linux-kernel - Re: [PATCH 3/3] sched/fair: Ensure select housekeeping cpus in task_numa_find

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Message-ID: <ea776560-2d80-40e6-b788-9d67fad20add@bytedance.com>
Date: Mon, 23 Dec 2024 20:58:07 +0800
From: Chuyi Zhou <zhouchuyi@...edance.com>
To: K Prateek Nayak <kprateek.nayak@....com>, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, vschneid@...hat.com
Cc: chengming.zhou@...ux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] sched/fair: Ensure select housekeeping cpus in
 task_numa_find_cpu



在 2024/12/18 14:21, K Prateek Nayak 写道:
> Hello Chuyi,
> 
> On 12/16/2024 5:53 PM, Chuyi Zhou wrote:
>> [..snip..]
>> @@ -2081,6 +2081,12 @@ numa_type numa_classify(unsigned int 
>> imbalance_pct,
>>       return node_fully_busy;
>>   }
>> +static inline bool numa_migrate_test_cpu(struct task_struct *p, int cpu)
>> +{
>> +    return cpumask_test_cpu(cpu, p->cpus_ptr) &&
>> +            housekeeping_cpu(cpu, HK_TYPE_DOMAIN);
>> +}
>> +
>>   #ifdef CONFIG_SCHED_SMT
>>   /* Forward declarations of select_idle_sibling helpers */
>>   static inline bool test_idle_cores(int cpu);
>> @@ -2168,7 +2174,7 @@ static void task_numa_assign(struct 
>> task_numa_env *env,
>>           /* Find alternative idle CPU. */
>>           for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start 
>> + 1) {
> 
> Can we just do:
> 
>      for_each_cpu_and(cpu, cpumask_of_node(env->dst_nid), 
> housekeeping_cpumask(HK_TYPE_DOMAIN)) {
>          ...
>      }
> 
> and avoid adding numa_migrate_test_cpu(). Thoughts?

Make sense, but now there doesn't seem to be an API like 
for_each_cpu_wrap_and().

Do you think the following is better?

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 855df103f4dd..4792ef672738 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2167,9 +2167,9 @@ static void task_numa_assign(struct task_numa_env 
*env,
                 int start = env->dst_cpu;

                 /* Find alternative idle CPU. */
-               for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), 
start + 1) {
+               for_each_cpu_and(cpu, cpumask_of_node(env->dst_nid), 
housekeeping_cpumask(HK_TYPE_DOMAIN)) {
                         if (cpu == env->best_cpu || !idle_cpu(cpu) ||
-                           !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
+                               cpu == start || !cpumask_test_cpu(cpu, 
env->p->cpus_ptr)) {
                                 continue;
                         }


Thanks.


> 
>>               if (cpu == env->best_cpu || !idle_cpu(cpu) ||
>> -                !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
>> +                !numa_migrate_test_cpu(env->p, cpu)) {
>>                   continue;
>>               }
>> @@ -2480,7 +2486,7 @@ static void task_numa_find_cpu(struct 
>> task_numa_env *env,
>>       for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
> 
> Same modifications can be made for this outer loop.
>