+ mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch added to -mm tree

+ mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm, vmscan: account for skipped pages as a partial scan
has been added to the -mm tree.  Its filename is
     mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch

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------------------------------------------------------
From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm, vmscan: account for skipped pages as a partial scan

Page reclaim determines whether a pgdat is unreclaimable by examining how
many pages have been scanned since a page was freed and comparing that to
the LRU sizes.  Skipped pages are not reclaim candidates but contribute to
scanned.  This can prematurely mark a pgdat as unreclaimable and trigger
an OOM kill.

This patch accounts for skipped pages as a partial scan so that an
unreclaimable pgdat will still be marked as such but by scaling the cost
of a skip, it'll avoid the pgdat being marked prematurely.

Link: http://lkml.kernel.org/r/1469110261-7365-6-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff -puN mm/vmscan.c~mm-vmscan-account-for-skipped-pages-as-a-partial-scan mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-account-for-skipped-pages-as-a-partial-scan
+++ a/mm/vmscan.c
@@ -1424,7 +1424,7 @@ static unsigned long isolate_lru_pages(u
 	LIST_HEAD(pages_skipped);
 
 	for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
-					!list_empty(src); scan++) {
+					!list_empty(src);) {
 		struct page *page;
 
 		page = lru_to_page(src);
@@ -1438,6 +1438,12 @@ static unsigned long isolate_lru_pages(u
 			continue;
 		}
 
+		/*
+		 * Account for scanned and skipped separetly to avoid the pgdat
+		 * being prematurely marked unreclaimable by pgdat_reclaimable.
+		 */
+		scan++;
+
 		switch (__isolate_lru_page(page, mode)) {
 		case 0:
 			nr_pages = hpage_nr_pages(page);
@@ -1465,14 +1471,24 @@ static unsigned long isolate_lru_pages(u
 	 */
 	if (!list_empty(&pages_skipped)) {
 		int zid;
+		unsigned long total_skipped = 0;
 
-		list_splice(&pages_skipped, src);
 		for (zid = 0; zid < MAX_NR_ZONES; zid++) {
 			if (!nr_skipped[zid])
 				continue;
 
 			__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
+			total_skipped += nr_skipped[zid];
 		}
+
+		/*
+		 * Account skipped pages as a partial scan as the pgdat may be
+		 * close to unreclaimable. If the LRU list is empty, account
+		 * skipped pages as a full scan.
+		 */
+		scan += list_empty(src) ? total_skipped : total_skipped >> 2;
+
+		list_splice(&pages_skipped, src);
 	}
 	*nr_scanned = scan;
 	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, scan,
_

Patches currently in -mm which might be from mgorman@techsingularity.net are

mm-meminit-remove-early_page_nid_uninitialised.patch
mm-vmstat-add-infrastructure-for-per-node-vmstats.patch
mm-vmscan-move-lru_lock-to-the-node.patch
mm-vmscan-move-lru-lists-to-node.patch
mm-mmzone-clarify-the-usage-of-zone-padding.patch
mm-vmscan-begin-reclaiming-pages-on-a-per-node-basis.patch
mm-vmscan-have-kswapd-only-scan-based-on-the-highest-requested-zone.patch
mm-vmscan-make-kswapd-reclaim-in-terms-of-nodes.patch
mm-vmscan-remove-balance-gap.patch
mm-vmscan-simplify-the-logic-deciding-whether-kswapd-sleeps.patch
mm-vmscan-by-default-have-direct-reclaim-only-shrink-once-per-node.patch
mm-vmscan-remove-duplicate-logic-clearing-node-congestion-and-dirty-state.patch
mm-vmscan-do-not-reclaim-from-kswapd-if-there-is-any-eligible-zone.patch
mm-vmscan-make-shrink_node-decisions-more-node-centric.patch
mm-vmscan-make-shrink_node-decisions-more-node-centric-fix.patch
mm-memcg-move-memcg-limit-enforcement-from-zones-to-nodes.patch
mm-workingset-make-working-set-detection-node-aware.patch
mm-page_alloc-consider-dirtyable-memory-in-terms-of-nodes.patch
mm-move-page-mapped-accounting-to-the-node.patch
mm-rename-nr_anon_pages-to-nr_anon_mapped.patch
mm-move-most-file-based-accounting-to-the-node.patch
mm-move-most-file-based-accounting-to-the-node-fix.patch
mm-move-vmscan-writes-and-file-write-accounting-to-the-node.patch
mm-vmscan-only-wakeup-kswapd-once-per-node-for-the-requested-classzone.patch
mm-page_alloc-wake-kswapd-based-on-the-highest-eligible-zone.patch
mm-convert-zone_reclaim-to-node_reclaim.patch
mm-vmscan-avoid-passing-in-classzone_idx-unnecessarily-to-shrink_node.patch
mm-vmscan-avoid-passing-in-classzone_idx-unnecessarily-to-compaction_ready.patch
mm-vmscan-avoid-passing-in-classzone_idx-unnecessarily-to-compaction_ready-fix.patch
mm-vmscan-avoid-passing-in-remaining-unnecessarily-to-prepare_kswapd_sleep.patch
mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit.patch
mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit-fix.patch
mm-vmscan-add-classzone-information-to-tracepoints.patch
mm-page_alloc-remove-fair-zone-allocation-policy.patch
mm-page_alloc-cache-the-last-node-whose-dirty-limit-is-reached.patch
mm-vmstat-replace-__count_zone_vm_events-with-a-zone-id-equivalent.patch
mm-vmstat-account-per-zone-stalls-and-pages-skipped-during-reclaim.patch
mm-vmstat-account-per-zone-stalls-and-pages-skipped-during-reclaim-fix.patch
mm-vmstat-print-node-based-stats-in-zoneinfo-file.patch
mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries.patch
mm-vmstat-remove-zone-and-node-double-accounting-by-approximating-retries-fix.patch
mm-pagevec-release-reacquire-lru_lock-on-pgdat-change.patch
mm-vmscan-update-all-zone-lru-sizes-before-updating-memcg.patch
mm-vmscan-remove-redundant-check-in-shrink_zones.patch
mm-vmscan-release-reacquire-lru_lock-on-pgdat-change.patch
mm-vmscan-release-reacquire-lru_lock-on-pgdat-change-fix.patch
mm-vmscan-remove-highmem_file_pages.patch
mm-remove-reclaim-and-compaction-retry-approximations.patch
mm-vmscan-account-for-skipped-pages-as-a-partial-scan.patch