Re: [RFC PATCH 1/2] vmscan don't isolate too many pages

[Minchan Kim <minchan.kim@gmail.com>]

On Tue, Jul 7, 2009 at 6:47 PM, KOSAKI
Motohiro<kosaki.motohiro@jp.fujitsu.com> wrote:
> Subject: [PATCH] vmscan don't isolate too many pages
>
> If the system have plenty threads or processes, concurrent reclaim can
> isolate very much pages.
>
> And if other processes isolate _all_ pages on lru, the reclaimer can't find
> any reclaimable page and it makes accidental OOM.
>
> The solusion is, we should restrict maximum number of isolated pages.
> (this patch use inactive_page/2)
>
>
> FAQ
> -------
> Q: Why do you compared zone accumulate pages, not individual zone pages?
> A: If we check individual zone, #-of-reclaimer is restricted by smallest zone.
>   it mean decreasing the performance of the system having small dma zone.
>
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
>  mm/page_alloc.c |   27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> Index: b/mm/page_alloc.c
> ===================================================================
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1721,6 +1721,28 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
>        return alloc_flags;
>  }
>
> +static bool too_many_isolated(struct zonelist *zonelist,
> +                             enum zone_type high_zoneidx, nodemask_t *nodemask)
> +{
> +       unsigned long nr_inactive = 0;
> +       unsigned long nr_isolated = 0;
> +       struct zoneref *z;
> +       struct zone *zone;
> +
> +       for_each_zone_zonelist_nodemask(zone, z, zonelist,
> +                                       high_zoneidx, nodemask) {
> +               if (!populated_zone(zone))
> +                       continue;
> +
> +               nr_inactive += zone_page_state(zone, NR_INACTIVE_ANON);
> +               nr_inactive += zone_page_state(zone, NR_INACTIVE_FILE);
> +               nr_isolated += zone_page_state(zone, NR_ISOLATED_ANON);
> +               nr_isolated += zone_page_state(zone, NR_ISOLATED_FILE);
> +       }
> +
> +       return nr_isolated > nr_inactive;
> +}
> +
>  static inline struct page *
>  __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>        struct zonelist *zonelist, enum zone_type high_zoneidx,
> @@ -1789,6 +1811,11 @@ rebalance:
>        if (p->flags & PF_MEMALLOC)
>                goto nopage;
>
> +       if (too_many_isolated(gfp_mask, zonelist, high_zoneidx, nodemask)) {

too_many_isolated(zonelist, high_zoneidx, nodemask)

-- 
Kind regards,
Minchan Kim

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