From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id A988A6B005C for ; Tue, 21 Apr 2009 20:25:50 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n3M0QDLk003793 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 22 Apr 2009 09:26:13 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 8C4B645DE6B for ; Wed, 22 Apr 2009 09:26:12 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 4666945DE61 for ; Wed, 22 Apr 2009 09:26:12 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 0C1DDE38012 for ; Wed, 22 Apr 2009 09:26:12 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 0538BE38004 for ; Wed, 22 Apr 2009 09:26:11 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 21/25] Use allocation flags as an index to the zone watermark In-Reply-To: <1240266011-11140-22-git-send-email-mel@csn.ul.ie> References: <1240266011-11140-1-git-send-email-mel@csn.ul.ie> <1240266011-11140-22-git-send-email-mel@csn.ul.ie> Message-Id: <20090422092429.6271.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 22 Apr 2009 09:26:10 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Linux Memory Management List , Christoph Lameter , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra , Pekka Enberg , Andrew Morton List-ID: > ALLOC_WMARK_MIN, ALLOC_WMARK_LOW and ALLOC_WMARK_HIGH determin whether > pages_min, pages_low or pages_high is used as the zone watermark when > allocating the pages. Two branches in the allocator hotpath determine which > watermark to use. This patch uses the flags as an array index and places > the three watermarks in a union with an array so it can be offset. This > means the flags can be used as an array index and reduces the branches > taken. > > Signed-off-by: Mel Gorman > Reviewed-by: Christoph Lameter > --- > include/linux/mmzone.h | 8 +++++++- > mm/page_alloc.c | 18 ++++++++---------- > 2 files changed, 15 insertions(+), 11 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index f82bdba..c1fa208 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -275,7 +275,13 @@ struct zone_reclaim_stat { > > struct zone { > /* Fields commonly accessed by the page allocator */ > - unsigned long pages_min, pages_low, pages_high; > + union { > + struct { > + unsigned long pages_min, pages_low, pages_high; > + }; > + unsigned long pages_mark[3]; > + }; > + hmmm... I don't like union hack. Why can't we change all caller to use page_mark? > /* > * We don't know if the memory that we're going to allocate will be freeable > * or/and it will be released eventually, so to avoid totally wasting several > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 376d848..e61867e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1157,10 +1157,13 @@ failed: > return NULL; > } > > -#define ALLOC_NO_WATERMARKS 0x01 /* don't check watermarks at all */ > -#define ALLOC_WMARK_MIN 0x02 /* use pages_min watermark */ > -#define ALLOC_WMARK_LOW 0x04 /* use pages_low watermark */ > -#define ALLOC_WMARK_HIGH 0x08 /* use pages_high watermark */ > +/* The WMARK bits are used as an index zone->pages_mark */ > +#define ALLOC_WMARK_MIN 0x00 /* use pages_min watermark */ > +#define ALLOC_WMARK_LOW 0x01 /* use pages_low watermark */ > +#define ALLOC_WMARK_HIGH 0x02 /* use pages_high watermark */ > +#define ALLOC_NO_WATERMARKS 0x08 /* don't check watermarks at all */ > +#define ALLOC_WMARK_MASK 0x07 /* Mask to get the watermark bits */ the mask only use two bit. but mask definition is three bit (0x07), why? > + > #define ALLOC_HARDER 0x10 /* try to alloc harder */ > #define ALLOC_HIGH 0x20 /* __GFP_HIGH set */ > #ifdef CONFIG_CPUSETS > @@ -1463,12 +1466,7 @@ zonelist_scan: > > if (!(alloc_flags & ALLOC_NO_WATERMARKS)) { > unsigned long mark; > - if (alloc_flags & ALLOC_WMARK_MIN) > - mark = zone->pages_min; > - else if (alloc_flags & ALLOC_WMARK_LOW) > - mark = zone->pages_low; > - else > - mark = zone->pages_high; > + mark = zone->pages_mark[alloc_flags & ALLOC_WMARK_MASK]; > if (!zone_watermark_ok(zone, order, mark, > classzone_idx, alloc_flags)) { > if (!zone_reclaim_mode || > -- > 1.5.6.5 > -- 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