linux-kernel - Re: [PATCH RFC] mm: reset pages_scanned only when free pages are above high watermark

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Date:	Wed, 18 Mar 2015 14:48:32 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	linux-mm@...ck.org
CC:	Roman Gushchin <klamm@...dex-team.ru>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH RFC] mm: reset pages_scanned only when free pages are
 above high watermark

On 03/11/2015 07:30 PM, Konstantin Khlebnikov wrote:
> Technically, this counter works as OOM-countdown. Let's reset it only
> when zone is completely recovered and ready to handle any allocations.
> Otherwise system could never recover and stuck in livelock.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

Hmm, could this help in cases like this one?
https://lkml.org/lkml/2015/1/23/688

> ---
>   mm/page_alloc.c |    6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ffd5ad2a6e10..ef7795c8c121 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -701,7 +701,8 @@ static void free_pcppages_bulk(struct zone *zone, int count,
>
>   	spin_lock(&zone->lock);
>   	nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
> -	if (nr_scanned)
> +	if (nr_scanned &&
> +	    zone_page_state(zone, NR_FREE_PAGES) > high_wmark_pages(zone))
>   		__mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
>
>   	while (to_free) {
> @@ -752,7 +753,8 @@ static void free_one_page(struct zone *zone,
>   	unsigned long nr_scanned;
>   	spin_lock(&zone->lock);
>   	nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
> -	if (nr_scanned)
> +	if (nr_scanned &&
> +	    zone_page_state(zone, NR_FREE_PAGES) > high_wmark_pages(zone))
>   		__mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
>
>   	if (unlikely(has_isolate_pageblock(zone) ||
>
> --
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