Messages in this thread | | | From | Saravana Kannan <> | Date | Tue, 15 Nov 2022 14:35:51 -0800 | Subject | Re: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov_policy" |
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On Thu, Nov 10, 2022 at 11:57 AM Sam Wu <wusamuel@google.com> wrote: > > This reverts commit 6d5afdc97ea71958287364a1f1d07e59ef151b11. > > On a Pixel 6 device, it is observed that this commit increases > latency by approximately 50ms, or 20%, in migrating a task > that requires full CPU utilization from a LITTLE CPU to Fmax > on a big CPU. Reverting this change restores the latency back > to its original baseline value. > > Fixes: 6d5afdc97ea7 ("cpufreq: schedutil: Move max CPU capacity to sugov_policy") > Cc: Lukasz Luba <lukasz.luba@arm.com> > Cc: Saravana Kannan <saravanak@google.com> > Cc: Isaac J. Manjarres <isaacmanjarres@google.com> > Signed-off-by: Sam Wu <wusamuel@google.com>
Rafael, can we pick this up please?
Lukasz, no objections to the idea itself, but it's causing regression and we'd like to revert and then fix it.
-Saravana
> --- > kernel/sched/cpufreq_schedutil.c | 30 +++++++++++++++--------------- > 1 file changed, 15 insertions(+), 15 deletions(-) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 9161d1136d01..1207c78f85c1 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -25,9 +25,6 @@ struct sugov_policy { > unsigned int next_freq; > unsigned int cached_raw_freq; > > - /* max CPU capacity, which is equal for all CPUs in freq. domain */ > - unsigned long max; > - > /* The next fields are only needed if fast switch cannot be used: */ > struct irq_work irq_work; > struct kthread_work work; > @@ -51,6 +48,7 @@ struct sugov_cpu { > > unsigned long util; > unsigned long bw_dl; > + unsigned long max; > > /* The field below is for single-CPU policies only: */ > #ifdef CONFIG_NO_HZ_COMMON > @@ -160,6 +158,7 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu) > { > struct rq *rq = cpu_rq(sg_cpu->cpu); > > + sg_cpu->max = arch_scale_cpu_capacity(sg_cpu->cpu); > sg_cpu->bw_dl = cpu_bw_dl(rq); > sg_cpu->util = effective_cpu_util(sg_cpu->cpu, cpu_util_cfs(sg_cpu->cpu), > FREQUENCY_UTIL, NULL); > @@ -254,7 +253,6 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time, > */ > static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time) > { > - struct sugov_policy *sg_policy = sg_cpu->sg_policy; > unsigned long boost; > > /* No boost currently required */ > @@ -282,8 +280,7 @@ static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time) > * sg_cpu->util is already in capacity scale; convert iowait_boost > * into the same scale so we can compare. > */ > - boost = sg_cpu->iowait_boost * sg_policy->max; > - boost >>= SCHED_CAPACITY_SHIFT; > + boost = (sg_cpu->iowait_boost * sg_cpu->max) >> SCHED_CAPACITY_SHIFT; > boost = uclamp_rq_util_with(cpu_rq(sg_cpu->cpu), boost, NULL); > if (sg_cpu->util < boost) > sg_cpu->util = boost; > @@ -340,7 +337,7 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time, > if (!sugov_update_single_common(sg_cpu, time, flags)) > return; > > - next_f = get_next_freq(sg_policy, sg_cpu->util, sg_policy->max); > + next_f = get_next_freq(sg_policy, sg_cpu->util, sg_cpu->max); > /* > * Do not reduce the frequency if the CPU has not been idle > * recently, as the reduction is likely to be premature then. > @@ -376,7 +373,6 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time, > unsigned int flags) > { > struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util); > - struct sugov_policy *sg_policy = sg_cpu->sg_policy; > unsigned long prev_util = sg_cpu->util; > > /* > @@ -403,8 +399,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time, > sg_cpu->util = prev_util; > > cpufreq_driver_adjust_perf(sg_cpu->cpu, map_util_perf(sg_cpu->bw_dl), > - map_util_perf(sg_cpu->util), > - sg_policy->max); > + map_util_perf(sg_cpu->util), sg_cpu->max); > > sg_cpu->sg_policy->last_freq_update_time = time; > } > @@ -413,19 +408,25 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time) > { > struct sugov_policy *sg_policy = sg_cpu->sg_policy; > struct cpufreq_policy *policy = sg_policy->policy; > - unsigned long util = 0; > + unsigned long util = 0, max = 1; > unsigned int j; > > for_each_cpu(j, policy->cpus) { > struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j); > + unsigned long j_util, j_max; > > sugov_get_util(j_sg_cpu); > sugov_iowait_apply(j_sg_cpu, time); > + j_util = j_sg_cpu->util; > + j_max = j_sg_cpu->max; > > - util = max(j_sg_cpu->util, util); > + if (j_util * max > j_max * util) { > + util = j_util; > + max = j_max; > + } > } > > - return get_next_freq(sg_policy, util, sg_policy->max); > + return get_next_freq(sg_policy, util, max); > } > > static void > @@ -751,7 +752,7 @@ static int sugov_start(struct cpufreq_policy *policy) > { > struct sugov_policy *sg_policy = policy->governor_data; > void (*uu)(struct update_util_data *data, u64 time, unsigned int flags); > - unsigned int cpu = cpumask_first(policy->cpus); > + unsigned int cpu; > > sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC; > sg_policy->last_freq_update_time = 0; > @@ -759,7 +760,6 @@ static int sugov_start(struct cpufreq_policy *policy) > sg_policy->work_in_progress = false; > sg_policy->limits_changed = false; > sg_policy->cached_raw_freq = 0; > - sg_policy->max = arch_scale_cpu_capacity(cpu); > > sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS); > > -- > 2.38.1.431.g37b22c650d-goog >
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