Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756246AbZJ0Cnu (ORCPT ); Mon, 26 Oct 2009 22:43:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756152AbZJ0Cns (ORCPT ); Mon, 26 Oct 2009 22:43:48 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:39880 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753557AbZJ0Cm5 (ORCPT ); Mon, 26 Oct 2009 22:42:57 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Mel Gorman Subject: Re: [PATCH 4/5] page allocator: Pre-emptively wake kswapd when high-order watermarks are hit Cc: kosaki.motohiro@jp.fujitsu.com, Frans Pop , Jiri Kosina , Sven Geggus , Karol Lewandowski , Tobias Oetiker , "Rafael J. Wysocki" , David Miller , Reinette Chatre , Kalle Valo , David Rientjes , Mohamed Abbas , Jens Axboe , "John W. Linville" , Pekka Enberg , Bartlomiej Zolnierkiewicz , Greg Kroah-Hartman , Stephan von Krawczynski , Kernel Testers List , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "linux-mm@kvack.org\"" In-Reply-To: <1256221356-26049-5-git-send-email-mel@csn.ul.ie> References: <1256221356-26049-1-git-send-email-mel@csn.ul.ie> <1256221356-26049-5-git-send-email-mel@csn.ul.ie> Message-Id: <20091026235032.2F78.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 27 Oct 2009 11:42:58 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3602 Lines: 102 > When a high-order allocation fails, kswapd is kicked so that it reclaims > at a higher-order to avoid direct reclaimers stall and to help GFP_ATOMIC > allocations. Something has changed in recent kernels that affect the timing > where high-order GFP_ATOMIC allocations are now failing with more frequency, > particularly under pressure. > > This patch pre-emptively checks if watermarks have been hit after a > high-order allocation completes successfully. If the watermarks have been > reached, kswapd is woken in the hope it fixes the watermarks before the > next GFP_ATOMIC allocation fails. > > Warning, this patch is somewhat of a band-aid. If this makes a difference, > it still implies that something has changed that is either causing more > GFP_ATOMIC allocations to occur (such as the case with iwlagn wireless > driver) or make them more likely to fail. hmm, I'm confused. this description addressed generic high order allocation. but, > > Signed-off-by: Mel Gorman > --- > mm/page_alloc.c | 33 ++++++++++++++++++++++----------- > 1 files changed, 22 insertions(+), 11 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7f2aa3e..851df40 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1596,6 +1596,17 @@ try_next_zone: > return page; > } > > +static inline > +void wake_all_kswapd(unsigned int order, struct zonelist *zonelist, > + enum zone_type high_zoneidx) > +{ > + struct zoneref *z; > + struct zone *zone; > + > + for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) > + wakeup_kswapd(zone, order); > +} > + > static inline int > should_alloc_retry(gfp_t gfp_mask, unsigned int order, > unsigned long pages_reclaimed) > @@ -1730,18 +1741,18 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order, __alloc_pages_high_priority() is only called if ALLOC_NO_WATERMARKS. ALLOC_NO_WATERMARKS mean PF_MEMALLOC or TIF_MEMDIE and GFP_ATOMIC don't make nested alloc_pages() (= don't make PF_MEMALLOC case). Then, I haven't understand why this patch improve iwlagn GFP_ATOMIC case. hmm, maybe I missed something. I see the code again tommorow. > congestion_wait(BLK_RW_ASYNC, HZ/50); > } while (!page && (gfp_mask & __GFP_NOFAIL)); > > - return page; > -} > - > -static inline > -void wake_all_kswapd(unsigned int order, struct zonelist *zonelist, > - enum zone_type high_zoneidx) > -{ > - struct zoneref *z; > - struct zone *zone; > + /* > + * If after a high-order allocation we are now below watermarks, > + * pre-emptively kick kswapd rather than having the next allocation > + * fail and have to wake up kswapd, potentially failing GFP_ATOMIC > + * allocations or entering direct reclaim > + */ > + if (unlikely(order) && page && !zone_watermark_ok(preferred_zone, order, > + preferred_zone->watermark[ALLOC_WMARK_LOW], > + zone_idx(preferred_zone), ALLOC_WMARK_LOW)) > + wake_all_kswapd(order, zonelist, high_zoneidx); > > - for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) > - wakeup_kswapd(zone, order); > + return page; > } > > static inline int > -- > 1.6.3.3 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- 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/