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SubjectRe: [PATCH 2/3] sched,numa: retry placement more frequently when misplaced
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On Fri, 2014-04-11 at 13:00 -0400, riel@redhat.com wrote:
> This patch reduces the interval at which migration is retried,
> when the task's numa_scan_period is small.

More style trivia and a question.

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
[]
> @@ -1326,12 +1326,15 @@ static int task_numa_migrate(struct task_struct *p)
> /* Attempt to migrate a task to a CPU on the preferred node. */
> static void numa_migrate_preferred(struct task_struct *p)
> {
> + unsigned long interval = HZ;

Perhaps it'd be better without the unnecessary initialization.

> /* This task has no NUMA fault statistics yet */
> if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory))
> return;
>
> /* Periodically retry migrating the task to the preferred node */
> - p->numa_migrate_retry = jiffies + HZ;
> + interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);

and use

interval = min_t(unsigned long, HZ,
msecs_to_jiffies(p->numa_scan_period) / 16);


btw; why 16?

Can msecs_to_jiffies(p->numa_scan_period) ever be < 16?




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