From e59312ac89eb014d92e3614727b6d149f1a5ce9f Mon Sep 17 00:00:00 2001 From: Phil Auld Date: Thu, 30 Mar 2023 11:52:21 -0400 Subject: [PATCH] sched/core: Fix arch_scale_freq_tick() on tickless systems Bugzilla: https://bugzilla.redhat.com/1996625 commit 7fb3ff22ad8772bbf0e3ce1ef3eb7b09f431807f Author: Yair Podemsky Date: Wed Nov 30 14:51:21 2022 +0200 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: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting") Suggested-by: "Peter Zijlstra (Intel)" Signed-off-by: Yair Podemsky Signed-off-by: Ingo Molnar Reviewed-by: Valentin Schneider Acked-by: Giovanni Gherdovich Link: https://lore.kernel.org/r/20221130125121.34407-1-ypodemsk@redhat.com Signed-off-by: Phil Auld --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5abf3071ba4b..a9a91a8b264f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5590,7 +5590,9 @@ void scheduler_tick(void) unsigned long thermal_pressure; u64 resched_latency; - arch_scale_freq_tick(); + if (housekeeping_cpu(cpu, HK_TYPE_TICK)) + arch_scale_freq_tick(); + sched_clock_tick(); rq_lock(rq, &rf);