On Tue, Jan 31, 2012 at 02:50:07PM +0100, Peter Zijlstra wrote: > On Tue, 2012-01-31 at 15:47 +0200, Avi Kivity wrote: > > > They really need to return quickly to userspace, and they really need to > > perform some operation between rcu_assign_pointer() and returning, so no. > > Bugger :/ > > > > > > > Compile tested only!! :-) > > > > > > > How much did synchronize_srcu_expedited() regress? Presumably your > > compiler didn't tell you that. > > Nope, quite a lot I figure. > > > Can we get it back to speed by scheduling a work function on all cpus? > > wouldn't that force a quiescent state and allow call_srcu() to fire? > > > > In kvm's use case synchronize_srcu_expedited() is usually called when no > > thread is in a critical section, so we don't have to wait for anything > > except the srcu machinery. > > OK, I'll try and come up with means of making it go fast again ;-) I cannot resist suggesting a kthread to do the call_srcu(), which would allow synchronize_srcu_expedited() to proceed with its current brute-force speed. Thanx, Paul -- 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
