Commit 7fb3ff22 authored by Yair Podemsky's avatar Yair Podemsky Committed by Ingo Molnar

sched/core: Fix arch_scale_freq_tick() on tickless systems

In order for the scheduler to be frequency invariant we measure the
ratio between the maximum CPU frequency and the actual CPU frequency.

During long tickless periods of time the calculations that keep track
of that might overflow, in the function scale_freq_tick():

  if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt))
          goto error;

eventually forcing the kernel to disable the feature for all CPUs,
and show the warning message:

   "Scheduler frequency invariance went wobbly, disabling!".

Let's avoid that by limiting the frequency invariant calculations
to CPUs with regular tick.

Fixes: e2b0d619 ("x86, sched: check for counters overflow in frequency invariant accounting")
Suggested-by: default avatar"Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: default avatarYair Podemsky <ypodemsk@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarValentin Schneider <vschneid@redhat.com>
Acked-by: default avatarGiovanni Gherdovich <ggherdovich@suse.cz>
Link: https://lore.kernel.org/r/20221130125121.34407-1-ypodemsk@redhat.com
parent 0a715535
......@@ -5504,7 +5504,9 @@ void scheduler_tick(void)
unsigned long thermal_pressure;
u64 resched_latency;
if (housekeeping_cpu(cpu, HK_TYPE_TICK))
arch_scale_freq_tick();
sched_clock_tick();
rq_lock(rq, &rf);
......
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