From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx103.postini.com [74.125.245.103]) by kanga.kvack.org (Postfix) with SMTP id 1E1B86B002B for ; Mon, 24 Sep 2012 05:31:52 -0400 (EDT) Received: from epcpsbgm1.samsung.com (epcpsbgm1 [203.254.230.26]) by mailout1.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MAU00K9JL4FVD10@mailout1.samsung.com> for linux-mm@kvack.org; Mon, 24 Sep 2012 18:31:49 +0900 (KST) Received: from amdc1032.localnet ([106.116.147.136]) by mmp2.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTPA id <0MAU003APL4ZUU30@mmp2.samsung.com> for linux-mm@kvack.org; Mon, 24 Sep 2012 18:31:49 +0900 (KST) From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH v4 4/4] cma: fix watermark checking Date: Mon, 24 Sep 2012 11:30:43 +0200 References: <1347632974-20465-1-git-send-email-b.zolnierkie@samsung.com> <1347632974-20465-5-git-send-email-b.zolnierkie@samsung.com> <20120919125102.4a45e27c.akpm@linux-foundation.org> In-reply-to: <20120919125102.4a45e27c.akpm@linux-foundation.org> MIME-version: 1.0 Message-id: <201209241130.43480.b.zolnierkie@samsung.com> Content-type: Text/Plain; charset=us-ascii Content-transfer-encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, m.szyprowski@samsung.com, mina86@mina86.com, minchan@kernel.org, mgorman@suse.de, hughd@google.com, kyungmin.park@samsung.com On Wednesday 19 September 2012 21:51:02 Andrew Morton wrote: > On Fri, 14 Sep 2012 16:29:34 +0200 > Bartlomiej Zolnierkiewicz wrote: > > > * Add ALLOC_CMA alloc flag and pass it to [__]zone_watermark_ok() > > (from Minchan Kim). > > What is its meaning and why was it added. ALLOC_CMA flag means that allocation can use CMA areas to get free pages from. Free CMA pages are accounted by system as normal free pages (NR_FREE_PAGES) but they can be used only by movable type allocations (otherwise they cannot be migrated once we want to do CMA allocation) so we have to fix free_pages in __zone_watermark_ok() or the watermark check will be too optimistic for unmovable allocations. > > * During watermark check decrease available free pages number by > > free CMA pages number if necessary (unmovable allocations cannot > > use pages from CMA areas). > > > > ... > > > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -231,6 +231,21 @@ enum zone_watermarks { > > #define low_wmark_pages(z) (z->watermark[WMARK_LOW]) > > #define high_wmark_pages(z) (z->watermark[WMARK_HIGH]) > > > > +/* The ALLOC_WMARK bits are used as an index to zone->watermark */ > > +#define ALLOC_WMARK_MIN WMARK_MIN > > +#define ALLOC_WMARK_LOW WMARK_LOW > > +#define ALLOC_WMARK_HIGH WMARK_HIGH > > +#define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */ > > + > > +/* Mask to get the watermark bits */ > > +#define ALLOC_WMARK_MASK (ALLOC_NO_WATERMARKS-1) > > + > > +#define ALLOC_HARDER 0x10 /* try to alloc harder */ > > +#define ALLOC_HIGH 0x20 /* __GFP_HIGH set */ > > +#define ALLOC_CPUSET 0x40 /* check for correct cpuset */ > > + > > Unneeded newline. > > > +#define ALLOC_CMA 0x80 > > All the other enumerations were documented. ALLOC_CMA was left > undocumented, despite sorely needing documentation. > > > struct per_cpu_pages { > > int count; /* number of pages in the list */ > > int high; /* high watermark, emptying needed */ > > diff --git a/mm/compaction.c b/mm/compaction.c > > index 4b902aa..36d79ea 100644 > > --- a/mm/compaction.c > > +++ b/mm/compaction.c > > @@ -868,6 +868,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist, > > struct zoneref *z; > > struct zone *zone; > > int rc = COMPACT_SKIPPED; > > + int alloc_flags = 0; > > > > /* > > * Check whether it is worth even starting compaction. The order check is > > @@ -879,6 +880,10 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist, > > > > count_vm_event(COMPACTSTALL); > > > > +#ifdef CONFIG_CMA > > + if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE) > > + alloc_flags |= ALLOC_CMA; > > I find this rather obscure. What is the significance of > MIGRATE_MOVABLE here? If it had been > > : if (allocflags_to_migratetype(gfp_mask) == MIGRATE_CMA) > : alloc_flags |= ALLOC_CMA; > > then I'd have read straight past it. But it's unclear what's happening > here. If we didn't have to resort to telepathy to understand the > meaning of ALLOC_CMA, this wouldn't be so hard. > > > +#endif > > /* Compact each zone in the list */ > > for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, > > nodemask) { > > @@ -889,7 +894,8 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist, > > rc = max(status, rc); > > > > /* If