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    SubjectRe: Default zone_reclaim_mode = 1 on NUMA kernel is bad for file/email/web servers
    On Mon, 27 Sep 2010 11:04:54 +0900 (JST)
    KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

    > > On Thu, 16 Sep 2010 19:01:32 +0900 (JST)
    > > KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
    > >
    > > > Yes, sadly intel motherboard turn on zone_reclaim_mode by default. and
    > > > current zone_reclaim_mode doesn't fit file/web server usecase ;-)
    > > >
    > > > So, I've created new proof concept patch. This doesn't disable zone_reclaim
    > > > at all. Instead, distinguish for file cache and for anon allocation and
    > > > only file cache doesn't use zone-reclaim.
    > > >
    > > > That said, high-end hpc user often turn on cpuset.memory_spread_page and
    > > > they avoid this issue. But, why don't we consider avoid it by default?
    > > >
    > > >
    > > > Rob, I wonder if following patch help you. Could you please try it?
    > > >
    > > >
    > > > Subject: [RFC] vmscan: file cache doesn't use zone_reclaim by default
    > > >
    > >
    > > Hm, can't we use migration of file caches rather than pageout in
    > > zone_reclaim_mode ? Doent' it fix anything ?
    >
    > Doesn't.
    >
    > Two problem. 1) Migration makes copy. then it's slower than zone_reclaim=0
    > 2) Migration is only effective if target node has much free pages. but it
    > is not generic assumption.
    >
    > For this case, zone_reclaim_mode=0 is best. my patch works as second best.
    > your one works as third.
    >

    Hmm. I'm not sure whether it's "slower" or not. And Migraion doesn't
    assume target node because it can use zonelist fallback.

    I'm just has concerns that kicked-out pages will be paged-in soon.

    But ok, maybe complicated.

    Thanks,
    -Kame



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