Re: [RFC PATCH 0/3] Do not wait the full timeout on congestion_wait when there is no congestion

[Wu Fengguang <fengguang.wu@intel.com>]

Minchan,

It's much cleaner to keep the unchanged congestion_wait() and add a
congestion_wait_check() for converting problematic wait sites. The
too_many_isolated() wait is merely a protective mechanism, I won't
bother to improve it at the cost of more code.

Thanks,
Fengguang

> diff --git a/mm/compaction.c b/mm/compaction.c
> index 94cce51..7370683 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -253,7 +253,11 @@ static unsigned long isolate_migratepages(struct zone *zone,
>          * delay for some time until fewer pages are isolated
>          */  
>         while (unlikely(too_many_isolated(zone))) {
> -               congestion_wait(BLK_RW_ASYNC, HZ/10);
> +               long timeout = HZ/10;
> +               if (timeout == congestion_wait(BLK_RW_ASYNC, timeout)) {
> +                       set_current_state(TASK_INTERRUPTIBLE);
> +                       schedule_timeout(timeout);
> +               }
> 
>                 if (fatal_signal_pending(current))
>                         return 0;

> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3109ff7..f5e3e28 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1337,7 +1337,11 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>         unsigned long nr_dirty;
>         while (unlikely(too_many_isolated(zone, file, sc))) {
> -               congestion_wait(BLK_RW_ASYNC, HZ/10);
> +               long timeout = HZ/10;
> +               if (timeout == congestion_wait(BLK_RW_ASYNC, timeout)) {
> +                       set_current_state(TASK_INTERRUPTIBLE);
> +                       schedule_timeout(timeout);
> +               }
> 
>                 /* We are about to die and free our memory. Return now. */
>                 if (fatal_signal_pending(current))
> -- 
> 1.7.0.5
> 
> 
> -- 
> Kind regards,
> Minchan Kim