RFR(M):8252103:parallel heap inspection for ParallelScavengeHeap(Internet mail)
linzang(臧琳)
linzang at tencent.com
Tue Sep 1 04:53:34 UTC 2020
Hi David,
My mistake, it should be 2x faster with this patch, Thanks for point it out!
Raw data of Jmap histo (Average of 5 times run)
Before: 685ms
After(4threads): 356ms
BRs,
Lin
> On Sep 1, 2020, at 12:45 PM, David Holmes <david.holmes at oracle.com> wrote:
>
> 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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