RFR: 8191821: Finer granularity for GC verification
Poonam Parhar
poonam.bajaj at oracle.com
Tue Nov 28 22:17:14 UTC 2017
Hello Stefan,
The changes look good! Thanks for implementing this enhancement.
One observation:
gcArguments.cpp: if we use VerifyGCType with the collectors that
currently don't support it, passing it multiple comma separated strings,
then parse_verification_type() will print this warning message
"VerifyGCType is not supported by this collector." for all the strings.
It would be better to break out from the while loop in
post_heap_initialize() if the collector does not support this option.
Thanks,
Poonam
On 11/28/2017 8:25 AM, Stefan Johansson wrote:
> Hi,
>
> Please review this change for enhancement:
> https://bugs.openjdk.java.net/browse/JDK-8191821
>
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8191821/00/
>
> Summary:
> Heap verification is a very good way to track down GC bugs, but it
> comes with a lot of overhead. Using VerifyBeforeGC, VerifyDuringGC and
> VerifyAfterGC often slows down the execution more than is needed since
> we sometimes only want to verify certain types of GCs. This change
> adds this feature for G1 by adding a new diagnostic flag VerifyGCType.
> The new flag currently only works with G1 but can easily be added for
> more GCs if needed. The type of the flag is ccstrlist which means the
> option can be used multiple times to allow more than one type to be
> verified. The types available for G1 is, young, mixed, remark, cleanup
> and full. If the flag is not specified all GCs are verified.
>
> Note that Verify/Before/After/During/GC is still needed to decide what
> to verify, VerifyGCType only describes when.
>
> Testing:
> * Added new Gtest for G1HeapVerifier functionality.
> * Added new Jtreg test for basic command line functionality.
> * Executed Jtreg tests through mach5 to make sure it passes on all
> platforms.
>
> Thanks,
> Stefan
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