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Message-ID: <20100908132742.GF29263@csn.ul.ie>
Date: Wed, 8 Sep 2010 14:27:42 +0100
From: Mel Gorman <mel@....ul.ie>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
Linux Kernel List <linux-kernel@...r.kernel.org>,
Rik van Riel <riel@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Minchan Kim <minchan.kim@...il.com>,
Andrea Arcangeli <aarcange@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Dave Chinner <david@...morbit.com>,
Chris Mason <chris.mason@...cle.com>,
Christoph Hellwig <hch@....de>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 08/10] vmscan: isolated_lru_pages() stop neighbour
search if neighbour cannot be isolated
On Wed, Sep 08, 2010 at 09:14:04PM +0800, Wu Fengguang wrote:
> On Wed, Sep 08, 2010 at 08:50:44PM +0800, Mel Gorman wrote:
> > On Wed, Sep 08, 2010 at 07:37:34PM +0800, Wu Fengguang wrote:
> > > On Mon, Sep 06, 2010 at 06:47:31PM +0800, Mel Gorman wrote:
> > > > From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > > >
> > > > isolate_lru_pages() does not just isolate LRU tail pages, but also isolate
> > > > neighbour pages of the eviction page. The neighbour search does not stop even
> > > > if neighbours cannot be isolated which is excessive as the lumpy reclaim will
> > > > no longer result in a successful higher order allocation. This patch stops
> > > > the PFN neighbour pages if an isolation fails and moves on to the next block.
> > > >
> > > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > > > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > > > ---
> > > > mm/vmscan.c | 24 ++++++++++++++++--------
> > > > 1 files changed, 16 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > > index 64f9ca5..ff52b46 100644
> > > > --- a/mm/vmscan.c
> > > > +++ b/mm/vmscan.c
> > > > @@ -1047,14 +1047,18 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> > > > continue;
> > > >
> > > > /* Avoid holes within the zone. */
> > > > - if (unlikely(!pfn_valid_within(pfn)))
> > > > + if (unlikely(!pfn_valid_within(pfn))) {
> > > > + nr_lumpy_failed++;
> > > > break;
> > > > + }
> > > >
> > > > cursor_page = pfn_to_page(pfn);
> > > >
> > > > /* Check that we have not crossed a zone boundary. */
> > > > - if (unlikely(page_zone_id(cursor_page) != zone_id))
> > > > - continue;
> > > > + if (unlikely(page_zone_id(cursor_page) != zone_id)) {
> > > > + nr_lumpy_failed++;
> > > > + break;
> > > > + }
> > > >
> > > > /*
> > > > * If we don't have enough swap space, reclaiming of
> > > > @@ -1062,8 +1066,10 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> > > > * pointless.
> > > > */
> > > > if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
> > > > - !PageSwapCache(cursor_page))
> > > > - continue;
> > > > + !PageSwapCache(cursor_page)) {
> > > > + nr_lumpy_failed++;
> > > > + break;
> > > > + }
> > > >
> > > > if (__isolate_lru_page(cursor_page, mode, file) == 0) {
> > > > list_move(&cursor_page->lru, dst);
> > > > @@ -1074,9 +1080,11 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> > > > nr_lumpy_dirty++;
> > > > scan++;
> > > > } else {
> > > > - if (mode == ISOLATE_BOTH &&
> > > > - page_count(cursor_page))
> > > > - nr_lumpy_failed++;
> > > > + /* the page is freed already. */
> > > > + if (!page_count(cursor_page))
> > > > + continue;
> > > > + nr_lumpy_failed++;
> > > > + break;
> > > > }
> > > > }
> > >
> > > The many nr_lumpy_failed++ can be moved here:
> > >
> > > if (pfn < end_pfn)
> > > nr_lumpy_failed++;
> > >
> >
> > Because the break stops the loop iterating, is there an advantage to
> > making it a pfn check instead? I might be misunderstanding your
> > suggestion.
>
> The complete view in my mind is
>
> for (; pfn < end_pfn; pfn++) {
> if (failed 1)
> break;
> if (failed 2)
> break;
> if (failed 3)
> break;
> }
> if (pfn < end_pfn)
> nr_lumpy_failed++;
>
> Sure it just reduces several lines of code :)
>
Fair point. I applied the following patch on top.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 33d27a4..54df972 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1091,18 +1091,14 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
continue;
/* Avoid holes within the zone. */
- if (unlikely(!pfn_valid_within(pfn))) {
- nr_lumpy_failed++;
+ if (unlikely(!pfn_valid_within(pfn)))
break;
- }
cursor_page = pfn_to_page(pfn);
/* Check that we have not crossed a zone boundary. */
- if (unlikely(page_zone_id(cursor_page) != zone_id)) {
- nr_lumpy_failed++;
+ if (unlikely(page_zone_id(cursor_page) != zone_id))
break;
- }
/*
* If we don't have enough swap space, reclaiming of
@@ -1110,10 +1106,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
* pointless.
*/
if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
- !PageSwapCache(cursor_page)) {
- nr_lumpy_failed++;
+ !PageSwapCache(cursor_page))
break;
- }
if (__isolate_lru_page(cursor_page, mode, file) == 0) {
list_move(&cursor_page->lru, dst);
@@ -1127,10 +1121,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
/* the page is freed already. */
if (!page_count(cursor_page))
continue;
- nr_lumpy_failed++;
break;
}
}
+
+ /* If we break out of the loop above, lumpy reclaim failed */
+ if (pfn < end_pfn)
+ nr_lumpy_failed++;
}
*scanned = scan;
--
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