Messages in this thread Patch in this message | | | Date | Fri, 2 Mar 2012 14:14:51 +0800 | From | Fengguang Wu <> | Subject | [PATCH] mm: use global_dirty_limit in throttle_vm_writeout() |
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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
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