RFR(M):8252103:parallel heap inspection for ParallelScavengeHeap

[David Holmes]

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
>