From 92b0051217f23cba7541d6c4ecbca026477fb642 Mon Sep 17 00:00:00 2001 From: Yair Podemsky Date: Wed, 30 Nov 2022 14:51:21 +0200 Subject: [PATCH] sched/core: Fix arch_scale_freq_tick() on tickless systems [ Upstream commit 7fb3ff22ad8772bbf0e3ce1ef3eb7b09f431807f ] 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: Sasha Levin --- 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 981e41c..172ec79 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5498,7 +5498,9 @@ 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); -- 2.7.4