On Mon, Jul 22, 2013 at 01:51:52PM +0100, Christoffer Dall wrote: > On 22 July 2013 10:53, Raghavendra KT <raghavendra.kt.linux@xxxxxxxxx> wrote: > > On Fri, Jul 19, 2013 at 7:23 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > >> So far, when a guest executes WFE (like when waiting for a spinlock > >> to become unlocked), we don't do a thing and let it run uninterrupted. > >> > >> Another option is to trap a blocking WFE and offer the opportunity > >> to the scheduler to switch to another task, potentially giving the > >> vcpu holding the spinlock a chance to run sooner. > >> > > > > Idea looks to be correct from my experiments on x86. It does bring some > > percentage of benefits in overcommitted guests. Infact, > > > > https://lkml.org/lkml/2013/7/22/41 tries to do the same thing for x86. > > (this results in using ple handler heuristics in vcpu_block pach). > > What about the adverse effect in the non-overcommitted case? You might hope to reduce overall system latency, in the same way that PREEMPT kernels implement spin_lock in terms of spin_trylock. Marc might have some ideas about the practical performance of this, but he's currently on holiday and (assumedly) not reading the list! Will -- 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
