On 11/18/20 10:17 AM, Dan Williams wrote:
On Wed, Nov 18, 2020 at 5:51 AM Jan Kara <j...@suse.cz> wrote:
On Mon 16-11-20 19:35:31, John Hubbard wrote:
On 11/16/20 6:48 PM, kernel test robot wrote:
Greeting,
FYI, we noticed a -45.0% regression of phoronix-test-suite.npb.FT.A.total_mop_s
due to commit:
That's a huge slowdown...
commit: 47e29d32afba11b13efb51f03154a8cf22fb4360 ("mm/gup:
page->hpage_pinned_refcount: exact pin counts for huge pages")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
...but that commit happened in April, 2020. Surely if this were a serious
issue we would have some other indication...is this worth following up
on?? I'm inclined to ignore it, honestly.
Why this was detected so late is a fair question although it doesn't quite
invalidate the report...
I don't know what specifically happened in this case, perhaps someone
from the lkp team can comment? However, the myth / contention that
"surely someone else would have noticed by now" is why the lkp project
was launched. Kernels regressed without much complaint and it wasn't
until much later in the process, around the time enterprise distros
rebased to new kernels, did end users start filing performance loss
regression reports. Given -stable kernel releases, 6-7 months is still
faster than many end user upgrade cycles to new kernel baselines.
I see, thanks for explaining. I'll take a peek, then.
thanks,
--
John Hubbard
NVIDIA
