On Mon, Jul 13, 2009 at 05:43:15PM +0300, Michael S. Tsirkin wrote: > On Mon, Jul 13, 2009 at 05:33:12PM +0300, Gleb Natapov wrote: > > On Mon, Jul 13, 2009 at 05:21:48PM +0300, Michael S. Tsirkin wrote: > > > On Mon, Jul 13, 2009 at 04:58:58PM +0300, Gleb Natapov wrote: > > > > On Mon, Jul 13, 2009 at 04:53:15PM +0300, Michael S. Tsirkin wrote: > > > > > On Mon, Jul 13, 2009 at 04:28:09PM +0300, Gleb Natapov wrote: > > > > > > On Mon, Jul 13, 2009 at 04:23:36PM +0300, Michael S. Tsirkin wrote: > > > > > > > On Mon, Jul 13, 2009 at 12:12:30PM +0300, Gleb Natapov wrote: > > > > > > > > kvm->irq_lock protects too much stuff, but still fail to protect > > > > > > > > everything it was design to protect (see ack notifiers call in pic). I > > > > > > > > want to make IRQ injection logic use more fine grained locking. > > > > > > > > > > > > > > At least irq routing changes and notifier list changes > > > > > > > do not seem to be involved in irq injection. > > > > > > > So why do we want fine-grained locking there? > > > > > > > > > > > > > When you have one big lock and you want to eliminate it you look at all > > > > > > things it protects and you start introducing different locking for > > > > > > unrelated stuff. This is what this patch series does, so I don't really > > > > > > get you point. > > > > > > > > > > But why do you want to eliminate it? What is the operation that this > > > > > will speed up? Is there a contention issue and which operations > > > > > contend on the lock? > > > > > > > > > Interrupt injection. I want to be able to inject interrupts without the > > > > lock at all. > > > > > > You are talking about the lapic changes below, right? OK. But how do > > > the other changes help, specifically? I'm less familiar with ioapic, but > > > I think irq routing and irq notifier list changes are done off data > > > path. > > > > > irq_routing is accessed on irq injection path, so making in lockless is > > necessary to achieve the goal. Making ack notifiers lockless removes one > > lock from EOI path. > > But this is done with RCU patches, right? > No, not right. Only rcu patch is meaningless since irq injection is still done under irq_lock. Look at the whole series, not each line by itself. -- Gleb. -- 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
