RFR (T): 8211211: vmTestbase/metaspace/stressDictionary/StressDictionary.java timeout

sangheon.kim at oracle.com sangheon.kim at oracle.com
Tue Nov 27 23:04:29 UTC 2018


Hi Thomas,

On 11/27/18 3:38 AM, Thomas Schatzl wrote:
> Hi all,
>
>    can I have reviews for this trivial change to the test in the subject
> to avoid timeouts due to some metaspace verification being very slow?
>
> This tests creates hundreds/thousands of classes to be unloaded. Class
> unloading, and in particular metaspace freeing has some very nasty and
> slow verification code (basically O(n^2)).
>
> This problem is particular problematic with CMS with precleaning, which
> basically delays remark for 5 seconds (until it times out), during
> which the test continues to add more and more metadata that takes very
> long to clean out. I.e. that n is rather large.
>
> The other collectors have a much shorter turnaround time, so n is much
> smaller, and the slow metaspace verification code is not problematic.
>
> This change fixes the test to disable CMS precleaning, avoiding that n
> gets too large.
>
> I filed JDK-8214356 to look into shortening the actual metaspace
> verification process.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8211211
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8211211/webrev/
Both webrev and plan to fix look good.

Thanks,
Sangheon


> Testing:
> Running the test in CI with CMS enabled (and disabled), now takes as
> long as with the other collectors
>
> Thanks,
>    Thomas
>



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