a normal allocation would succeed, stop compacting */ > > - if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0)) > > + if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, > > + alloc_flags)) > > break; > > } > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 287f79d..5985cbf 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1519,19 +1519,6 @@ failed: > > return NULL; > > } > > > > -/* The ALLOC_WMARK bits are used as an index to zone->watermark */ > > -#define ALLOC_WMARK_MIN WMARK_MIN > > -#define ALLOC_WMARK_LOW WMARK_LOW > > -#define ALLOC_WMARK_HIGH WMARK_HIGH > > -#define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */ > > - > > -/* Mask to get the watermark bits */ > > -#define ALLOC_WMARK_MASK (ALLOC_NO_WATERMARKS-1) > > - > > -#define ALLOC_HARDER 0x10 /* try to alloc harder */ > > -#define ALLOC_HIGH 0x20 /* __GFP_HIGH set */ > > -#define ALLOC_CPUSET 0x40 /* check for correct cpuset */ > > Perhaps mm/internal.h wouild have been a better place to move these. > > > #ifdef CONFIG_FAIL_PAGE_ALLOC > > > > static struct { > > @@ -1626,7 +1613,10 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark, > > min -= min / 2; > > if (alloc_flags & ALLOC_HARDER) > > min -= min / 4; > > - > > +#ifdef CONFIG_CMA > > + if (!(alloc_flags & ALLOC_CMA)) > > + free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES); > > Again, the negated test looks weird or just wrong. > > > > Please do something to make this code more understandable. Here is an incremental patch: From: Bartlomiej Zolnierkiewicz Subject: [PATCH] cma: fix watermark checking cleanup Changes: * document ALLOC_CMA * add comment to __zone_watermark_ok() * move ALLOC_* defines to mm/internal.h Cc: Marek Szyprowski Cc: Michal Nazarewicz Cc: Minchan Kim Cc: Mel Gorman Cc: Hugh Dickins Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Kyungmin Park --- include/linux/mmzone.h | 15 --------------- mm/internal.h | 14 ++++++++++++++ mm/page_alloc.c | 1 + 3 files changed, 15 insertions(+), 15 deletions(-) Index: b/include/linux/mmzone.h =================================================================== --- a/include/linux/mmzone.h 2012-09-24 11:09:10.700992708 +0200 +++ b/include/linux/mmzone.h 2012-09-24 11:11:36.520992691 +0200 @@ -231,21 +231,6 @@ enum zone_watermarks { #define low_wmark_pages(z) (z->watermark[WMARK_LOW]) #define high_wmark_pages(z) (z->watermark[WMARK_HIGH]) -/* The ALLOC_WMARK bits are used as an index to zone->watermark */ -#define ALLOC_WMARK_MIN WMARK_MIN -#define ALLOC_WMARK_LOW WMARK_LOW -#define ALLOC_WMARK_HIGH WMARK_HIGH -#define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */ - -/* Mask to get the watermark bits */ -#define ALLOC_WMARK_MASK (ALLOC_NO_WATERMARKS-1) - -#define ALLOC_HARDER 0x10 /* try to alloc harder */ -#define ALLOC_HIGH 0x20 /* __GFP_HIGH set */ -#define ALLOC_CPUSET 0x40 /* check for correct cpuset */ - -#define ALLOC_CMA 0x80 - struct per_cpu_pages { int count; /* number of pages in the list */ int high; /* high watermark, emptying needed */ Index: b/mm/internal.h =================================================================== --- a/mm/internal.h 2012-09-24 11:10:04.848992709 +0200 +++ b/mm/internal.h 2012-09-24 11:11:39.972992691 +0200 @@ -356,3 +356,17 @@ extern unsigned long vm_mmap_pgoff(struc unsigned long, unsigned long); extern void set_pageblock_order(void); + +/* The ALLOC_WMARK bits are used as an index to zone->watermark */ +#define ALLOC_WMARK_MIN WMARK_MIN +#define ALLOC_WMARK_LOW WMARK_LOW +#define ALLOC_WMARK_HIGH WMARK_HIGH +#define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */ + +/* Mask to get the watermark bits */ +#define ALLOC_WMARK_MASK (ALLOC_NO_WATERMARKS-1) + +#define ALLOC_HARDER 0x10 /* try to alloc harder */ +#define ALLOC_HIGH 0x20 /* __GFP_HIGH set */ +#define ALLOC_CPUSET 0x40 /* check for correct cpuset */ +#define ALLOC_CMA 0x80 /* allow allocations from CMA areas */ Index: b/mm/page_alloc.c =================================================================== --- a/mm/page_alloc.c 2012-09-24 11:12:22.212992717 +0200 +++ b/mm/page_alloc.c 2012-09-24 11:15:28.212992661 +0200 @@ -1614,6 +1614,7 @@ static bool __zone_watermark_ok(struct z if (alloc_flags & ALLOC_HARDER) min -= min / 4; #ifdef CONFIG_CMA + /* If allocation can't use CMA areas don't use free CMA pages */ if (!(alloc_flags & ALLOC_CMA)) free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES); #endif -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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