Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964778AbWAZP4j (ORCPT ); Thu, 26 Jan 2006 10:56:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932371AbWAZP4j (ORCPT ); Thu, 26 Jan 2006 10:56:39 -0500 Received: from holly.csn.ul.ie ([136.201.105.4]:53139 "EHLO holly.csn.ul.ie") by vger.kernel.org with ESMTP id S932370AbWAZP4i (ORCPT ); Thu, 26 Jan 2006 10:56:38 -0500 Date: Thu, 26 Jan 2006 15:55:13 +0000 (GMT) From: Mel Gorman X-X-Sender: mel@skynet To: Marcelo Tosatti Cc: linux-mm@kvack.org, jschopp@austin.ibm.com, linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, lhms-devel@lists.sourceforge.net Subject: Re: [PATCH 2/4] Split the free lists into kernel and user parts In-Reply-To: <20060123191341.GA4892@dmt.cnet> Message-ID: References: <20060120115415.16475.8529.sendpatchset@skynet.csn.ul.ie> <20060120115455.16475.93688.sendpatchset@skynet.csn.ul.ie> <20060122133147.GA4186@dmt.cnet> <20060123191341.GA4892@dmt.cnet> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4560 Lines: 98 On Mon, 23 Jan 2006, Marcelo Tosatti wrote: > On Mon, Jan 23, 2006 at 09:39:16AM +0000, Mel Gorman wrote: > > On Sun, 22 Jan 2006, Marcelo Tosatti wrote: > > > > > Hi Mel, > > > > > > On Fri, Jan 20, 2006 at 11:54:55AM +0000, Mel Gorman wrote: > > > > > > > > This patch adds the core of the anti-fragmentation strategy. It works by > > > > grouping related allocation types together. The idea is that large groups of > > > > pages that may be reclaimed are placed near each other. The zone->free_area > > > > list is broken into RCLM_TYPES number of lists. > > > > > > > > Signed-off-by: Mel Gorman > > > > Signed-off-by: Joel Schopp > > > > diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.16-rc1-mm1-001_antifrag_flags/include/linux/mmzone.h linux-2.6.16-rc1-mm1-002_fragcore/include/linux/mmzone.h > > > > --- linux-2.6.16-rc1-mm1-001_antifrag_flags/include/linux/mmzone.h 2006-01-19 11:21:59.000000000 +0000 > > > > +++ linux-2.6.16-rc1-mm1-002_fragcore/include/linux/mmzone.h 2006-01-19 21:51:05.000000000 +0000 > > > > @@ -22,8 +22,16 @@ > > > > #define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER > > > > #endif > > > > > > > > +#define RCLM_NORCLM 0 > > > > +#define RCLM_EASY 1 > > > > +#define RCLM_TYPES 2 > > > > + > > > > +#define for_each_rclmtype_order(type, order) \ > > > > + for (order = 0; order < MAX_ORDER; order++) \ > > > > + for (type = 0; type < RCLM_TYPES; type++) > > > > + > > > > struct free_area { > > > > - struct list_head free_list; > > > > + struct list_head free_list[RCLM_TYPES]; > > > > unsigned long nr_free; > > > > }; > > > > > > > > diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.16-rc1-mm1-001_antifrag_flags/include/linux/page-flags.h linux-2.6.16-rc1-mm1-002_fragcore/include/linux/page-flags.h > > > > --- linux-2.6.16-rc1-mm1-001_antifrag_flags/include/linux/page-flags.h 2006-01-19 11:21:59.000000000 +0000 > > > > +++ linux-2.6.16-rc1-mm1-002_fragcore/include/linux/page-flags.h 2006-01-19 21:51:05.000000000 +0000 > > > > @@ -76,6 +76,7 @@ > > > > #define PG_reclaim 17 /* To be reclaimed asap */ > > > > #define PG_nosave_free 18 /* Free, should not be written */ > > > > #define PG_uncached 19 /* Page has been mapped as uncached */ > > > > +#define PG_easyrclm 20 /* Page is in an easy reclaim block */ > > > > > > > > /* > > > > * Global page accounting. One instance per CPU. Only unsigned longs are > > > > @@ -345,6 +346,12 @@ extern void __mod_page_state_offset(unsi > > > > #define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags) > > > > #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags) > > > > > > > > +#define PageEasyRclm(page) test_bit(PG_easyrclm, &(page)->flags) > > > > +#define SetPageEasyRclm(page) set_bit(PG_easyrclm, &(page)->flags) > > > > +#define ClearPageEasyRclm(page) clear_bit(PG_easyrclm, &(page)->flags) > > > > +#define __SetPageEasyRclm(page) __set_bit(PG_easyrclm, &(page)->flags) > > > > +#define __ClearPageEasyRclm(page) __clear_bit(PG_easyrclm, &(page)->flags) > > > > + > > > > > > You can't read/write to page->flags non-atomically, except when you > > > guarantee that the page is not visible to other CPU's (eg at the very > > > end of the page freeing code). > > > > > > > The helper PageEasyRclm is only used when either the spinlock is held or a > > per-cpu page is being released so it should be safe. The Set and Clear > > helpers are only used with a spinlock held. > > Mel, > > Other codepaths which touch page->flags do not hold any lock, so you > really must use atomic operations, except when you've guarantee that the > page is being freed and won't be reused. > Understood, so I took another look to be sure; PageEasyRclm() is used on pages that are about to be freed to the main or per-cpu allocator so it should be safe. __SetPageEasyRclm is called when the page is about to be freed. It should be safe from concurrent access. __ClearPageEasyRclm is called when the page is about to be allocated. It should be safe. I think it is guaranteed that there are on concurrent accessing of the page flags. Is there something I have missed? -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - 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/