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")
Signed-off-by: Sam Wu <wusamuel@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 9161d11..1207c78 100644 (file)
--- 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);