RFR(M):8252103:parallel heap inspection for ParallelScavengeHeap
David Holmes
david.holmes at oracle.com
Tue Sep 1 04:44:04 UTC 2020
Hi Lin,
On 1/09/2020 12:28 pm, linzang(臧琳) wrote:
> Dear All,
>
> May I ask your help to review this change of adding parallel
> heap inspection for PSS Heap?
>
> bug: https://bugs.openjdk.java.net/browse/JDK-8252103
>
> webrev:
> http://cr.openjdk.java.net/~lzang/jmap-8214535/8252103/webrev.00/
>
> My preliminary measurement shows about ~1x speed up for when
> using 4 threads of jmap -histo. (on a 4 core Linux machine, with -xmx8g
> and objects takes 1.5GB in heap.)
~1x speed up is not a speed up. What exactly did you mean here?
Thanks,
David
-----
> As spaces in youngGen of parallelScvangeHeap is hard to be
> divided for parallel iteration, this change just assign different worker
> thread to process different space in youngGen, that is, 1 thread to
> process whole eden space etc. so this may be one reason that speedup is
> not scale with parallel thread number.
>
> BRs,
>
> Lin
>
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