Messages in this thread | | | Date | Wed, 18 Nov 2020 14:49:52 +0100 | From | Jan Kara <> | Subject | Re: [mm/gup] 47e29d32af: phoronix-test-suite.npb.FT.A.total_mop_s -45.0% regression |
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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... The NPB benchmark appears to be a supercomputing benchmark so concievably it could be heavily using THPs. The question is why it would be a heavy user of pinning as well but even that is imaginable considering that MPI is in use etc.
So maybe it is worth trying to reproduce this because heavy THP + pinning users might be indeed rare and only those would show regressions in THP pinning performance...
Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
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