From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 319F76B002C for ; Fri, 2 Mar 2012 01:14:54 -0500 (EST) Date: Fri, 2 Mar 2012 14:14:51 +0800 From: Fengguang Wu Subject: [PATCH] mm: use global_dirty_limit in throttle_vm_writeout() Message-ID: <20120302061451.GA6468@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Johannes Weiner , Jan Kara , Greg Thelen , Ying Han , KAMEZAWA Hiroyuki , Rik van Riel , Mel Gorman , Minchan Kim , Linux Memory Management List , LKML 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 --- 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org