Messages in this thread | | | Date | Fri, 28 Aug 2009 21:00:25 +0900 | Subject | Re: [PATCH 1/2] page-allocator: Split per-cpu list into one-list-per-migrate-type | From | Minchan Kim <> |
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On Fri, Aug 28, 2009 at 8:52 PM, Minchan Kim<minchan.kim@gmail.com> wrote: > Hi, Mel. > > On Fri, 28 Aug 2009 09:44:26 +0100 > Mel Gorman <mel@csn.ul.ie> wrote: > >> Currently the per-cpu page allocator searches the PCP list for pages of the >> correct migrate-type to reduce the possibility of pages being inappropriate >> placed from a fragmentation perspective. This search is potentially expensive >> in a fast-path and undesirable. Splitting the per-cpu list into multiple >> lists increases the size of a per-cpu structure and this was potentially >> a major problem at the time the search was introduced. These problem has >> been mitigated as now only the necessary number of structures is allocated >> for the running system. >> >> This patch replaces a list search in the per-cpu allocator with one list per >> migrate type. The potential snag with this approach is when bulk freeing >> pages. We round-robin free pages based on migrate type which has little >> bearing on the cache hotness of the page and potentially checks empty lists >> repeatedly in the event the majority of PCP pages are of one type. >> >> Signed-off-by: Mel Gorman <mel@csn.ul.ie> >> Acked-by: Nick Piggin <npiggin@suse.de> >> --- >> include/linux/mmzone.h | 5 ++- >> mm/page_alloc.c | 106 ++++++++++++++++++++++++++--------------------- >> 2 files changed, 63 insertions(+), 48 deletions(-) >> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index 008cdcd..045348f 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -38,6 +38,7 @@ >> #define MIGRATE_UNMOVABLE 0 >> #define MIGRATE_RECLAIMABLE 1 >> #define MIGRATE_MOVABLE 2 >> +#define MIGRATE_PCPTYPES 3 /* the number of types on the pcp lists */ >> #define MIGRATE_RESERVE 3 >> #define MIGRATE_ISOLATE 4 /* can't allocate from here */ >> #define MIGRATE_TYPES 5 >> @@ -169,7 +170,9 @@ struct per_cpu_pages { >> int count; /* number of pages in the list */ >> int high; /* high watermark, emptying needed */ >> int batch; /* chunk size for buddy add/remove */ >> - struct list_head list; /* the list of pages */ >> + >> + /* Lists of pages, one per migrate type stored on the pcp-lists */ >> + struct list_head lists[MIGRATE_PCPTYPES]; >> }; >> >> struct per_cpu_pageset { >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index ac3afe1..65eedb5 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -522,7 +522,7 @@ static inline int free_pages_check(struct page *page) >> } >> >> /* >> - * Frees a list of pages. >> + * Frees a number of pages from the PCP lists >> * Assumes all pages on list are in same zone, and of same order. >> * count is the number of pages to free. >> * >> @@ -532,23 +532,36 @@ static inline int free_pages_check(struct page *page) >> * And clear the zone's pages_scanned counter, to hold off the "all pages are >> * pinned" detection logic. >> */ >> -static void free_pages_bulk(struct zone *zone, int count, >> - struct list_head *list, int order) >> +static void free_pcppages_bulk(struct zone *zone, int count, >> + struct per_cpu_pages *pcp) >> { >> + int migratetype = 0; >> + > > How about caching the last sucess migratetype > with 'per_cpu_pages->last_alloc_type'? ^^^^ free > I think it could prevent a litte spinning empty list.
Anyway, Ignore me. I didn't see your next patch.
-- Kind regards, Minchan Kim -- 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/
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