On 02/07/2011 07:23 PM, Jan Kiszka wrote:
On 2011-02-07 18:10, Avi Kivity wrote: > On 02/07/2011 06:59 PM, Jan Kiszka wrote: >>> >>> (well, actually, cpufreq_notifier and kvm_arch_hardware_enable are >>> already non preemptible, and the stats code should just go away?) >> >> The stats code is trivial to convert, so it doesn't matter. > > Removal is easier. Is that stat interface no longer used?
It's there for compatibility. I'm itching to remove it. See qemu-kvm.git/kvm/kvm_stat for the only known user, and for the replacement via tracepoints.
Tracepoints have marginally lower overhead when disabled, and somewhat higher overhead when enabled. A disadvantage of tracepoints is that it is harder to associate an event with a vm when that event is triggered by a workqueue, but I don't think it matters in practice (kvm_stat doesn't even provide a per-vm breakdown).
> >> But what about mmu_shrink and its list_move_tail? How is this >> synchronized against kvm_destroy_vm - already today? > > kvm_destroy_vm() takes kvm_lock. If a vm is destroyed before > mmu_shrink(), mmu_shrink() will never see it. If we reach mmu_shrink() > before kvm_destroy_vm(), the latter will wait until mmu_shrink() is done. > Ah, I was confused. Would require some more logic if we wanted to make the loop lock-less, though.
Yes, the usual rcu_read_lock() / grab reference / rcu_read_unlock(). -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
