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    SubjectRe: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)

    * Peter Zijlstra <peterz@infradead.org> wrote:

    > On Tue, 2007-07-31 at 01:46 +0200, Kasper Sandberg wrote:
    >
    > > could perhaps be filesystem related, i have my maildir(extremely
    > > large) on reiserfs, and /home on xfs. what my mail client will do is
    > > download mail, spamasassin it(loading database from home), then it
    > > will put to imap server placing it on reiserfs, and then a "local"
    > > copy in my home.
    >
    > Ooh, do you perchance have PREEMPT_BKL=y?
    >
    > If so, try on another filesystem than reiserfs (or disable
    > PREEMPT_BKL, but that is obviously the lesser of the two choices).
    >
    > Ingo traced a 1+ second latency at my end to BKL priority inversion
    > between tty and reiserfs.

    ah, indeed, that makes quite a bit of sense. Almost all of the Reiser3
    code runs under the BKL, and the only other major kernel infrastructure
    that has BKL dependencies is the TTY code. Kasper, as a debugging
    matter, could you try to move that spamassassin workload off into a
    non-Reiser3 filesystem and/or disable PREEMPT_BKL? If that makes a
    noticeable difference (for the better ;) then we can continue figuring
    out what's happening exactly.

    Ingo
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