Messages in this thread Patch in this message | | | Date | Thu, 13 Sep 2012 08:58:55 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH] mm: cma: Discard clean pages during contiguous allocation instead of migration |
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On Wed, Sep 12, 2012 at 01:07:32PM -0700, Andrew Morton wrote: > On Tue, 11 Sep 2012 09:41:52 +0900 > Minchan Kim <minchan@kernel.org> wrote: > > > This patch drops clean cache pages instead of migration during > > alloc_contig_range() to minimise allocation latency by reducing the amount > > of migration is necessary. It's useful for CMA because latency of migration > > is more important than evicting the background processes working set. > > In addition, as pages are reclaimed then fewer free pages for migration > > targets are required so it avoids memory reclaiming to get free pages, > > which is a contributory factor to increased latency. > > > > * from v1 > > * drop migrate_mode_t > > * add reclaim_clean_pages_from_list instad of MIGRATE_DISCARD support - Mel > > > > I measured elapsed time of __alloc_contig_migrate_range which migrates > > 10M in 40M movable zone in QEMU machine. > > > > Before - 146ms, After - 7ms > > > > ... > > > > @@ -758,7 +760,9 @@ static unsigned long shrink_page_list(struct list_head *page_list, > > wait_on_page_writeback(page); > > } > > > > - references = page_check_references(page, sc); > > + if (!force_reclaim) > > + references = page_check_references(page, sc); > > grumble. Could we please document `enum page_references' and > page_check_references()? > > And the `force_reclaim' arg could do with some documentation. It only > forces reclaim under certain circumstances. They should be described, > and a reson should be provided.
I will give it a shot by another patch.
> > Why didn't this patch use PAGEREF_RECLAIM_CLEAN? It is possible for > someone to dirty one of these pages after we tested its cleanness and > we'll then go off and write it out, but we won't be reclaiming it?
Absolutely. Thanks Andrew!
Here it goes.
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From 90022feb9ecf8e9a4efba7cbf49d7cead777020f Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@kernel.org> Date: Thu, 13 Sep 2012 08:45:58 +0900 Subject: [PATCH] mm: cma: reclaim only clean pages
It is possible for pages to be dirty after the check in reclaim_clean_pages_from_list so that it ends up paging out the pages, which is never what we want for speed up.
This patch fixes it.
Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index f8f56f8..1ee4b69 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -694,7 +694,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, struct address_space *mapping; struct page *page; int may_enter_fs; - enum page_references references = PAGEREF_RECLAIM; + enum page_references references = PAGEREF_RECLAIM_CLEAN; cond_resched(); -- 1.7.9.5 -- Kind regards, Minchan Kim
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