On Fri, 6 Nov 2020 at 13:03, Mel Gorman <[email protected]> wrote: > > On Wed, Nov 04, 2020 at 09:42:05AM +0000, Mel Gorman wrote: > > While it's possible that some other factor masked the impact of the patch, > > the fact it's neutral for two workloads in 5.10-rc2 is suspicious as it > > indicates that if the patch was implemented against 5.10-rc2, it would > > likely not have been merged. I've queued the tests on the remaining > > machines to see if something more conclusive falls out. > > > > It's not as conclusive as I would like. fork_test generally benefits > across the board but I do not put much weight in that. > > Otherwise, it's workload and machine-specific. > > schbench: (wakeup latency sensitive), all machines benefitted from the > revert at the low utilisation except one 2-socket haswell machine > which showed higher variability when the machine was fully > utilised.
There is a pending patch to should improve this bench: https://lore.kernel.org/patchwork/patch/1330614/ > > hackbench: Neutral except for the same 2-socket Haswell machine which > took an 8% performance penalty of 8% for smaller number of groups > and 4% for higher number of groups. > > pipetest: Mostly neutral except for the *same* machine showing an 18% > performance gain by reverting. > > kernbench: Shows small gains at low job counts across the board -- 0.84% > lowest gain up to 5.93% depending on the machine > > gitsource: low utilisation execution of the git test suite. This was > mostly a win for the revert. For the list of machines tested it was > > 14.48% gain (2 socket but SNC enabled to 4 NUMA nodes) > neutral (2 socket broadwell) > 36.37% gain (1 socket skylake machine) > 3.18% gain (2 socket broadwell) > 4.4% (2 socket EPYC 2) > 1.85% gain (2 socket EPYC 1) > > While it was clear-cut for 5.9, it's less clear-cut for 5.10-rc2 although > the gitsource shows some severe differences depending on the machine that > is worth being extremely cautious about. I would still prefer a revert > but I'm also extremely biased and I know there are other patches in the This one from Julia can also impact > pipeline that may change the picture. A wider battery of tests might > paint a clearer picture but may not be worth the time investment. hackbench and pipetest are those that i usually run and where not facing regression it was either neutral or small gain which seems aligned with the fact that there is no much fork/exec involved in these bench My machine has faced some connections issues the last couple of days so I don't have all results; And especially the git source and kernbench one > > So maybe lets just keep an eye on this one. When the scheduler pipeline > dies down a bit (does that happen?), we should at least revisit it. > > -- > Mel Gorman > SUSE Labs
