Messages in this thread Patch in this message | | | Date | Wed, 30 Nov 2022 14:04:36 +0000 | Subject | Re: [PATCH v1] Revert "cpufreq: schedutil: Move max CPU capacity to sugov_policy" | From | Lukasz Luba <> |
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Hi Vincent,
On 11/30/22 10:42, Vincent Guittot wrote: > Hi All > > Just for the log and because it took me a while to figure out the root > cause of the problem: This patch also creates a regression for > snapdragon845 based systems and probably on any QC chipsets that use a > LUT to update the OPP table at boot. The behavior is the same as > described by Sam with a staled value in sugov_policy.max field.
Thanks for sharing this info and apologies that you spent cycles on it.
I have checked that whole setup code (capacity + cpufreq policy and governor). It looks like to have a proper capacity of CPUs, we need to wait till the last policy is created. It's due to the arch_topology.c mechanism which is only triggered after all CPUs' got the policy. Unfortunately, this leads to a chicken & egg situation for this schedutil setup of max capacity.
I have experimented with this code, which triggers an update in the schedutil, when all CPUs got the policy and sugov gov (with trace_printk() to mach the output below)
-------------------------8<----------------------------------------- diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 9161d1136d01..f1913a857218 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -59,6 +59,7 @@ struct sugov_cpu { };
static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu); +static cpumask_var_t cpus_to_visit;
/************************ Governor internals ***********************/
@@ -783,6 +784,22 @@ static int sugov_start(struct cpufreq_policy *policy)
cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, uu); } + + cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus); + + if (cpumask_empty(cpus_to_visit)) { + trace_printk("schedutil the visit cpu mask is empty now\n"); + for_each_possible_cpu(cpu) { + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); + struct sugov_policy *sg_policy = sg_cpu->sg_policy; + + sg_policy->max = arch_scale_cpu_capacity(cpu); + + trace_printk("SCHEDUTIL: NEW CPU%u cpu_capacity=%lu\n", + cpu, sg_policy->max); + } + } + return 0; }
@@ -800,6 +817,8 @@ static void sugov_stop(struct cpufreq_policy *policy) irq_work_sync(&sg_policy->irq_work); kthread_cancel_work_sync(&sg_policy->work); } + + cpumask_or(cpus_to_visit, cpus_to_visit, policy->related_cpus); }
static void sugov_limits(struct cpufreq_policy *policy) @@ -829,6 +848,11 @@ struct cpufreq_governor schedutil_gov = { #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL struct cpufreq_governor *cpufreq_default_governor(void) { + if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) + return NULL; + + cpumask_copy(cpus_to_visit, cpu_possible_mask); + return &schedutil_gov; } #endif ---------------------------------->8---------------------------------
That simple approach fixes the issue. I have also tested it with governor change a few times and setting back the schedutil.
------------------------------------------- kworker/u12:1-48 [004] ..... 2.208847: sugov_start: schedutil the visit cpu mask is empty now kworker/u12:1-48 [004] ..... 2.208854: sugov_start: SCHEDUTIL: NEW CPU0 cpu_capacity=381 kworker/u12:1-48 [004] ..... 2.208857: sugov_start: SCHEDUTIL: NEW CPU1 cpu_capacity=381 kworker/u12:1-48 [004] ..... 2.208860: sugov_start: SCHEDUTIL: NEW CPU2 cpu_capacity=381 kworker/u12:1-48 [004] ..... 2.208862: sugov_start: SCHEDUTIL: NEW CPU3 cpu_capacity=381 kworker/u12:1-48 [004] ..... 2.208864: sugov_start: SCHEDUTIL: NEW CPU4 cpu_capacity=1024 kworker/u12:1-48 [004] ..... 2.208866: sugov_start: SCHEDUTIL: NEW CPU5 cpu_capacity=1024 bash-615 [005] ..... 35.317113: sugov_start: schedutil the visit cpu mask is empty now bash-615 [005] ..... 35.317120: sugov_start: SCHEDUTIL: NEW CPU0 cpu_capacity=381 bash-615 [005] ..... 35.317123: sugov_start: SCHEDUTIL: NEW CPU1 cpu_capacity=381 bash-615 [005] ..... 35.317125: sugov_start: SCHEDUTIL: NEW CPU2 cpu_capacity=381 bash-615 [005] ..... 35.317127: sugov_start: SCHEDUTIL: NEW CPU3 cpu_capacity=381 bash-615 [005] ..... 35.317129: sugov_start: SCHEDUTIL: NEW CPU4 cpu_capacity=1024 bash-615 [005] ..... 35.317131: sugov_start: SCHEDUTIL: NEW CPU5 cpu_capacity=1024 bash-623 [003] ..... 57.633328: sugov_start: schedutil the visit cpu mask is empty now bash-623 [003] ..... 57.633336: sugov_start: SCHEDUTIL: NEW CPU0 cpu_capacity=381 bash-623 [003] ..... 57.633339: sugov_start: SCHEDUTIL: NEW CPU1 cpu_capacity=381 bash-623 [003] ..... 57.633340: sugov_start: SCHEDUTIL: NEW CPU2 cpu_capacity=381 bash-623 [003] ..... 57.633342: sugov_start: SCHEDUTIL: NEW CPU3 cpu_capacity=381 bash-623 [003] ..... 57.633343: sugov_start: SCHEDUTIL: NEW CPU4 cpu_capacity=1024 bash-623 [003] ..... 57.633344: sugov_start: SCHEDUTIL: NEW CPU5 cpu_capacity=1024 ---------------------------------------------------- It should work.
Regards, Lukasz
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