Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755484AbaFWNc2 (ORCPT ); Mon, 23 Jun 2014 09:32:28 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47949 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754410AbaFWNc0 (ORCPT ); Mon, 23 Jun 2014 09:32:26 -0400 Date: Mon, 23 Jun 2014 14:32:21 +0100 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , Rik van Riel , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 3/4] mm: vmscan: remove all_unreclaimable() Message-ID: <20140623133221.GN10819@suse.de> References: <1403282030-29915-1-git-send-email-hannes@cmpxchg.org> <1403282030-29915-3-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1403282030-29915-3-git-send-email-hannes@cmpxchg.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 20, 2014 at 12:33:49PM -0400, Johannes Weiner wrote: > Direct reclaim currently calls shrink_zones() to reclaim all members > of a zonelist, and if that wasn't successful it does another pass > through the same zonelist to check overall reclaimability. > > Just check reclaimability in shrink_zones() directly and propagate the > result through the return value. Then remove all_unreclaimable(). > > Signed-off-by: Johannes Weiner > --- > mm/vmscan.c | 48 +++++++++++++++++++++++------------------------- > 1 file changed, 23 insertions(+), 25 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ed1efb84c542..d0bc1a209746 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2244,9 +2244,10 @@ static inline bool should_continue_reclaim(struct zone *zone, > } > } > > -static void shrink_zone(struct zone *zone, struct scan_control *sc) > +static unsigned long shrink_zone(struct zone *zone, struct scan_control *sc) > { > unsigned long nr_reclaimed, nr_scanned; > + unsigned long zone_reclaimed = 0; > > do { > struct mem_cgroup *root = sc->target_mem_cgroup; > @@ -2290,8 +2291,12 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc) > sc->nr_scanned - nr_scanned, > sc->nr_reclaimed - nr_reclaimed); > > + zone_reclaimed += sc->nr_reclaimed - nr_reclaimed; > + > } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed, > sc->nr_scanned - nr_scanned, sc)); > + > + return zone_reclaimed; > } You do not actually need a counter here because all that matters is that a page got reclaimed. It could just as easily have been bool zone_reclaimable = false; ... if (sc->nr_reclaimed - nr_reclaimed) zone_reclaimable = true; ... return zone_reclaimable so that zone[s]_reclaimable is always a boolean and not sometimes a boolean and sometimes a counter. > > /* Returns true if compaction should go ahead for a high-order request */ > @@ -2340,8 +2345,10 @@ static inline bool compaction_ready(struct zone *zone, int order) > * > * If a zone is deemed to be full of pinned pages then just give it a light > * scan then give up on it. > + * > + * Returns whether the zones overall are reclaimable or not. > */ Returns true if a zone was reclaimable > -static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > +static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > { > struct zoneref *z; > struct zone *zone; > @@ -2354,6 +2361,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > .gfp_mask = sc->gfp_mask, > }; > enum zone_type requested_highidx = gfp_zone(sc->gfp_mask); > + bool all_unreclaimable = true; > > /* > * If the number of buffer_heads in the machine exceeds the maximum > @@ -2368,6 +2376,8 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > > for_each_zone_zonelist_nodemask(zone, z, zonelist, > gfp_zone(sc->gfp_mask), sc->nodemask) { > + unsigned long zone_reclaimed = 0; > + > if (!populated_zone(zone)) > continue; > /* > @@ -2414,10 +2424,15 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > &nr_soft_scanned); > sc->nr_reclaimed += nr_soft_reclaimed; > sc->nr_scanned += nr_soft_scanned; > + zone_reclaimed += nr_soft_reclaimed; > /* need some check for avoid more shrink_zone() */ > } > > - shrink_zone(zone, sc); > + zone_reclaimed += shrink_zone(zone, sc); > + > + if (zone_reclaimed || > + (global_reclaim(sc) && zone_reclaimable(zone))) > + all_unreclaimable = false; > } > This is where you don't need the counter as such. It could just as easily have been bool reclaimable = false; .... if (shrink_zone(zone, sc)) reclaimable = true; if (!reclaimable && global_reclaim(sc) && zone_reclaimable(zone)) reclaimable = true; return reclaimable; It doesn't matter as such, it's just zone_reclaimed is implemented as a counter but not used as one. > /* > @@ -2439,26 +2454,8 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) > * promoted it to __GFP_HIGHMEM. > */ > sc->gfp_mask = orig_mask; > -} > > -/* All zones in zonelist are unreclaimable? */ > -static bool all_unreclaimable(struct zonelist *zonelist, > - struct scan_control *sc) > -{ > - struct zoneref *z; > - struct zone *zone; > - > - 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)) > - return false; > - } > - > - return true; > + return !all_unreclaimable; > } > > /* > @@ -2482,6 +2479,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, > { > unsigned long total_scanned = 0; > unsigned long writeback_threshold; > + bool zones_reclaimable; > > delayacct_freepages_start(); > > @@ -2492,7 +2490,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, > vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, > sc->priority); > sc->nr_scanned = 0; > - shrink_zones(zonelist, sc); > + zones_reclaimable = shrink_zones(zonelist, sc); > > total_scanned += sc->nr_scanned; > if (sc->nr_reclaimed >= sc->nr_to_reclaim) > @@ -2533,8 +2531,8 @@ out: > if (sc->compaction_ready) > return 1; > > - /* top priority shrink_zones still had more to do? don't OOM, then */ > - if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) > + /* Any of the zones still reclaimable? Don't OOM. */ > + if (zones_reclaimable) > return 1; > > return 0; > -- > 2.0.0 > -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/