On Tue, 8 May 2012 13:18:39 +0300, "Michael S. Tsirkin" <[email protected]> wrote: > On Tue, May 08, 2012 at 11:45:55AM +0200, Paolo Bonzini wrote: > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -76,8 +76,6 @@ > > > > struct vring_virtqueue > > { > > - struct virtqueue vq; > > - > > /* Actual memory layout for this queue */ > > struct vring vring; > > > > @@ -106,6 +104,9 @@ struct vring_virtqueue > > /* How to notify other side. FIXME: commonalize hcalls! */ > > void (*notify)(struct virtqueue *vq); > > > > + /* Tokens for callbacks. */ > > + void **data; > > + > > #ifdef DEBUG > > /* They're supposed to lock for us. */ > > unsigned int in_use; > > @@ -115,8 +116,9 @@ struct vring_virtqueue > > ktime_t last_add_time; > > #endif > > > > - /* Tokens for callbacks. */ > > - void *data[]; > > + struct virtqueue vq; > > + > > + /* Bus-specific virtqueue data goes here. */ > > }; > > > > #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq) > > > This moves the data out of line and the bus specific stuff inline. > But bus accesses only happen on io and interrupt which are already > slow, while data accesses happen on fast path. > > >From that POV this looks like a wrong thing to do.
(Resend to all) Most of it was on a different cacheline anyway though, so it's probably not measurable. We avoid the pci_vq->vq indirection, but add the vq->data indirection. I share your discomfort with the offset arg method, too. So unless benchmarks show otherwise, let's do it the vanilla way? I think that making vring_virtqueue public looks like the way to go, too. Of course, a nice series would be great as well :) Thanks! Rusty. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
