On Thu, Aug 6, 2020 at 6:35 AM Ingo Molnar <mingo(a)kernel.org>
> * kernel test robot <rong.a.chen(a)intel.com> wrote:
> > Greeting,
> > FYI, we noticed a -43.3% regression of fio.read_iops due to commit:
> > commit: a0ac629ebe7b3d248cb93807782a00d9142fdb98 ("x86/copy_mc: Introduce
> > url:
> > in testcase: fio-basic
> > on test machine: 96 threads Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 256G
> > with following parameters:
> So this performance regression, if it isn't a spurious result, looks
> concerning. Is this expected?
This is not expected and I think delays these patches until I'm back
from leave in a few weeks. I know that we might lose some inlining
effect due to replacing native memcpy, but I did not expect it would
have an impact like this. In my testing I was seeing a performance
improvement from replacing the careful / open-coded copy with rep;
mov;, which increases the surprise of this result.
It would be nice to double check this on the kernel-test-robot side as
well, to make sure it's not a false positive.