Messages in this thread |  | | Date | Wed, 21 Mar 2012 09:43:44 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH] mm: use global_dirty_limit in throttle_vm_writeout() |
| |
Hi Wu,
Sorry for late response. I have a question.
On Fri, Mar 02, 2012 at 02:14:51PM +0800, Fengguang Wu wrote: > 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
AFAIUC, memory hog task, you mean it consumes lots of anon pages, not file-backed pages. So global_dirty_limits would get small available_memory by global_reclaimable_pages so that it ends up dirty threshold is knocked down.
Could you confirm my understanding?
Thanks.
> 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
|  |