Messages in this thread | | | Date | Fri, 20 Nov 2020 10:42:35 +0800 | From | Oliver Sang <> | Subject | Re: [mm/gup] 47e29d32af: phoronix-test-suite.npb.FT.A.total_mop_s -45.0% regression |
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On Wed, Nov 18, 2020 at 10:17:27AM -0800, Dan Williams wrote: > On Wed, Nov 18, 2020 at 5:51 AM Jan Kara <jack@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?
- some extra phoronix test suites are enabled/fixed gradually so we will have better coverage - we scan kernel releases within the year to baseline the performance, it may trigger bisection if one release has regressed and not recovered.
With this continuous effort, 0-day ci can detect the changes on mainline.
> 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.
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