On Thu, May 12, 2011 at 8:10 PM, KAMEZAWA Hiroyuki <
kamezawa.hiroyu@jp.fujitsu.com> wrote:

>
> ZONE_CONGESTED should be a state of global memory reclaim.
> If not, a busy memcg sets this and give unnecessary throttoling in
> wait_iff_congested() against memory recalim in other contexts. This makes
> system performance bad.
>
> I'll think about "memcg is congested!" flag is required or not, later.
> But this fix is required 1st.
>

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  mm/vmscan.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> Index: mmotm-May11/mm/vmscan.c
> ===================================================================
> --- mmotm-May11.orig/mm/vmscan.c
> +++ mmotm-May11/mm/vmscan.c
> @@ -941,7 +941,8 @@ keep_lumpy:
>         * back off and wait for congestion to clear because further reclaim
>         * will encounter the same problem
>         */
> -       if (nr_dirty == nr_congested && nr_dirty != 0)
> +       if (scanning_global_lru(sc) &&
> +           nr_dirty == nr_congested && nr_dirty != 0)
>                zone_set_flag(zone, ZONE_CONGESTED);
>
>        free_page_list(&free_pages);
>
> For memcg, wonder if we should make it per-memcg-per-zone congested.

Acked-by: Ying Han <yinghan@google.com>

--Ying