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Date: Sun, 12 Sep 2010 19:42:53 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Minchan Kim <minchan.kim@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"linux-mm" <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>,
Rik van Riel <riel@...hat.com>,
"M. Vefa Bicakci" <bicave@...eronline.com>, stable@...nel.org
Subject: Re: [PATCH v2] vmscan: check all_unreclaimable in direct reclaim path
On Sunday, September 12, 2010, Minchan Kim wrote:
> Adnrew, Please drop my old version and merge this verstion.
> (old : vmscan-check-all_unreclaimable-in-direct-reclaim-path.patch)
>
> * Changelog from v2
> * remove inline - suggested by Andrew
> * add function desription - suggeseted by Adnrew
>
> == CUT HERE ==
For the record, this commit:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6715045ddc7472a22be5e49d4047d2d89b391f45
is reported to fix the problem without the $subject patch (see
http://lkml.org/lkml/2010/9/11/129). So, I'm not sure if it's still necessary
to special case this particular situation?
Thanks,
Rafael
> Subject: [PATCH v2] vmscan: check all_unreclaimable in direct reclaim path
>
> M. Vefa Bicakci reported 2.6.35 kernel hang up when hibernation on his
> 32bit 3GB mem machine. (https://bugzilla.kernel.org/show_bug.cgi?id=16771)
> Also he was bisected first bad commit is below
>
> commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
> Author: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Date: Fri Jun 4 14:15:05 2010 -0700
>
> vmscan: fix do_try_to_free_pages() return value when priority==0 reclaim failure
>
> At first impression, this seemed very strange because the above commit only
> chenged function return value and hibernate_preallocate_memory() ignore
> return value of shrink_all_memory(). But it's related.
>
> Now, page allocation from hibernation code may enter infinite loop if
> the system has highmem. The reasons are that vmscan don't care enough
> OOM case when oom_killer_disabled.
>
> The problem sequence is following as.
>
> 1. hibernation
> 2. oom_disable
> 3. alloc_pages
> 4. do_try_to_free_pages
> if (scanning_global_lru(sc) && !all_unreclaimable)
> return 1;
>
> If kswapd is not freezed, it would set zone->all_unreclaimable to 1 and then
> shrink_zones maybe return true(ie, all_unreclaimable is true).
> so at last, alloc_pages could go to _nopage_. If it is, it should have no problem.
>
> This patch adds all_unreclaimable check to protect in direct reclaim path, too.
> It can care of hibernation OOM case and help bailout all_unreclaimable case slightly.
>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: M. Vefa Bicakci <bicave@...eronline.com>
> Cc: stable@...nel.org
> Acked-by: Rafael J. Wysocki <rjw@...k.pl>
> Reviewed-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> ---
> mm/vmscan.c | 46 ++++++++++++++++++++++++++++++++++++++--------
> 1 files changed, 38 insertions(+), 8 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7870893..ecae0ef 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1877,12 +1877,11 @@ static void shrink_zone(int priority, struct zone *zone,
> * If a zone is deemed to be full of pinned pages then just give it a light
> * scan then give up on it.
> */
> -static bool shrink_zones(int priority, struct zonelist *zonelist,
> +static void shrink_zones(int priority, struct zonelist *zonelist,
> struct scan_control *sc)
> {
> struct zoneref *z;
> struct zone *zone;
> - bool all_unreclaimable = true;
>
> for_each_zone_zonelist_nodemask(zone, z, zonelist,
> gfp_zone(sc->gfp_mask), sc->nodemask) {
> @@ -1900,8 +1899,41 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
> }
>
> shrink_zone(priority, zone, sc);
> - all_unreclaimable = false;
> }
> +}
> +
> +static bool zone_reclaimable(struct zone *zone)
> +{
> + return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
> +}
> +
> +/*
> + * As hibernation is going on, kswapd is freezed so that it can't mark
> + * the zone into all_unreclaimable. It can't handle OOM during hibernation.
> + * So let's check zone's unreclaimable in direct reclaim as well as kswapd.
> + */
> +static bool all_unreclaimable(struct zonelist *zonelist,
> + struct scan_control *sc)
> +{
> + struct zoneref *z;
> + struct zone *zone;
> + bool all_unreclaimable = true;
> +
> + if (!scanning_global_lru(sc))
> + return false;
> +
> + for_each_zone_zonelist_nodemask(zone, z, zonelist,
> + gfp_zone(sc->gfp_mask), sc->nodemask) {
> + if (!populated_zone(zone))
> + continue;
> + if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> + continue;
> + if (zone_reclaimable(zone)) {
> + all_unreclaimable = false;
> + break;
> + }
> + }
> +
> return all_unreclaimable;
> }
>
> @@ -1925,7 +1957,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> struct scan_control *sc)
> {
> int priority;
> - bool all_unreclaimable;
> unsigned long total_scanned = 0;
> struct reclaim_state *reclaim_state = current->reclaim_state;
> struct zoneref *z;
> @@ -1942,7 +1973,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
> sc->nr_scanned = 0;
> if (!priority)
> disable_swap_token();
> - all_unreclaimable = shrink_zones(priority, zonelist, sc);
> + shrink_zones(priority, zonelist, sc);
> /*
> * Don't shrink slabs when reclaiming memory from
> * over limit cgroups
> @@ -2004,7 +2035,7 @@ out:
> return sc->nr_reclaimed;
>
> /* top priority shrink_zones still had more to do? don't OOM, then */
> - if (scanning_global_lru(sc) && !all_unreclaimable)
> + if (!all_unreclaimable(zonelist, sc))
> return 1;
>
> return 0;
> @@ -2270,8 +2301,7 @@ loop_again:
> total_scanned += sc.nr_scanned;
> if (zone->all_unreclaimable)
> continue;
> - if (nr_slab == 0 &&
> - zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
> + if (nr_slab == 0 && !zone_reclaimable(zone))
> zone->all_unreclaimable = 1;
> /*
> * If we've done a decent amount of scanning and
>
--
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