From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751921AbaJ0Gpj (ORCPT ); Mon, 27 Oct 2014 02:45:39 -0400 Received: from lgeamrelo02.lge.com ([156.147.1.126]:33523 "EHLO lgeamrelo02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965AbaJ0Gpi (ORCPT ); Mon, 27 Oct 2014 02:45:38 -0400 X-Original-SENDERIP: 10.177.222.213 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Mon, 27 Oct 2014 15:46:51 +0900 From: Joonsoo Kim To: Vlastimil Babka Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , Mel Gorman , Michal Nazarewicz , Naoya Horiguchi , Christoph Lameter , Rik van Riel , David Rientjes Subject: Re: [PATCH 1/5] mm, compaction: pass classzone_idx and alloc_flags to watermark checking Message-ID: <20141027064651.GA23379@js1304-P5Q-DELUXE> References: <1412696019-21761-1-git-send-email-vbabka@suse.cz> <1412696019-21761-2-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412696019-21761-2-git-send-email-vbabka@suse.cz> 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 Tue, Oct 07, 2014 at 05:33:35PM +0200, Vlastimil Babka wrote: > Compaction relies on zone watermark checks for decisions such as if it's worth > to start compacting in compaction_suitable() or whether compaction should stop > in compact_finished(). The watermark checks take classzone_idx and alloc_flags > parameters, which are related to the memory allocation request. But from the > context of compaction they are currently passed as 0, including the direct > compaction which is invoked to satisfy the allocation request, and could > therefore know the proper values. > > The lack of proper values can lead to mismatch between decisions taken during > compaction and decisions related to the allocation request. Lack of proper > classzone_idx value means that lowmem_reserve is not taken into account. > This has manifested (during recent changes to deferred compaction) when DMA > zone was used as fallback for preferred Normal zone. compaction_suitable() > without proper classzone_idx would think that the watermarks are already > satisfied, but watermark check in get_page_from_freelist() would fail. Because > of this problem, deferring compaction has extra complexity that can be removed > in the following patch. > > The issue (not confirmed in practice) with missing alloc_flags is opposite in > nature. For allocations that include ALLOC_HIGH, ALLOC_HIGHER or ALLOC_CMA in > alloc_flags (the last includes all MOVABLE allocations on CMA-enabled systems) > the watermark checking in compaction with 0 passed will be stricter than in > get_page_from_freelist(). In these cases compaction might be running for a > longer time than is really needed. > > This patch fixes these problems by adding alloc_flags and classzone_idx to > struct compact_control and related functions involved in direct compaction and > watermark checking. Where possible, all other callers of compaction_suitable() > pass proper values where those are known. This is currently limited to > classzone_idx, which is sometimes known in kswapd context. However, the direct > reclaim callers should_continue_reclaim() and compaction_ready() do not > currently know the proper values, so the coordination between reclaim and > compaction may still not be as accurate as it could. This can be fixed later, > if it's shown to be an issue. > > The effect of this patch should be slightly better high-order allocation > success rates and/or less compaction overhead, depending on the type of > allocations and presence of CMA. It allows simplifying deferred compaction > code in a followup patch. > > When testing with stress-highalloc, there was some slight improvement (which > might be just due to variance) in success rates of non-THP-like allocations. > > Signed-off-by: Vlastimil Babka > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Joonsoo Kim > Cc: Michal Nazarewicz > Cc: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > Cc: David Rientjes > --- > include/linux/compaction.h | 8 ++++++-- > mm/compaction.c | 29 +++++++++++++++-------------- > mm/internal.h | 2 ++ > mm/page_alloc.c | 1 + > mm/vmscan.c | 12 ++++++------ > 5 files changed, 30 insertions(+), 22 deletions(-) > > diff --git a/include/linux/compaction.h b/include/linux/compaction.h > index 60bdf8d..d896765 100644 > --- a/include/linux/compaction.h > +++ b/include/linux/compaction.h > @@ -33,10 +33,12 @@ extern int fragmentation_index(struct zone *zone, unsigned int order); > extern unsigned long try_to_compact_pages(struct zonelist *zonelist, > int order, gfp_t gfp_mask, nodemask_t *mask, > enum migrate_mode mode, int *contended, > + int alloc_flags, int classzone_idx, > struct zone **candidate_zone); > extern void compact_pgdat(pg_data_t *pgdat, int order); > extern void reset_isolation_suitable(pg_data_t *pgdat); > -extern unsigned long compaction_suitable(struct zone *zone, int order); > +extern unsigned long compaction_suitable(struct zone *zone, int order, > + int alloc_flags, int classzone_idx); > > /* Do not skip compaction more than 64 times */ > #define COMPACT_MAX_DEFER_SHIFT 6 > @@ -103,6 +105,7 @@ static inline bool compaction_restarting(struct zone *zone, int order) > static inline unsigned long try_to_compact_pages(struct zonelist *zonelist, > int order, gfp_t gfp_mask, nodemask_t *nodemask, > enum migrate_mode mode, int *contended, > + int alloc_flags, int classzone_idx, > struct zone **candidate_zone) > { > return COMPACT_CONTINUE; > @@ -116,7 +119,8 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat) > { > } > > -static inline unsigned long compaction_suitable(struct zone *zone, int order) > +static inline unsigned long compaction_suitable(struct zone *zone, int order, > + int alloc_flags, int classzone_idx) > { > return COMPACT_SKIPPED; > } > diff --git a/mm/compaction.c b/mm/compaction.c > index edba18a..dba8891 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1069,9 +1069,9 @@ static int compact_finished(struct zone *zone, struct compact_control *cc, > > /* Compaction run is not finished if the watermark is not met */ > watermark = low_wmark_pages(zone); > - watermark += (1 << cc->order); > > - if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) > + if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, > + cc->alloc_flags)) > return COMPACT_CONTINUE; > > /* Direct compactor: Is a suitable page free? */ > @@ -1097,7 +1097,8 @@ static int compact_finished(struct zone *zone, struct compact_control *cc, > * COMPACT_PARTIAL - If the allocation would succeed without compaction > * COMPACT_CONTINUE - If compaction should run now > */ > -unsigned long compaction_suitable(struct zone *zone, int order) > +unsigned long compaction_suitable(struct zone *zone, int order, > + int alloc_flags, int classzone_idx) > { > int fragindex; > unsigned long watermark; > @@ -1134,7 +1135,7 @@ unsigned long compaction_suitable(struct zone *zone, int order) > return COMPACT_SKIPPED; > > if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark, > - 0, 0)) > + classzone_idx, alloc_flags)) > return COMPACT_PARTIAL; Hello, compaction_suitable() has one more zone_watermark_ok(). Why is it unchanged? Thanks.