From 8ecf04e11283a28ca88b8b8049ac93c3a99fcd2c Mon Sep 17 00:00:00 2001 From: Patrick Bellasi Date: Thu, 24 May 2018 15:10:22 +0100 Subject: sched/cpufreq: Modify aggregate utilization to always include blocked FAIR utilization Since the refactoring introduced by: commit 8f111bc357aa ("cpufreq/schedutil: Rewrite CPUFREQ_RT support") we aggregate FAIR utilization only if this class has runnable tasks. This was mainly due to avoid the risk to stay on an high frequency just because of the blocked utilization of a CPU not being properly decayed while the CPU was idle. However, since: commit 31e77c93e432 ("sched/fair: Update blocked load when newly idle") the FAIR blocked utilization is properly decayed also for IDLE CPUs. This allows us to use the FAIR blocked utilization as a safe mechanism to gracefully reduce the frequency only if no FAIR tasks show up on a CPU for a reasonable period of time. Moreover, we also reduce the frequency drops of CPUs running periodic tasks which, depending on the task periodicity and the time required for a frequency switch, was increasing the chances to introduce some undesirable performance variations. Reported-by: Vincent Guittot Tested-by: Vincent Guittot Signed-off-by: Patrick Bellasi Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Acked-by: Viresh Kumar Acked-by: Vincent Guittot Cc: Dietmar Eggemann Cc: Joel Fernandes Cc: Juri Lelli Cc: Linus Torvalds Cc: Morten Rasmussen Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Steve Muckle Link: http://lkml.kernel.org/r/20180524141023.13765-2-patrick.bellasi@arm.com Signed-off-by: Ingo Molnar --- kernel/sched/cpufreq_schedutil.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) (limited to 'kernel/sched') diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index e13df951aca7..28592b62b1d5 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -183,22 +183,21 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu) static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu) { struct rq *rq = cpu_rq(sg_cpu->cpu); - unsigned long util; - if (rq->rt.rt_nr_running) { - util = sg_cpu->max; - } else { - util = sg_cpu->util_dl; - if (rq->cfs.h_nr_running) - util += sg_cpu->util_cfs; - } + if (rq->rt.rt_nr_running) + return sg_cpu->max; /* + * Utilization required by DEADLINE must always be granted while, for + * FAIR, we use blocked utilization of IDLE CPUs as a mechanism to + * gracefully reduce the frequency when no tasks show up for longer + * periods of time. + * * Ideally we would like to set util_dl as min/guaranteed freq and * util_cfs + util_dl as requested freq. However, cpufreq is not yet * ready for such an interface. So, we only do the latter for now. */ - return min(util, sg_cpu->max); + return min(sg_cpu->max, (sg_cpu->util_dl + sg_cpu->util_cfs)); } static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time, unsigned int flags) -- cgit