RFR (XS): 8150952: Net PLAB size is clipped to max PLAB size as a whole, not on a per thread basis
thomas.schatzl at oracle.com
Thu Mar 10 13:16:36 UTC 2016
could I have a "R"eviewer review for this change?
On Thu, 2016-03-03 at 15:07 +0100, Thomas Schatzl wrote:
> Hi all,
> can I have reviews for this change that fixes PLAB sizing clipping
> after we changed the desired PLAB size to be recorded without taking
> the number of threads to use into account?
> The problem is that after calculating the net desired plab size, we
> clip it to min/max sizes. This means that, when handing out the
> PLAB sizes depending on the number of threads, if the number of
> is really large, the PLAB sizes get way too small.
> I have seen some application logs where due to high number of
> around 90%(!) of multiple GB of allocations during GC is direct
> -allocated. Instead of using PLABs...
> This change fixes this issue.
> jprt, vm.gc, looking at several benchmarks to see whether the problem
> still occurs
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