[Intel-gfx] [PATCH] mm: Throttle shrinkers harder

[Chris Wilson]

During testing of i915.ko with working texture sets larger than RAM, we
encounter OOM with plenty of memory still trapped within writeback, e.g:

[   42.386039] active_anon:10134 inactive_anon:1900781 isolated_anon:32
 active_file:33 inactive_file:39 isolated_file:0
 unevictable:0 dirty:0 writeback:337627 unstable:0
 free:11985 slab_reclaimable:9458 slab_unreclaimable:23614
 mapped:41 shmem:1560769 pagetables:1276 bounce:0

If we throttle for writeback following shrink_slab, this gives us time
to wait upon the writeback generated by the i915.ko shinker:

[ 4756.750808] active_anon:24386 inactive_anon:900793 isolated_anon:0
 active_file:23 inactive_file:20 isolated_file:0
 unevictable:0 dirty:0 writeback:0 unstable:0
 free:5550 slab_reclaimable:5184 slab_unreclaimable:4888
 mapped:3 shmem:472393 pagetables:1249 bounce:0

(Sadly though the test is still failing.)

Testcase: igt/gem_tiled_swapping
References: https://bugs.freedesktop.org/show_bug.cgi?id=72742
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Mel Gorman <mgorman at suse.de>
Cc: Michal Hocko <mhocko at suse.cz>
Cc: Rik van Riel <riel at redhat.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Dave Chinner <dchinner at redhat.com>
Cc: Glauber Costa <glommer at openvz.org>
Cc: Hugh Dickins <hughd at google.com>
Cc: linux-mm at kvack.org
---
 mm/vmscan.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a9c74b409681..8c2cb1150d17 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -135,6 +135,10 @@ unsigned long vm_total_pages;	/* The total number of pages which the VM controls
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
+static bool throttle_direct_reclaim(gfp_t gfp_mask,
+				    struct zonelist *zonelist,
+				    nodemask_t *nodemask);
+
 #ifdef CONFIG_MEMCG
 static bool global_reclaim(struct scan_control *sc)
 {
@@ -1521,7 +1525,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 	 * of pages under pages flagged for immediate reclaim and stall if any
 	 * are encountered in the nr_immediate check below.
 	 */
-	if (nr_writeback && nr_writeback == nr_taken)
+	if (nr_writeback > nr_taken / 2)
 		zone_set_flag(zone, ZONE_WRITEBACK);
 
 	/*
@@ -2465,6 +2469,12 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 						WB_REASON_TRY_TO_FREE_PAGES);
 			sc->may_writepage = 1;
 		}
+
+		if (global_reclaim(sc) &&
+		    throttle_direct_reclaim(sc->gfp_mask,
+					    zonelist,
+					    sc->nodemask))
+			aborted_reclaim = true;
 	} while (--sc->priority >= 0 && !aborted_reclaim);
 
 out:
-- 
1.9.1