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    SubjectRe: [GIT PULL] Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex
    On Fri, Jun 17, 2011 at 12:58:03AM +0200, Ingo Molnar wrote:
    > * Andi Kleen <> wrote:
    > > > There's a crazy solution for that: the idle thread could process
    > > > RCU callbacks carefully, as if it was running user-space code.
    > >
    > > In Ben's kernel NFS server case the system may not be idle.
    > An always-100%-busy NFS server is very unlikely, but even in the
    > hypothetical case a kernel NFS server is really performing system
    > calls from a kernel thread in essence. If it doesn't do it explicitly
    > then its main loop can easily include a "check RCU callbacks" call.

    As long as they make sure to call it in a clean environment: no locks
    held and so on. But I am a bit worried about the possibility of someone
    forgetting to put one of these where it is needed -- it would work just
    fine for most workloads, but could fail only for rare workloads.

    That said, invoking RCU core/callback processing from the scheduler
    context certainly sounds like an interesting way to speed up grace

    Thanx, Paul

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