This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h | 5 +++++ 2 files changed, 13 insertions(+), 0 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index a882f26..e2e5eb7 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -137,6 +137,13 @@ static int vring_add_indirect(struct vring_virtqueue *vq, return head; } +static bool vring_can_add_buf(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + + return vq->num_free ? 1 : 0; +} + static int vring_add_buf(struct virtqueue *_vq, struct scatterlist sg[], unsigned int out, @@ -350,6 +357,7 @@ EXPORT_SYMBOL_GPL(vring_interrupt); static struct virtqueue_ops vring_vq_ops = { .add_buf = vring_add_buf, .get_buf = vring_get_buf, + .can_add_buf = vring_can_add_buf, .kick = vring_kick, .disable_cb = vring_disable_cb, .enable_cb = vring_enable_cb, diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 4fca4f5..cc0e3aa 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -35,6 +35,9 @@ struct virtqueue { * in_num: the number of sg which are writable (after readable ones) * data: the token identifying the buffer. * Returns 0 or an error. + * @can_add_buf: indicates whether we have a free slot to add a buffer + * vq: the struct virtqueue we're talking about. + * Returns 0 or 1. * @kick: update after add_buf * vq: the struct virtqueue * After one or more add_buf calls, invoke this to kick the other side. @@ -65,6 +68,8 @@ struct virtqueue_ops { unsigned int in_num, void *data); + bool (*can_add_buf)(struct virtqueue *vq); + void (*kick)(struct virtqueue *vq); void *(*get_buf)(struct virtqueue *vq, unsigned int *len); -- 1.6.2.5
Amit Shah
2009-Aug-18 16:01 UTC
[PATCH 2/2] virtio_net: Use can_add_buf to test for enough room to add
Use the can_add_buf virtqueue operation to test if there's room to add another buf to the queue. Saves us one cycle of alloc-add-free if the queue was full. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/net/virtio_net.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 2a6e81d..fd1d628 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -280,7 +280,7 @@ static void try_fill_recv_maxbufs(struct virtnet_info *vi) int num, err, i; sg_init_table(sg, 2+MAX_SKB_FRAGS); - for (;;) { + while (vi->rvq->vq_ops->can_add_buf(vi->rvq)) { struct virtio_net_hdr *hdr; skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN); -- 1.6.2.5
On Wed, 19 Aug 2009 01:31:29 am Amit Shah wrote:> This helper returns 1 if a call to add_buf will not fail > with -ENOSPC. > > This will help callers that do > > while(1) { > alloc() > if (add_buf()) { > free(); > break; > } > } > > This will result in one less alloc/free exercise.Hi Amit, This is what I have in my tree; similar motivation. I didn't adapt virtio_net like you did tho. virtio: make add_buf return capacity remaining This API change means that virtio_net can tell how much capacity remains for buffers. It's necessarily fuzzy, since VIRTIO_RING_F_INDIRECT_DESC means we can fit any number of descriptors in one, *if* we can kmalloc. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> Cc: Dinesh Subhraveti <dineshs at us.ibm.com> --- drivers/block/virtio_blk.c | 2 +- drivers/char/hw_random/virtio-rng.c | 2 +- drivers/char/virtio_console.c | 4 ++-- drivers/net/virtio_net.c | 8 ++++---- drivers/virtio/virtio_balloon.c | 2 +- drivers/virtio/virtio_ring.c | 6 +++++- include/linux/virtio.h | 2 +- net/9p/trans_virtio.c | 2 +- 8 files changed, 16 insertions(+), 12 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -139,7 +139,7 @@ static bool do_req(struct request_queue } } - if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) { + if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr) < 0) { mempool_free(vbr, vblk->pool); return false; } diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -51,7 +51,7 @@ static void register_buffer(void) sg_init_one(&sg, random_data+data_left, RANDOM_DATA_SIZE-data_left); /* There should always be room for one buffer. */ - if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0) + if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) < 0) BUG(); vq->vq_ops->kick(vq); } diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -65,7 +65,7 @@ static int put_chars(u32 vtermno, const /* add_buf wants a token to identify this buffer: we hand it any * non-NULL pointer, since there's only ever one buffer. */ - if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) { + if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) { /* Tell Host to go! */ out_vq->vq_ops->kick(out_vq); /* Chill out until it's done with the buffer. */ @@ -85,7 +85,7 @@ static void add_inbuf(void) sg_init_one(sg, inbuf, PAGE_SIZE); /* We should always be able to add one buffer to an empty queue. */ - if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0) + if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) < 0) BUG(); in_vq->vq_ops->kick(in_vq); } diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -300,7 +300,7 @@ static void try_fill_recv_maxbufs(struct skb_queue_head(&vi->recv, skb); err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb); - if (err) { + if (err < 0) { skb_unlink(skb, &vi->recv); trim_pages(vi, skb); kfree_skb(skb); @@ -349,7 +349,7 @@ static void try_fill_recv(struct virtnet skb_queue_head(&vi->recv, skb); err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 1, skb); - if (err) { + if (err < 0) { skb_unlink(skb, &vi->recv); kfree_skb(skb); break; @@ -480,7 +480,7 @@ again: /* Put new one in send queue and do transmit */ __skb_queue_head(&vi->send, skb); - if (likely(xmit_skb(vi, skb) == 0)) { + if (likely(xmit_skb(vi, skb) >= 0)) { vi->svq->vq_ops->kick(vi->svq); /* Don't wait up for transmitted skbs to be freed. */ skb_orphan(skb); @@ -577,7 +577,7 @@ static bool virtnet_send_command(struct sg_set_buf(&sg[i + 1], sg_virt(s), s->length); sg_set_buf(&sg[out + in - 1], &status, sizeof(status)); - BUG_ON(vi->cvq->vq_ops->add_buf(vi->cvq, sg, out, in, vi)); + BUG_ON(vi->cvq->vq_ops->add_buf(vi->cvq, sg, out, in, vi) < 0); vi->cvq->vq_ops->kick(vi->cvq); diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -84,7 +84,7 @@ static void tell_host(struct virtio_ball init_completion(&vb->acked); /* We should always be able to add one buffer to an empty queue. */ - if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0) + if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0) BUG(); vq->vq_ops->kick(vq); diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -213,7 +213,11 @@ add_head: pr_debug("Added buffer head %i to %p\n", head, vq); END_USE(vq); - return 0; + + /* If we're indirect, we can fit many (assuming not OOM). */ + if (vq->indirect) + return vq->num_free ? vq->vring.num : 0; + return vq->num_free; } static void vring_kick(struct virtqueue *_vq) diff --git a/include/linux/virtio.h b/include/linux/virtio.h --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -34,7 +34,7 @@ struct virtqueue { * out_num: the number of sg readable by other side * in_num: the number of sg which are writable (after readable ones) * data: the token identifying the buffer. - * Returns 0 or an error. + * Returns remaining capacity of queue (sg segments) or a negative error. * @kick: update after add_buf * vq: the struct virtqueue * After one or more add_buf calls, invoke this to kick the other side. diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -203,7 +203,7 @@ p9_virtio_request(struct p9_client *clie req->status = REQ_STATUS_SENT; - if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc)) { + if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, req->tc) < 0) { P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc add_buf returned failure"); return -EIO;