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    SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
    Stephan von Krawczynski wrote:
    >
    > On Mon, 14 Jan 2002 02:04:56 -0800
    > Andrew Morton <akpm@zip.com.au> wrote:
    >
    > > Stephan von Krawczynski wrote:
    > > >
    > > > ...
    > > > Unfortunately me have neither of those. This would mean I cannot benefit
    > from> > _these_ patches, but instead would need _others_
    > [...]
    > >
    > > In 3c59x.c, probably the biggest problem will be the call to issue_and_wait()
    > > in boomerang_start_xmit(). On a LAN which is experiencing heavy collision
    > rates> this can take as long as 2,000 PCI cycles (it's quite rare, and possibly
    > an> erratum). It is called under at least two spinlocks.
    > >
    > > In via-rhine, wait_for_reset() can busywait for up to ten milliseconds.
    > > via_rhine_tx_timeout() calls it from under a spinlock.
    > >
    > > In eepro100.c, wait_for_cmd_done() can busywait for one millisecond
    > > and is called multiple times under spinlock.
    >
    > Did I get that right, as long as spinlocked no sense in conditional_schedule()
    > ?
    >
    > > Preemption will help _some_ of this, but by no means all, or enough.
    >
    > Maybe we should really try to shorten the lock-times _first_. You mentioned a
    > way to find the bad guys?

    Apply the preempt patch and then the preempt-stats patch. Follow
    instructions that come with the stats patch. It will report on the
    longest preempt disable times since the last report. You need to
    provide a load that will exercise the bad code, but it will tell you
    which, where, and how bad. Note: it measures preempt off time, NOT how
    long it took to get to some task, i.e. it does not depend on requesting
    preemption at the worst possible time.
    --
    George george@mvista.com
    High-res-timers: http://sourceforge.net/projects/high-res-timers/
    Real time sched: http://sourceforge.net/projects/rtsched/
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