On Wed, Feb 23, 2022 at 07:30:52PM +0800, Aaron Lu wrote: > On Mon, Feb 21, 2022 at 09:38:22PM +0800, Aaron Lu wrote: > > On Fri, Feb 18, 2022 at 12:20:03PM +0800, Aaron Lu wrote: > > > On Thu, Feb 17, 2022 at 09:31:13AM +0000, Mel Gorman wrote: > > > > On Thu, Feb 17, 2022 at 09:53:08AM +0800, Aaron Lu wrote: > > > > > > 2-socket CascadeLake (40 cores, 80 CPUs HT enabled) > > > > > > 5.17.0-rc3 5.17.0-rc3 > > > > > > vanilla mm-highpcpopt-v2 > > > > > > Hmean page_fault1-processes-2 2694662.26 ( 0.00%) 2695780.35 ( 0.04%) > > > > > > Hmean page_fault1-processes-5 6425819.34 ( 0.00%) 6435544.57 * 0.15%* > > > > > > Hmean page_fault1-processes-8 9642169.10 ( 0.00%) 9658962.39 ( 0.17%) > > > > > > Hmean page_fault1-processes-12 12167502.10 ( 0.00%) 12190163.79 ( 0.19%) > > > > > > Hmean page_fault1-processes-21 15636859.03 ( 0.00%) 15612447.26 ( -0.16%) > > > > > > Hmean page_fault1-processes-30 25157348.61 ( 0.00%) 25169456.65 ( 0.05%) > > > > > > Hmean page_fault1-processes-48 27694013.85 ( 0.00%) 27671111.46 ( -0.08%) > > > > > > Hmean page_fault1-processes-79 25928742.64 ( 0.00%) 25934202.02 ( 0.02%) <-- > > > > > > Hmean page_fault1-processes-110 25730869.75 ( 0.00%) 25671880.65 * -0.23%* > > > > > > Hmean page_fault1-processes-141 25626992.42 ( 0.00%) 25629551.61 ( 0.01%) > > > > > > Hmean page_fault1-processes-172 25611651.35 ( 0.00%) 25614927.99 ( 0.01%) > > > > > > Hmean page_fault1-processes-203 25577298.75 ( 0.00%) 25583445.59 ( 0.02%) > > > > > > Hmean page_fault1-processes-234 25580686.07 ( 0.00%) 25608240.71 ( 0.11%) > > > > > > Hmean page_fault1-processes-265 25570215.47 ( 0.00%) 25568647.58 ( -0.01%) > > > > > > Hmean page_fault1-processes-296 25549488.62 ( 0.00%) 25543935.00 ( -0.02%) > > > > > > Hmean page_fault1-processes-320 25555149.05 ( 0.00%) 25575696.74 ( 0.08%) > > > > > > > > > > > > The differences are mostly within the noise and the difference close to > > > > > > $nr_cpus is negligible. > > > > > > > > > > I have queued will-it-scale/page_fault1/processes/$nr_cpu on 2 4-sockets > > > > > servers: CascadeLake and CooperLaker and will let you know the result > > > > > once it's out. > > > > > > > > > > > > > Thanks, 4 sockets and a later generation would be nice to cover. > > > > > > > > > I'm using 'https://github.com/hnaz/linux-mm master' and doing the > > > > > comparison with commit c000d687ce22("mm/page_alloc: simplify how many > > > > > pages are selected per pcp list during bulk free") and commit 8391e0a7e172 > > > > > ("mm/page_alloc: free pages in a single pass during bulk free") there. > > > > > > > > > > > > > The baseline looks fine. It's different to what I used but the page_alloc > > > > shouldn't have much impact. > > > > > > > > When looking at will-it-scale, please pay attention to lower CPU counts > > > > as well and take account changes in standard deviation. Looking at the > > > > > > I'll also test nr_task=4/16/64 on the 4sockets CooperLake(nr_cpu=144) then. > > > > > > > For the record, these tests don't show any visible performance changes > > on CooperLake. > > One thing I just noticed is that, zone lock contention increased to some > extent. I'm not sure if this is worrisome so I suppose I should at least > mention it here. > > The nr_task=100% test on the 4 sockets Cooper Lake showed that zone lock > contention increased from 13.56% to 20.16% and for nr_task=16, it > increased from 4.75% to 6.18%. > > The reason is probably due to more code are now inside the lock and when > there is contention, it will make things worse. I'm aware of that > nr_task=100% is a rare case and this patchset is meant to improve things > when there is very little contention, which should be the common case. > So I guess that's just the tradeoff we have to make... > I think it's a reasonable tradeoff. The page_fault1 will-it-scale is an extreme case that exercises severe contention for the zone lock with both allocators and freeing contending for the lock at the same time. I think it's reasonable to optimise for the common case of completing the bulk freeing as quickly as possible. If anything, I think will-it-scale would benefit more if zone->lock was split to cover regions within a zone instead of protecting an entire zone which could be hundreds of GB in size. -- Mel Gorman SUSE Labs
