Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [RFC PATCH 6/6] cpuset: Add cpuset.isolation_mask file | Date | Thu, 15 Jul 2021 00:44:08 +0100 |
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On 15/07/21 01:13, Frederic Weisbecker wrote: > On Wed, Jul 14, 2021 at 06:52:43PM +0200, Peter Zijlstra wrote: >> >> cpusets already has means to create paritions; why are you creating >> something else? > > I was about to answer that the semantics of isolcpus, which reference > a NULL domain, are different from SD_LOAD_BALANCE implied by > cpuset.sched_load_balance. But then I realize that SD_LOAD_BALANCE has > been removed. > > How cpuset.sched_load_balance is implemented then? Commit > e669ac8ab952df2f07dee1e1efbf40647d6de332 ("sched: Remove checks against > SD_LOAD_BALANCE") advertize that setting cpuset.sched_load_balance to 0 > ends up creating NULL domain but that's not what I get. For example if I > mount a single cpuset root (no other cpuset mountpoints): > > $ mount -t cgroup none ./cpuset -o cpuset > $ cd cpuset > $ cat cpuset.cpus > 0-7 > $ cat cpuset.sched_load_balance > 1 > $ echo 0 > cpuset.sched_load_balance > $ ls /sys/kernel/debug/domains/cpu1/ > domain0 domain1 > > I still get the domains on all CPUs...
Huh. That's on v5.14-rc1 with an automounted cpuset:
$ cat /sys/fs/cgroup/cpuset/cpuset.cpus 0-5 $ cat /sys/fs/cgroup/cpuset/cpuset.sched_load_balance 1
$ ls /sys/kernel/debug/sched/domains/cpu* /sys/kernel/debug/sched/domains/cpu0: domain0 domain1
/sys/kernel/debug/sched/domains/cpu1: domain0 domain1
/sys/kernel/debug/sched/domains/cpu2: domain0 domain1
/sys/kernel/debug/sched/domains/cpu3: domain0 domain1
/sys/kernel/debug/sched/domains/cpu4: domain0 domain1
/sys/kernel/debug/sched/domains/cpu5: domain0 domain1
$ echo 0 > /sys/fs/cgroup/cpuset/cpuset.sched_load_balance $ ls /sys/kernel/debug/sched/domains/cpu* /sys/kernel/debug/sched/domains/cpu0:
/sys/kernel/debug/sched/domains/cpu1:
/sys/kernel/debug/sched/domains/cpu2:
/sys/kernel/debug/sched/domains/cpu3:
/sys/kernel/debug/sched/domains/cpu4:
/sys/kernel/debug/sched/domains/cpu5:
I also checked that you can keep cpuset.sched_load_balance=0 at the root and create exclusive child cpusets with different values of sched_load_balance, giving you some CPUs attached to the NULL domain and some others with a sched_domain hierarchy that stays within the cpuset span.
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