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

Wu Fengguang
2009-07-07T13:24:17Z

On Tue, Jul 07, 2009 at 05:47:13PM +0800, KOSAKI Motohiro 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)

Now I think this is a better solution than per-cpu throttling :)
Will test it tomorrow.

Acked-by: Wu Fengguang <fengguang.wu@intel.com>

>
> 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)) {
> + schedule_timeout_uninterruptible(HZ/10);
> + goto restart;
> + }
> +
> /* Try direct reclaim and then allocating */
> page = __alloc_pages_direct_reclaim(gfp_mask, order,
> zonelist, high_zoneidx,
>