On Tue, Aug 06, 2013 at 06:42:06PM -0700, Lisa Du wrote: > Hi, Michal and all > I'm so sorry, now I updated the review list. > Thank you all for the review and comments! > > In this version: > Remove change ID according to Minchan's comment; > Reorder the check in shrink_zones according Johannes's comment. > Also cc to more people. > > >From ff345123117394c6b9b838bf54eb935bfa879f32 Mon Sep 17 00:00:00 2001 > From: Lisa Du <cldu@xxxxxxxxxxx> > Date: Mon, 5 Aug 2013 09:26:57 +0800 > Subject: [PATCH] mm: vmscan: fix do_try_to_free_pages() livelock > > This patch is based on KOSAKI's work and I add a little more > description, please refer https://lkml.org/lkml/2012/6/14/74. > > Currently, I found system can enter a state that there are lots > of free pages in a zone but only order-0 and order-1 pages which > means the zone is heavily fragmented, then high order allocation > could make direct reclaim path's long stall(ex, 60 seconds) > especially in no swap and no compaciton enviroment. This problem > happened on v3.4, but it seems issue still lives in current tree, > the reason is do_try_to_free_pages enter live lock: > > kswapd will go to sleep if the zones have been fully scanned > and are still not balanced. As kswapd thinks there's little point > trying all over again to avoid infinite loop. Instead it changes > order from high-order to 0-order because kswapd think order-0 is the > most important. Look at 73ce02e9 in detail. If watermarks are ok, > kswapd will go back to sleep and may leave zone->all_unreclaimable = 0. > It assume high-order users can still perform direct reclaim if they wish. > > Direct reclaim continue to reclaim for a high order which is not a > COSTLY_ORDER without oom-killer until kswapd turn on zone->all_unreclaimble. > This is because to avoid too early oom-kill. So it means direct_reclaim > depends on kswapd to break this loop. > > In worst case, direct-reclaim may continue to page reclaim forever > when kswapd sleeps forever until someone like watchdog detect and finally > kill the process. As described in: > http://thread.gmane.org/gmane.linux.kernel.mm/103737 > > We can't turn on zone->all_unreclaimable from direct reclaim path > because direct reclaim path don't take any lock and this way is racy. > Thus this patch removes zone->all_unreclaimable field completely and > recalculates zone reclaimable state every time. > > Note: we can't take the idea that direct-reclaim see zone->pages_scanned > directly and kswapd continue to use zone->all_unreclaimable. Because, it > is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use > zone->all_unreclaimable as a name) describes the detail. > > Cc: Aaditya Kumar <aaditya.kumar.30@xxxxxxxxx> > Cc: Ying Han <yinghan@xxxxxxxxxx> > Cc: Nick Piggin <npiggin@xxxxxxxxx> > Acked-by: Rik van Riel <riel@xxxxxxxxxx> > Cc: Mel Gorman <mel@xxxxxxxxx> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Cc: Christoph Lameter <cl@xxxxxxxxx> > Cc: Bob Liu <lliubbo@xxxxxxxxx> > Cc: Neil Zhang <zhangwm@xxxxxxxxxxx> > Cc: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> > Acked-by: Minchan Kim <minchan@xxxxxxxxxx> > Reviewed-by: Michal Hocko <mhocko@xxxxxxx> > Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx> I sent an Acked-by, please keep these tags verbatim. > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Signed-off-by: Lisa Du <cldu@xxxxxxxxxxx> > @@ -2244,8 +2244,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > if (global_reclaim(sc)) { > if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) > continue; > - if (zone->all_unreclaimable && > - sc->priority != DEF_PRIORITY) > + if (sc->priority != DEF_PRIORITY && > + !zone_reclaimable(zone)) > continue; /* Let kswapd poll it */ > if (IS_ENABLED(CONFIG_COMPACTION)) { > /* Yes, this is better, thanks. > @@ -2901,7 +2892,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > if (!populated_zone(zone)) > continue; > > - if (zone->all_unreclaimable && > + if (!zone_reclaimable(zone) && > sc.priority != DEF_PRIORITY) > continue; > > @@ -2980,7 +2971,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > if (!populated_zone(zone)) > continue; > > - if (zone->all_unreclaimable && > + if (!zone_reclaimable(zone) && > sc.priority != DEF_PRIORITY) > continue; > What about those? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>