Messages in this thread | | | From | Odin Ugedal <> | Date | Mon, 26 Apr 2021 18:33:19 +0200 | Subject | Re: [PATCH 0/1] sched/fair: Fix unfairness caused by missing load decay |
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Hi,
> Have you been able to reproduce this on mainline ?
Yes. I have been debugging and testing with v5.12-rc8. After I found the suspected commit in ~v4.8, I compiled both the v4.4.267 and v4.9.267, and was able to successfully reproduce it on v4.9.267 and not on v4.4.267. It is also reproducible on 5.11.16-arch1-1 that my distro ships, and it is reproducible on all the machines I have tested.
> When running the script below on v5.12, I'm not able to reproduce your problem
v5.12 is pretty fresh, so I have not tested on anything before v5.12-rc8. I did compile v5.12.0 now, and I am able to reproduce it there as well.
Which version did you try (the one for cgroup v1 or v2)? And/or did you try to run the inspection bpftrace script? If you tested the cg v1 version, it will often end up at 50/50, 51/49 etc., and sometimes 60/40+-, making it hard to verify without inspection.
I have attached a version of the "sub cgroup" example for cgroup v1, that also force the process to start on cpu 1 (CPU_ME), and sends it over to cpu 0 (CPU) after attaching to the new cgroup. That will make it evident each time. This example should also always end up with 50/50 per stress process, but "always" ends up more like 99/1.
Can you confirm if you are able to reproduce with this version?
--- bash start CGROUP_CPU=/sys/fs/cgroup/cpu/slice CGROUP_CPUSET=/sys/fs/cgroup/cpuset/slice CGROUP_CPUSET_ME=/sys/fs/cgroup/cpuset/me CPU=0 CPU_ME=1
function run_sandbox { local CG_CPUSET="$1" local CG_CPU="$2" local INNER_SHARES="$3" local CMD="$4"
local PIPE="$(mktemp -u)" mkfifo "$PIPE" sh -c "read < $PIPE ; exec $CMD" & local TASK="$!" sleep .1 mkdir -p "$CG_CPUSET" mkdir -p "$CG_CPU"/sub tee "$CG_CPU"/sub/cgroup.procs <<< "$TASK" tee "$CG_CPU"/sub/cpu.shares <<< "$INNER_SHARES"
tee "$CG_CPUSET"/cgroup.procs <<< "$TASK"
tee "$PIPE" <<< sandox_done rm "$PIPE" }
mkdir -p "$CGROUP_CPU" mkdir -p "$CGROUP_CPUSET" mkdir -p "$CGROUP_CPUSET_ME"
tee "$CGROUP_CPUSET"/cpuset.cpus <<< "$CPU" tee "$CGROUP_CPUSET"/cpuset.mems <<< "$CPU"
tee "$CGROUP_CPUSET_ME"/cpuset.cpus <<< "$CPU_ME" echo $$ | tee "$CGROUP_CPUSET_ME"/cgroup.procs
run_sandbox "$CGROUP_CPUSET" "$CGROUP_CPU/cg-1" 50000 "stress --cpu 1" run_sandbox "$CGROUP_CPUSET" "$CGROUP_CPU/cg-2" 2 "stress --cpu 1"
read # click enter to cleanup and stop all stress procs killall stress sleep .2 rmdir /sys/fs/cgroup/cpuset/slice/ rmdir /sys/fs/cgroup/cpu/slice/{cg-{1,2}{/sub,},} --- bash end
Thanks Odin
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