Messages in this thread | | | Subject | Re: sched: Move SCHED_DEBUG sysctl to debugfs | From | Christian Borntraeger <> | Date | Wed, 28 Apr 2021 11:31:34 +0200 |
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On 28.04.21 11:25, Peter Zijlstra wrote: > On Wed, Apr 28, 2021 at 10:54:37AM +0200, Christian Borntraeger wrote: >> >> >> On 28.04.21 10:46, Peter Zijlstra wrote: >>> On Tue, Apr 27, 2021 at 04:59:25PM +0200, Christian Borntraeger wrote: >>>> Peter, >>>> >>>> I just realized that we moved away sysctl tunabled to debugfs in next. >>>> We have seen several cases where it was benefitial to set >>>> sched_migration_cost_ns to a lower value. For example with KVM I can >>>> easily get 50% more transactions with 50000 instead of 500000. >>>> Until now it was possible to use tuned or /etc/sysctl.conf to set >>>> these things permanently. >>>> >>>> Given that some people do not want to have debugfs mounted all the time >>>> I would consider this a regression. The sysctl tunable was always >>>> available. >>>> >>>> I am ok with the "informational" things being in debugfs, but not >>>> the tunables. So how do we proceed here? >>> >>> It's all SCHED_DEBUG; IOW you're relying on DEBUG infrastructure for >>> production performance, and that's your fail. >> >> No its not. sched_migration_cost_ns was NEVER protected by CONFIG_SCHED_DEBUG. >> It was available on all kernels with CONFIG_SMP. > > The relevant section from origin/master:kernel/sysctl.c:
[...] > How is migration_cost not under SCHED_DEBUG? The bigger problem is that > world+dog has SCHED_DEBUG=y in their .config.
Hmm, yes my bad. I disabled it but it was silently reenabled due to a dependency. So yes you are right, it is under SCHED_DEBUG.
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