Messages in this thread | | | Date | Thu, 16 Jun 2011 17:45:37 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [GIT PULL] Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex |
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On Fri, Jun 17, 2011 at 12:58:03AM +0200, Ingo Molnar wrote: > > * Andi Kleen <ak@linux.intel.com> 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 periods.
Thanx, Paul
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