Generational ZGC crashes on specbjbb

[Erik Osterlund]

Hi Liang,

Thank you for the feedback. This was very helpful feedback. It suddenly explains so much.
I didn’t implement AVX512 arraycopy intrinsics for generational ZGC, so instead I had a hook
to bail out of conjoint and disjoint AVX512 arraycopy. Recently, the arraycopy code moved to
a new file, and it looks like only one of those too points survived a recent merge merge. We
are missing the one for conjoint AVX512 arraycopy. Whe run a lot on Skylake, where AVX512
is disabled by default. When it is enabled, we can suddenly reproduce the same crashes on
Skylake too.

I have pushed a fix for this issue.

Thanks,
/Erik

On 31 Oct 2022, at 04:35, Liang Mao <maoliang.ml at alibaba-inc.com<mailto:maoliang.ml at alibaba-inc.com>> wrote:

Hi Stefan and ZGC team,

I see crashes as well with early access build. The command line is
"java -XX:+UseZGC -Xmx8g -Xms8g -Xlog:gc* -XX:ParallelGCThreads=8 -XX:ConcGCThreads=2 -jar specjbb2015.jar -m COMPOSITE".
It works well in Intel sky-lake machines but consistently crashes in an Ice-lake architecture
"Intel(R) Xeon(R) Platinum 8369B CPU @ 2.90GHz" machine in 3 minutes. Hope this can help.

Thanks,
Liang




------------------------------------------------------------------
From:Stefan Karlsson <stefan.karlsson at oracle.com<mailto:stefan.karlsson at oracle.com>>
Send Time:2022 Oct. 19 (Wed.) 19:44
To:"Kemper, William" <kemperw at amazon.com<mailto:kemperw at amazon.com>>; zgc-dev at openjdk.org<mailto:zgc-dev at openjdk.org> <zgc-dev at openjdk.org<mailto:zgc-dev at openjdk.org>>
Subject:Re: Generational ZGC crashes on specbjbb

Thanks a lot!

I'll see if I can figure out a way to reproduce this in-house.

StefanK

On 2022-10-18 23:39, Kemper, William wrote:
Filed: https://bugs.openjdk.org/browse/JDK-8295532 - Please let me know if you need anymore data. We're excited about Generational ZGC!

William
________________________________
From: Stefan Karlsson <stefan.karlsson at oracle.com><mailto:stefan.karlsson at oracle.com>
Sent: Tuesday, October 18, 2022 11:57:47 AM
To: Kemper, William; zgc-dev at openjdk.org<mailto:zgc-dev at openjdk.org>
Subject: RE: [EXTERNAL]Generational ZGC crashes on specbjbb

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Thanks for reporting. If you file a JBS entry I'll figure out the best way to tag issues around Generational ZGC.

Thanks,
StefanK

On 2022-10-18 20:20, Kemper, William wrote:
How do you want to handle error reports? I didn't see how to open an issue on GitHub. Should I open a ticket on JBS? Is there a label to distinguish ZGC generational from non-generational?

Thank you,
William




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