Messages in this thread |  | | | From | KOSAKI Motohiro <> | | Subject | Re: [PATCH 5/8] Use io_schedule() instead schedule() | | Date | Tue, 15 Dec 2009 09:56:49 +0900 (JST) |
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> On Mon, 14 Dec 2009 21:30:54 +0900 (JST) > KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote: > > > All task sleeping point in vmscan (e.g. congestion_wait) use > > io_schedule. then shrink_zone_begin use it too. > > > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > > --- > > mm/vmscan.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 3562a2d..0880668 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1624,7 +1624,7 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc) > > max_zone_concurrent_reclaimers) > > break; > > > > - schedule(); > > + io_schedule(); > > Hmm. We have many cond_resched which is not io_schedule in vmscan.c.
cond_resched don't mean sleep on wait queue. it's similar to yield.
> In addition, if system doesn't have swap device space and out of page cache > due to heavy memory pressue, VM might scan & drop pages until priority is zero > or zone is unreclaimable. > > I think it would be not a IO wait.
two point. 1. For long time, Administrator usually watch iowait% at heavy memory pressure. I don't hope change this without reasonable reason. 2. iowait makes scheduler bonus a bit, vmscan task should have many time slice than memory consume task. it improve VM stabilization.
but I agree the benefit isn't so big. if we have reasonable reason, I don't oppose use schedule().
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