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

[Romain PELISSE (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBTM-555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12467507#action_12467507 ] 

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

Maybe running the test with the gc.log and analysing it afterwards would also be a sounded approach ? 

Basically what is to know of the test is : "Is there memory consumption below a certain threshold ?", this could be answer by a gc.log file... (However, this is rather tied to the Sun JVM implementation).

Moreover, analysing the GC log also allow to see how the memory consumtion progress, maybe spotting a memory consumption rising (even if it's stay beneath the appropriate threshold during the test) that wasn't rising in the previous version. 

That gain this sort of knowledge would requires you to either run test on previous tag release or keep previous GC.log on file, however doing the first one with Git is not really that complicated (in fact, it will be similar to using the 'bissect' command).

On other "trick" that I know of is the Ant's for-each statement in the ant-contrib.jar, which will allow to do something like this:

<for-each ..>
      <junit .... >  <!-- run one particular test or test group -->
             <!-- Load memory configuration for an appropriate test from a properties file -->
             <property name="${testId}-config.."/>

             <jvmarg value="-Xms${memory.start}"/> 
            <jvmarg value="-Xmx${memory.max}"/> <!-- 
...

Hope that's help.

> 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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