[PATCH RESEND] sched/numa: expose per-task pages-migration-failure

[PATCH RESEND] sched/numa: expose per-task pages-migration-failure

[王贇]

NUMA balancing will try to migrate pages between nodes, which
could caused by memory policy or numa group aggregation, while
the page migration could failed too for eg when the target node
run out of memory.

Since this is critical to the performance, admin should know
how serious the problem is, and take actions before it causing
too much performance damage, thus this patch expose the counter
as 'migfailed' in '/proc/PID/sched'.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Koutný <mkoutny@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
---
 kernel/sched/debug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index f7e4579e746c..73c4809c8f37 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -848,6 +848,7 @@ static void sched_show_numa(struct task_struct *p, struct seq_file *m)
 	P(total_numa_faults);
 	SEQ_printf(m, "current_node=%d, numa_group_id=%d\n",
 			task_node(p), task_numa_group_id(p));
+	SEQ_printf(m, "migfailed=%lu\n", p->numa_faults_locality[2]);
 	show_numa_stats(p, m);
 	mpol_put(pol);
 #endif
-- 
2.14.4.44.g2045bb6

Re: [PATCH RESEND] sched/numa: expose per-task pages-migration-failure

[Ingo Molnar]

* 王贇 <yun.wang@linux.alibaba.com> wrote:

> NUMA balancing will try to migrate pages between nodes, which
> could caused by memory policy or numa group aggregation, while
> the page migration could failed too for eg when the target node
> run out of memory.
> 
> Since this is critical to the performance, admin should know
> how serious the problem is, and take actions before it causing
> too much performance damage, thus this patch expose the counter
> as 'migfailed' in '/proc/PID/sched'.
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Michal Koutný <mkoutny@suse.com>
> Acked-by: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
> ---
>  kernel/sched/debug.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index f7e4579e746c..73c4809c8f37 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -848,6 +848,7 @@ static void sched_show_numa(struct task_struct *p, struct seq_file *m)
>  	P(total_numa_faults);
>  	SEQ_printf(m, "current_node=%d, numa_group_id=%d\n",
>  			task_node(p), task_numa_group_id(p));
> +	SEQ_printf(m, "migfailed=%lu\n", p->numa_faults_locality[2]);

Any reason not to expose the other 2 fields of this array as well, which 
show remote/local migrations?

Thanks,

	Ingo

Re: [PATCH RESEND] sched/numa: expose per-task pages-migration-failure

[王贇]

On 2019/12/3 下午3:16, Ingo Molnar wrote:
[snip]
>>  kernel/sched/debug.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
>> index f7e4579e746c..73c4809c8f37 100644
>> --- a/kernel/sched/debug.c
>> +++ b/kernel/sched/debug.c
>> @@ -848,6 +848,7 @@ static void sched_show_numa(struct task_struct *p, struct seq_file *m)
>>  	P(total_numa_faults);
>>  	SEQ_printf(m, "current_node=%d, numa_group_id=%d\n",
>>  			task_node(p), task_numa_group_id(p));
>> +	SEQ_printf(m, "migfailed=%lu\n", p->numa_faults_locality[2]);
> 
> Any reason not to expose the other 2 fields of this array as well, which 
> show remote/local migrations?

The rest are local/remote faults counter, AFAIK not related to
migration, when the CPU triggered PF is from the same node of page
(before migration), local faults increased.

Regards,
Michael Wang

> 
> Thanks,
> 
> 	Ingo
>