Re: [PATCH 2/3 v2] sched/fair: don't set LBF_ALL_PINNED unnecessarily

[Mel Gorman]

On Thu, Jan 07, 2021 at 11:33:24AM +0100, Vincent Guittot wrote:
> Setting LBF_ALL_PINNED during active load balance is only valid when there
> is only 1 running task on the rq otherwise this ends up increasing the
> balance interval whereas other tasks could migrate after the next interval
> once they become cache-cold as an example.
> 
> LBF_ALL_PINNED flag is now always set it by default. It is then cleared
> when we find one task that can be pulled when calling detach_tasks() or
> during active migration.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

When reviewing this, I found it curious that sched_nr_migrate_break is
a const instead of a #define. It's not clear why as it only appears to
exist in case sysctl_sched_nr_migrate is set higher than 32 to prevent
rq lock starvation.

With your patch, s/atleast/at least/ in the comments if there is another
version.

Otherwise, I didn't spot a real problem so

Acked-by: Mel Gorman <mgorman@xxxxxxx>

-- 
Mel Gorman
SUSE Labs