Re: [PATCH V2 5/5] memcg: change the target nr_to_reclaim for each memcg under kswapd

[Hillf Danton <dhillf@gmail.com>]

On Thu, Apr 12, 2012 at 6:00 AM, Ying Han <yinghan@google.com> wrote:
> Under global background reclaim, the sc->nr_to_reclaim is set to
> ULONG_MAX. Now we are iterating all memcgs under the zone and we
> shouldn't pass the pressure from kswapd for each memcg.
>
> After all, the balance_pgdat() breaks after reclaiming SWAP_CLUSTER_MAX
> pages to prevent building up reclaim priorities.
>
> Signed-off-by: Ying Han <yinghan@google.com>
> ---
>  mm/vmscan.c |   12 ++++++++++--
>  1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d65eae4..ca70ec6 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2083,9 +2083,18 @@ static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
>        unsigned long nr_to_scan;
>        enum lru_list lru;
>        unsigned long nr_reclaimed, nr_scanned;
> -       unsigned long nr_to_reclaim = sc->nr_to_reclaim;
> +       unsigned long nr_to_reclaim;
>        struct blk_plug plug;
>
> +       /*
> +        * Under global background reclaim, the sc->nr_to_reclaim is set to
> +        * ULONG_MAX. Now we are iterating all memcgs under the zone and we
> +        * shouldn't pass the pressure from kswapd for each memcg. After all,
> +        * the balance_pgdat() breaks after reclaiming SWAP_CLUSTER_MAX pages
> +        * to prevent building up reclaim priorities.
> +        */
> +       nr_to_reclaim = min_t(unsigned long,
> +                             sc->nr_to_reclaim, SWAP_CLUSTER_MAX);
>  restart:
>        nr_reclaimed = 0;
>        nr_scanned = sc->nr_scanned;
>
Since priority is one of the factors used in computing scan count, we could
change how to select a memcg for reclaim,

	return target_mem_cgroup ||
		mem_cgroup_soft_limit_exceeded(memcg) ||
		priority != DEF_PRIORITY;

where detection of all mem groups under softlimit happens at DEF_PRIORITY-1.

Then selected mem groups are reclaimed in the current manner without change
in nr_to_reclaim, and sc->nr_reclaimed is distributed evenly among mem groups,
no matter softlimt is exceeded or not.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>