Messages in this thread | | | Subject | Re: [PATCH 4/8] Use prepare_to_wait_exclusive() instead prepare_to_wait() | From | Mike Galbraith <> | Date | Tue, 15 Dec 2009 19:43:30 +0100 |
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On Tue, 2009-12-15 at 09:58 -0500, Rik van Riel wrote: > On 12/15/2009 12:32 AM, Mike Galbraith wrote: > > On Tue, 2009-12-15 at 09:45 +0900, KOSAKI Motohiro wrote: > >>> On 12/14/2009 07:30 AM, KOSAKI Motohiro wrote: > >>>> if we don't use exclusive queue, wake_up() function wake _all_ waited > >>>> task. This is simply cpu wasting. > >>>> > >>>> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com> > >>> > >>>> if (zone_watermark_ok(zone, sc->order, low_wmark_pages(zone), > >>>> 0, 0)) { > >>>> - wake_up(wq); > >>>> + wake_up_all(wq); > >>>> finish_wait(wq,&wait); > >>>> sc->nr_reclaimed += sc->nr_to_reclaim; > >>>> return -ERESTARTSYS; > >>> > >>> I believe we want to wake the processes up one at a time > >>> here. > > >> Actually, wake_up() and wake_up_all() aren't different so much. > >> Although we use wake_up(), the task wake up next task before > >> try to alloate memory. then, it's similar to wake_up_all(). > > That is a good point. Maybe processes need to wait a little > in this if() condition, before the wake_up(). That would give > the previous process a chance to allocate memory and we can > avoid waking up too many processes.
Pondering, I think I'd at least wake NR_CPUS. If there's not enough to go round, oh darn, but if there is, you have full utilization quicker.
$.02.
-Mike
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