git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 72853e2991a2702ae93aaf889ac7db743a415dd3 Mon Sep 17 00:00:00 2001
   2 From: Mel Gorman <mel@csn.ul.ie>
   3 Date: Thu, 9 Sep 2010 16:38:16 -0700
   4 Subject: mm: page allocator: update free page counters after pages are placed on the free list
   5
   6 From: Mel Gorman <mel@csn.ul.ie>
   7
   8 commit 72853e2991a2702ae93aaf889ac7db743a415dd3 upstream.
   9
  10 When allocating a page, the system uses NR_FREE_PAGES counters to
  11 determine if watermarks would remain intact after the allocation was made.
  12 This check is made without interrupts disabled or the zone lock held and
  13 so is race-prone by nature.  Unfortunately, when pages are being freed in
  14 batch, the counters are updated before the pages are added on the list.
  15 During this window, the counters are misleading as the pages do not exist
  16 yet.  When under significant pressure on systems with large numbers of
  17 CPUs, it's possible for processes to make progress even though they should
  18 have been stalled.  This is particularly problematic if a number of the
  19 processes are using GFP_ATOMIC as the min watermark can be accidentally
  20 breached and in extreme cases, the system can livelock.
  21
  22 This patch updates the counters after the pages have been added to the
  23 list.  This makes the allocator more cautious with respect to preserving
  24 the watermarks and mitigates livelock possibilities.
  25
  26 [akpm@linux-foundation.org: avoid modifying incoming args]
  27 Signed-off-by: Mel Gorman <mel@csn.ul.ie>
  28 Reviewed-by: Rik van Riel <riel@redhat.com>
  29 Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
  30 Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
  31 Reviewed-by: Christoph Lameter <cl@linux.com>
  32 Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
  33 Acked-by: Johannes Weiner <hannes@cmpxchg.org>
  34 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  35 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  36 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  37
  38 ---
  39  mm/page_alloc.c |    9 +++++----
  40  1 file changed, 5 insertions(+), 4 deletions(-)
  41
  42 --- a/mm/page_alloc.c
  43 +++ b/mm/page_alloc.c
  44 @@ -588,13 +588,13 @@ static void free_pcppages_bulk(struct zo
  45  {
  46         int migratetype = 0;
  47         int batch_free = 0;
  48 +       int to_free = count;
  49
  50         spin_lock(&zone->lock);
  51         zone->all_unreclaimable = 0;
  52         zone->pages_scanned = 0;
  53
  54 -       __mod_zone_page_state(zone, NR_FREE_PAGES, count);
  55 -       while (count) {
  56 +       while (to_free) {
  57                 struct page *page;
  58                 struct list_head *list;
  59
  60 @@ -619,8 +619,9 @@ static void free_pcppages_bulk(struct zo
  61                         /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
  62                         __free_one_page(page, zone, 0, page_private(page));
  63                         trace_mm_page_pcpu_drain(page, 0, page_private(page));
  64 -               } while (--count && --batch_free && !list_empty(list));
  65 +               } while (--to_free && --batch_free && !list_empty(list));
  66         }
  67 +       __mod_zone_page_state(zone, NR_FREE_PAGES, count);
  68         spin_unlock(&zone->lock);
  69  }
  70
  71 @@ -631,8 +632,8 @@ static void free_one_page(struct zone *z
  72         zone->all_unreclaimable = 0;
  73         zone->pages_scanned = 0;
  74
  75 -       __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
  76         __free_one_page(page, zone, order, migratetype);
  77 +       __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
  78         spin_unlock(&zone->lock);
  79  }
  80