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Commit f84f6e2b0868f198f97a32ba503d6f9f319a249a

Authored by Mel Gorman
Committed by Linus Torvalds
1 parent 966dbde2c2
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

mm: vmscan: do not writeback filesystem pages in kswapd except in high priority 

It is preferable that no dirty pages are dispatched for cleaning from the
page reclaim path.  At normal priorities, this patch prevents kswapd
writing pages.

However, page reclaim does have a requirement that pages be freed in a
particular zone.  If it is failing to make sufficient progress (reclaiming
< SWAP_CLUSTER_MAX at any priority priority), the priority is raised to
scan more pages.  A priority of DEF_PRIORITY - 3 is considered to be the
point where kswapd is getting into trouble reclaiming pages.  If this
priority is reached, kswapd will dispatch pages for writing.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 8 additions and 5 deletions Side-by-side Diff

... ... @@ -750,7 +750,8 @@
750 750 */
751 751 static unsigned long shrink_page_list(struct list_head *page_list,
752 752 struct zone *zone,
753   - struct scan_control *sc)
  753 + struct scan_control *sc,
  754 + int priority)
754 755 {
755 756 LIST_HEAD(ret_pages);
756 757 LIST_HEAD(free_pages);
757 758  
... ... @@ -856,9 +857,11 @@
856 857  
857 858 /*
858 859 * Only kswapd can writeback filesystem pages to
859   - * avoid risk of stack overflow
  860 + * avoid risk of stack overflow but do not writeback
  861 + * unless under significant pressure.
860 862 */
861   - if (page_is_file_cache(page) && !current_is_kswapd()) {
  863 + if (page_is_file_cache(page) &&
  864 + (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
862 865 inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
863 866 goto keep_locked;
864 867 }
865 868  
... ... @@ -1509,12 +1512,12 @@
1509 1512  
1510 1513 spin_unlock_irq(&zone->lru_lock);
1511 1514  
1512   - nr_reclaimed = shrink_page_list(&page_list, zone, sc);
  1515 + nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority);
1513 1516  
1514 1517 /* Check if we should syncronously wait for writeback */
1515 1518 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1516 1519 set_reclaim_mode(priority, sc, true);
1517   - nr_reclaimed += shrink_page_list(&page_list, zone, sc);
  1520 + nr_reclaimed += shrink_page_list(&page_list, zone, sc, priority);
1518 1521 }
1519 1522  
1520 1523 local_irq_disable();