On Tue, Jun 23, 2009 at 11:21:53AM -0400, Gregory Haskins wrote: > Michael S. Tsirkin wrote: > > Remove in_range from kvm_io_device and ask read/write callbacks, if > > supplied, to perform range checks internally. This allows aliasing > > (mostly for in-kernel virtio), as well as better error handling by > > making it possible to pass errors up to userspace. And it's enough to > > look at the diffstat to see that it's a better API anyway. > > > > While we are at it, document locking rules for kvm_io_device. > > > > Sorry, not trying to be a PITA, but I liked your last suggestion better. :( > > I am thinking forward to when we want to use something smarter than a > linear search (like rbtree/radix) for scaling the number of "devices" > (really, virtio-rings) that we support. in_range is broken for this anyway: you need more than a boolean predicate to implement rbtree/radix > The current device-count > target is 512, which we will begin to rapidly consume as the in-kernel > virtio work progresses. That's a large number. I had in mind more like 4 virtio devices, for starters: 1 for each virtqueue in net and block. > This proposed approach forces us into a > potential O(256) algorithm in the hotpath (all MMIO/PIO exits will hit > this, not just in-kernel users). How would you address this? Two ideas that come to mind: - add addr/len fields to devices, use these to speed up lookup - add a small cache that can be scanned first In both cases, you first do a fast lookup, ask the device whether it wants the transaction, then resort to linear scan if not -- MST -- 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
