lkml.org 
[lkml]   [2012]   [Mar]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
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@intel.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

\
 
 \ /
  Last update: 2012-03-02 07:17    [W:0.051 / U:2.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site