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Date: Fri, 2 Mar 2012 14:14:51 +0800 From: Fengguang Wu <fengguang.wu@...el.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>, Greg Thelen <gthelen@...gle.com>, Ying Han <yinghan@...gle.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan.kim@...il.com>, Linux Memory Management List <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org> 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 <fengguang.wu@...el.com> --- mm/page-writeback.c | 1 + 1 file changed, 1 insertion(+) --- linux.orig/mm/page-writeback.c 2012-03-02 14:05:01.633763187 +0800 +++ linux/mm/page-writeback.c 2012-03-02 14:11:52.929772962 +0800 @@ -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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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