On Wed, Jul 30, 2014 at 03:51:22PM +0200, Paolo Bonzini wrote: > Il 30/07/2014 13:39, Ming Lei ha scritto: > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > > index a60104c..943e72f 100644 > > --- a/include/hw/virtio/virtio.h > > +++ b/include/hw/virtio/virtio.h > > @@ -84,12 +84,17 @@ typedef struct VirtQueue VirtQueue; > > typedef struct VirtQueueElement > > { > > unsigned int index; > > + unsigned int num; > > unsigned int out_num; > > unsigned int in_num; > > - hwaddr in_addr[VIRTQUEUE_MAX_SIZE]; > > - hwaddr out_addr[VIRTQUEUE_MAX_SIZE]; > > - struct iovec in_sg[VIRTQUEUE_MAX_SIZE]; > > - struct iovec out_sg[VIRTQUEUE_MAX_SIZE]; > > + > > + hwaddr *in_addr; > > + hwaddr *out_addr; > > + struct iovec *in_sg; > > + struct iovec *out_sg; > > + > > + hwaddr addr[VIRTQUEUE_MAX_SIZE]; > > + struct iovec sg[VIRTQUEUE_MAX_SIZE]; > > } VirtQueueElement; > > > > #define VIRTIO_PCI_QUEUE_MAX 64 > > -- > > since addr and sg aren't used directly, allocate them flexibly like > > char *p; > VirtQueueElement *elem; > total_size = ROUND_UP(sizeof(struct VirtQueueElement), > __alignof__(elem->addr[0]); > addr_offset = total_size; > total_size = ROUND_UP(total_size + num * sizeof(elem->addr[0]), > __alignof__(elem->sg[0])); > sg_offset = total_size; > total_size += num * sizeof(elem->sg[0]); > > elem = p = g_slice_alloc(total_size); > elem->size = total_size; > elem->in_addr = p + addr_offset; > elem->out_addr = elem->in_addr + in_num; > elem->in_sg = p + sg_offset; > elem->out_sg = elem->in_sg + in_num; > > ... > > g_slice_free1(elem->size, elem); > > The small size will help glib do slab-style allocation and should remove > the need for an object pool. > > Paolo
As long as you relying on this, why not allocate in_sg/out_sg separately? In any case, a bunch of code needs to be audited to make sure no one assumes we can always stick VIRTQUEUE_MAX_SIZE there. But what really worries me is this is an optimization patch without any numbers accompanying it. I would say split this out from your virtio blk work, work on this separately. -- MST