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    SubjectRe: [PATCH RFC] smt nice introduces significant lock contention
    Date
    On Friday 02 June 2006 18:28, Nick Piggin wrote:
    > Con Kolivas wrote:
    > > On Friday 02 June 2006 17:53, Nick Piggin wrote:
    > >>This is a small micro-optimisation / cleanup we can do after
    > >>smtnice gets converted to use trylocks. Might result in a little
    > >>less cacheline footprint in some cases.
    > >
    > > It's only dependent_sleeper that is being converted in these patches. The
    > > wake_sleeping_dependent component still locks all runqueues and needs to
    >
    > Oh I missed that.
    >
    > > succeed in order to ensure a task doesn't keep sleeping indefinitely.
    > > That
    >
    > Let's make it use trylocks as well. wake_priority_sleeper should ensure
    > things don't sleep forever I think? We should be optimising for the most
    > common case, and in many workloads, the runqueue does go idle frequently.

    wake_priority_sleeper is only called per tick which can be 10ms at 100HZ. I
    don't think that's fast enough. It could even be possible for a lower
    priority task to always just miss the wakeup if it's (very) unlucky.

    --
    -ck
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