From 47a133339c332f9f8e155c70f5da401aded69948 Mon Sep 17 00:00:00 2001 From: Fengguang Wu Date: Wed, 21 Mar 2012 16:34:09 -0700 Subject: [PATCH] mm: use global_dirty_limit in throttle_vm_writeout() When starting a memory hog task, a desktop box w/o swap is found to go unresponsive for a long time. It's solely caused by lots of congestion waits in throttle_vm_writeout(): gnome-system-mo-4201 553.073384: congestion_wait: throttle_vm_writeout+0x70/0x7f shrink_mem_cgroup_zone+0x48f/0x4a1 gnome-system-mo-4201 553.073386: writeback_congestion_wait: usec_timeout=100000 usec_delayed=100000 gtali-4237 553.080377: congestion_wait: throttle_vm_writeout+0x70/0x7f shrink_mem_cgroup_zone+0x48f/0x4a1 gtali-4237 553.080378: writeback_congestion_wait: usec_timeout=100000 usec_delayed=100000 Xorg-3483 553.103375: congestion_wait: throttle_vm_writeout+0x70/0x7f shrink_mem_cgroup_zone+0x48f/0x4a1 Xorg-3483 553.103377: writeback_congestion_wait: usec_timeout=100000 usec_delayed=100000 The root cause is, the dirty threshold is knocked down a lot by the memory hog task. Fixed by using global_dirty_limit which decreases gradually on such events and can guarantee we stay above (the also decreasing) nr_dirty in the progress of following down to the new dirty threshold. Signed-off-by: Fengguang Wu Cc: Johannes Weiner Cc: Jan Kara Cc: Greg Thelen Cc: Ying Han Cc: KAMEZAWA Hiroyuki Reviewed-by: Rik van Riel Cc: Mel Gorman Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page-writeback.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 363ba7082ef5..3fc261705b1e 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1472,6 +1472,7 @@ void throttle_vm_writeout(gfp_t gfp_mask) for ( ; ; ) { global_dirty_limits(&background_thresh, &dirty_thresh); + dirty_thresh = hard_dirty_limit(dirty_thresh); /* * Boost the allowable dirty threshold a bit for page -- 2.20.1