Messages in this thread | | | Date | Wed, 26 Sep 2012 15:39:05 +0200 | From | Andrew Jones <> | Subject | Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler |
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On Wed, Sep 26, 2012 at 03:26:11PM +0200, Peter Zijlstra wrote: > On Wed, 2012-09-26 at 15:20 +0200, Andrew Jones wrote: > > Wouldn't a clean solution be to promote a task's scheduler > > class to the spinner class when we PLE (or come from some special > > syscall > > for userspace spinlocks?)? > > Userspace spinlocks are typically employed to avoid syscalls..
I'm guessing there could be a slow path - spin N times and then give up and yield.
> > > That class would be higher priority than the > > fair class and would schedule in FIFO order, but it would only run its > > tasks for short periods before switching. > > Since lock hold times aren't limited, esp. for things like userspace > 'spin' locks, you've got a very good denial of service / opportunity for > abuse right there.
Maybe add some throttling to avoid overuse/maliciousness?
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