RFR (M): 8157952: Parallelize Memory Pretouch

Vitaly Davidovich vitalyd at gmail.com
Wed Sep 7 10:54:43 UTC 2016


Hi Thomas,

Why does the G1PretouchTask use an atomic ptr add to advance the touch
address?

Thanks
On Wed, Sep 7, 2016 at 4:08 AM Thomas Schatzl <thomas.schatzl at oracle.com>
wrote:

> Hi all,
>
>   can I have reviews for this change that parallelizes memory pretouch?
> Particularly on large systems (like hundreds of GB) this often improves
> startup time by an order of magnitude.
>
> Like in some systems with 1TB+ heap I have running from 12mins to
> ~1min.
>
> It does so by having multiple threads doing the pretouching, using more
> of the available memory bandwidth of the computer.
>
> This change only has an FC extension approval by the group lead for
> now, but I expect to get the release teams' approval soon.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8157952
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8157952/webrev
> Testing:
> jprt, vm.gc run with -XX:+AlwaysPreTouch, nightly test suite run
>
> Thanks,
>   Thomas
>
>
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