RFR: 8210416: [linux] Poor StrictMath performance due to non-optimized compilation

Severin Gehwolf sgehwolf at redhat.com
Mon Sep 10 09:27:53 UTC 2018


On Mon, 2018-09-10 at 10:05 +0100, Andrew Haley wrote:
> On 09/05/2018 02:12 PM, Severin Gehwolf wrote:
> > Is there a good
> > reason to not use -O3 -ffp-contract=off everywhere?
> 
> Is there a good reason to use -O3 rather than -O2?

Not sure. I was following what JDK-8170153 did, which was using
OPTIMIZATION := HIGH corresponding to -O3. cc'ing Gustavo. Gustavo,
would you know why HIGH was chosen over, LOW?

> -O3 can bloat the
> code which can increase cache pressure, which is not always noticeable
> in benchmarks but hurts real-world programs. Unless benchmarks are
> significantly better at -O3, -O2 is a good default choice.

OK, thanks! I'll re-test and change to LOW (-O2) if it gives similar
results.

Thanks,
Severin



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