Messages in this thread |  | | Date | Wed, 21 May 2025 15:59:29 +0200 | | Subject | Re: scheduler performance regression since v6.11 | | From | Dietmar Eggemann <> |
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On 20/05/2025 16:53, Chris Mason wrote: > On 5/20/25 10:38 AM, Dietmar Eggemann wrote: >> On 16/05/2025 12:18, Peter Zijlstra wrote: >>> On Mon, May 12, 2025 at 06:35:24PM -0400, Chris Mason wrote:
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>> I can't spot any v6.11 related changes (dl_server or TTWU_QUEUE) but a >> PSI related one for v6.12 results in a ~8% schbench regression. >> >> VM (m7gd.16xlarge, 16 logical CPUs) on Graviton3: >> >> schbench -L -m 4 -M auto -t 128 -n 0 -r 60 >> >> 3840cbe24cf0 - sched: psi: fix bogus pressure spikes from aggregation race > > I also saw a regression on this one, but it wasn't stable enough for me > to be sure. I'll retest, but I'm guessing this is made worse by the VM > / graviton setup?
For me the 8% regression here is pretty stable. I have to add that I ran schbench in:
/sys/fs/cgroup/user.slice/user-1000.slice/session-33.scope
So that explains IMHO the 4 calls to psi_group_change() from psi_task_switch() now doing all their own 'now = cpu_clock(cpu)' call.
schbench-6509 [004] d.... 689.050466: psi_task_switch: CPU4 [schbench 6509] -> [schbench 6514] -> schbench-6509 [004] d.... 689.050466: psi_group_change: CPU4 now=689050466118 schbench-6509 [004] d.... 689.050467: psi_group_change: CPU4 now=689050466537 schbench-6509 [004] d.... 689.050467: psi_group_change: CPU4 now=689050466950 schbench-6509 [004] d.... 689.050468: psi_group_change: CPU4 now=689050467838 schbench-6509 [004] d.... 689.050468: psi_task_switch: CPU4 [schbench 6509] -> [schbench 6514] <- > I've been testing Peter's changes, and they do help on my skylake box > but not as much on the big turin machines. I'm trying to sort that out,
Turin vs. SKL,SPR ?
> but we have some other variables wrt PGO/LTO that I need to rule out.
OK, thanks! We also started testing this on Arm64 server with +20 cores ...
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