[GIT PULL] scheduler fixes

Ingo Molnar
2024-01-11T11:09:28Z

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Wed, 10 Jan 2024 at 14:41, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > It's one of these two:
> >
> > f12560779f9d sched/cpufreq: Rework iowait boost
> > 9c0b4bb7f630 sched/cpufreq: Rework schedutil governor performance estimation
> >
> > one more boot to go, then I'll try to revert whichever causes my
> > machine to perform horribly much worse.
>
> I guess it should come as no surprise that the result is
>
> 9c0b4bb7f6303c9c4e2e34984c46f5a86478f84d is the first bad commit
>
> but to revert cleanly I will have to revert all of
>
> b3edde44e5d4 ("cpufreq/schedutil: Use a fixed reference frequency")
> f12560779f9d ("sched/cpufreq: Rework iowait boost")
> 9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor
> performance estimation")
>
> This is on a 32-core (64-thread) AMD Ryzen Threadripper 3970X, fwiw.
>
> I'll keep that revert in my private test-tree for now (so that I have
> a working machine again), but I'll move it to my main branch soon
> unless somebody has a quick fix for this problem.

Thanks a lot for bisecting this, and ack on the revert in any case, these
are relatively fresh changes that clearly didn't get enough testing - sorry!

I also made the revert in sched/urgent & added a changelog, which you can
pull from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2024-01-11

# HEAD: 250ce3c1169743f3575cc5937fccd72380052795 Revert "sched/cpufreq: Rework schedutil governor performance estimation" and dependent commits

Revert recent changes to the sched_util logic, to address a bad
performance regression that increased kernel build time on Linus's
64-CPU desktop system substantially.

Lightly build and boot tested.

Thanks,

Ingo

------------------>
Ingo Molnar (1):
Revert "sched/cpufreq: Rework schedutil governor performance estimation" and dependent commits

include/linux/energy_model.h | 1 +
kernel/sched/core.c | 90 +++++++++++++++++++++++-----------------
kernel/sched/cpufreq_schedutil.c | 90 ++++++++++++----------------------------
kernel/sched/fair.c | 22 ++--------
kernel/sched/sched.h | 84 +++++++++++++++++++++++++++++++++----
5 files changed, 160 insertions(+), 127 deletions(-)