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Date: Thu, 10 Nov 2022 19:57:32 +0000
From: Sam Wu <wusamuel@...gle.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Lukasz Luba <lukasz.luba@....com>
Cc: Sam Wu <wusamuel@...gle.com>,
Saravana Kannan <saravanak@...gle.com>,
"Isaac J . Manjarres" <isaacmanjarres@...gle.com>,
kernel-team@...roid.com,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov_policy"
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@....com>
Cc: Saravana Kannan <saravanak@...gle.com>
Cc: Isaac J. Manjarres <isaacmanjarres@...gle.com>
Signed-off-by: Sam Wu <wusamuel@...gle.com>
---
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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