+ mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority.patch added to -mm tree

+ mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority.patch added to -mm tree

[akpm]

The patch titled
     mm: vmscan: do not writeback filesystem pages in kswapd except in high priority
has been added to the -mm tree.  Its filename is
     mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority.patch

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------------------------------------------------------
Subject: mm: vmscan: do not writeback filesystem pages in kswapd except in high priority
From: Mel Gorman <mgorman@suse.de>

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 <>
---

 mm/vmscan.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff -puN mm/vmscan.c~mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority
+++ a/mm/vmscan.c
@@ -751,7 +751,8 @@ static noinline_for_stack void free_page
  */
 static unsigned long shrink_page_list(struct list_head *page_list,
 				      struct zone *zone,
-				      struct scan_control *sc)
+				      struct scan_control *sc,
+				      int priority)
 {
 	LIST_HEAD(ret_pages);
 	LIST_HEAD(free_pages);
@@ -857,9 +858,11 @@ static unsigned long shrink_page_list(st
 
 			/*
 			 * Only kswapd can writeback filesystem pages to
-			 * avoid risk of stack overflow
+			 * avoid risk of stack overflow but do not writeback
+			 * unless under significant pressure.
 			 */
-			if (page_is_file_cache(page) && !current_is_kswapd()) {
+			if (page_is_file_cache(page) &&
+					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
 				inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
 				goto keep_locked;
 			}
@@ -1516,12 +1519,12 @@ shrink_inactive_list(unsigned long nr_to
 
 	spin_unlock_irq(&zone->lru_lock);
 
-	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
+	nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority);
 
 	/* Check if we should syncronously wait for writeback */
 	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
 		set_reclaim_mode(priority, sc, true);
-		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
+		nr_reclaimed += shrink_page_list(&page_list, zone, sc, priority);
 	}
 
 	if (!scanning_global_lru(sc))
_

Patches currently in -mm which might be from mgorman@suse.de are

mm-compaction-trivial-clean-up-in-acct_isolated.patch
mm-change-isolate-mode-from-define-to-bitwise-type.patch
mm-compaction-make-isolate_lru_page-filter-aware.patch
mm-zone_reclaim-make-isolate_lru_page-filter-aware.patch
mm-migration-clean-up-unmap_and_move.patch
mm-page-writebackc-make-determine_dirtyable_memory-static-again.patch
mm-vmscan-do-not-writeback-filesystem-pages-in-direct-reclaim.patch
mm-vmscan-remove-dead-code-related-to-lumpy-reclaim-waiting-on-pages-under-writeback.patch
xfs-warn-if-direct-reclaim-tries-to-writeback-pages.patch
ext4-warn-if-direct-reclaim-tries-to-writeback-pages.patch
mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority.patch
mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback.patch
mm-vmscan-immediately-reclaim-end-of-lru-dirty-pages-when-writeback-completes.patch
hugepages-fix-race-between-hugetlbfs-umount-and-quota-update-checkpatch-fixes.patch