliday
>             Fix For: future
>
>
> Some tests in the txcore group attempt to detect memory leaks by
> setup
> System.gc()
> take memory reading
> doTransactionStuff
> System.gc()
> take another memory reading
> This is unreliable, as System.gc() is only advisory to the runtime. There is no way to FORCE gc from within the jvm. This causes the tests to be somewhat unreliable.
> Dirty tricks to work around this include running the tests with a small heap (-Xmx5m). With less free space to work with, the gc tries harder. On a default size heap it mostly ignores System.gc().  Unfortunately the test framework does not make it easy to set -Xmx on a per test / test group basis.
> Similar effect could perhaps be achieved by allocating all except a small portion of the available heap from within the vm using eg. new byte[].
> There is also the jvmti ForceGarbageCollection method, but that would require us to have a chunk of C code on each test platform, which is a pain.

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