RFR (XS): 8150952: Net PLAB size is clipped to max PLAB size as a whole, not on a per thread basis (original) (raw)
Thomas Schatzl thomas.schatzl at oracle.com
Thu Mar 10 13:16:36 UTC 2016
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Hi all,
could I have a "R"eviewer review for this change?
Thanks, Thomas
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 desired PLAB sizes depending on the number of threads, if the number of threads is really large, the PLAB sizes get way too small. I have seen some application logs where due to high number of threads, around 90%(!) of multiple GB of allocations during GC is direct -allocated. Instead of using PLABs... This change fixes this issue. CR: https://bugs.openjdk.java.net/browse/JDK-8150952 Webrev: cr.openjdk.java.net/~tschatzl/8150952/webrev Testing: jprt, vm.gc, looking at several benchmarks to see whether the problem still occurs Thanks, Thomas
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