[v2,2/2] virtio_net: Defer skb allocation in receive path

Message ID	1263416018.29594.1.camel@localhost.localdomain
State	RFC, archived
Delegated to:	David Miller
Headers	show Return-Path: <netdev-owner@vger.kernel.org> Subject: [PATCH v2 2/2] virtio_net: Defer skb allocation in receive path From: Shirley Ma <mashirle@us.ibm.com> To: "Michael S. Tsirkin" <mst@redhat.com> Cc: Amit Shah <amit.shah@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, Avi Kivity <avi@redhat.com>, netdev@vger.kernel.org, kvm@vger.kernel.org In-Reply-To: <1263236965.11949.1.camel@localhost.localdomain> References: <1261122090.4148.24.camel@localhost.localdomain> <1261122289.4148.27.camel@localhost.localdomain> <20091224133749.GB2855@amit-x200.redhat.com> <1262640344.18773.2.camel@localhost.localdomain> <20100104211454.GB21488@redhat.com> <1263236965.11949.1.camel@localhost.localdomain> Content-Type: text/plain; charset="UTF-8" Date: Wed, 13 Jan 2010 12:53:38 -0800 Message-ID: <1263416018.29594.1.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk

On Wed, Jan 13, 2010 at 12:53:38PM -0800, Shirley Ma wrote: > virtio_net receives packets from its pre-allocated vring buffers, then it > delivers these packets to upper layer protocols as skb buffs. So it's not > necessary to pre-allocate skb for each mergable buffer, then frees extra > skbs when buffers are merged into a large packet. This patch has deferred > skb allocation in receiving packets for both big packets and mergeable buffers > to reduce skb pre-allocations and skb frees. It frees unused buffers by calling > detach_unused_buf in vring, so recv skb queue is not needed. > > Signed-off-by: Shirley Ma <xma@us.ibm.com> > --- > drivers/net/virtio_net.c | 427 +++++++++++++++++++++++++++------------------- > 1 files changed, 248 insertions(+), 179 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index c708ecc..72b3f21 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -56,8 +56,7 @@ struct virtnet_info > /* Host will merge rx buffers for big packets (shake it! shake it!) */ > bool mergeable_rx_bufs; > > - /* Receive & send queues. */ > - struct sk_buff_head recv; > + /* Send queue. */ > struct sk_buff_head send; > How hard is it to get rid of send queue, btw? > /* Work struct for refilling if we run low on memory. */ > @@ -75,34 +74,44 @@ struct skb_vnet_hdr { > unsigned int num_sg; > }; > > +struct padded_vnet_hdr { > + struct virtio_net_hdr hdr; > + /* > + * virtio_net_hdr should be in a separated sg buffer because of a > + * QEMU bug, and data sg buffer shares same page with this header sg. > + * This padding makes next sg 16 byte aligned after virtio_net_hdr. > + */ > + char padding[6]; > +}; > + > static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb) > { > return (struct skb_vnet_hdr *)skb->cb; > } > > -static void give_a_page(struct virtnet_info *vi, struct page *page) > -{ > - page->private = (unsigned long)vi->pages; > - vi->pages = page; > -} > - > -static void trim_pages(struct virtnet_info *vi, struct sk_buff *skb) > +/* > + * private is used to chain pages for big packets, put the whole > + * most recent used list in the beginning for reuse > + */ > +static void give_pages(struct virtnet_info *vi, struct page *page) > { > - unsigned int i; > + struct page *end; > > - for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) > - give_a_page(vi, skb_shinfo(skb)->frags[i].page); > - skb_shinfo(skb)->nr_frags = 0; > - skb->data_len = 0; > + /* Find end of list, sew whole thing into vi->pages. */ > + for (end = page; end->private; end = (struct page *)end->private); > + end->private = (unsigned long)vi->pages; > + vi->pages = page; > } > > static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask) > { > struct page *p = vi->pages; > > - if (p) > + if (p) { > vi->pages = (struct page *)p->private; > - else > + /* clear private here, it is used to chain pages */ > + p->private = 0; > + } else > p = alloc_page(gfp_mask); > return p; > } > @@ -118,99 +127,142 @@ static void skb_xmit_done(struct virtqueue *svq) > netif_wake_queue(vi->dev); > } > > -static void receive_skb(struct net_device *dev, struct sk_buff *skb, > - unsigned len) > +static void set_skb_frag(struct sk_buff *skb, struct page *page, > + unsigned int offset, unsigned int *len) > { > - struct virtnet_info *vi = netdev_priv(dev); > - struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb); > - int err; > - int i; > - > - if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) { > - pr_debug("%s: short packet %i\n", dev->name, len); > - dev->stats.rx_length_errors++; > - goto drop; > - } > + int i = skb_shinfo(skb)->nr_frags; > + skb_frag_t *f; > + > + f = &skb_shinfo(skb)->frags[i]; > + f->size = min((unsigned)PAGE_SIZE - offset, *len); > + f->page_offset = offset; > + f->page = page; > + > + skb->data_len += f->size; > + skb->len += f->size; > + skb_shinfo(skb)->nr_frags++; > + *len -= f->size; > +} > > - if (vi->mergeable_rx_bufs) { > - unsigned int copy; > - char *p = page_address(skb_shinfo(skb)->frags[0].page); > +static struct sk_buff *page_to_skb(struct virtnet_info *vi, > + struct page *page, unsigned int len) > +{ > + struct sk_buff *skb; > + struct skb_vnet_hdr *hdr; > + unsigned int copy, hdr_len, offset; > + char *p; > > - if (len > PAGE_SIZE) > - len = PAGE_SIZE; > - len -= sizeof(struct virtio_net_hdr_mrg_rxbuf); > + p = page_address(page); > > - memcpy(&hdr->mhdr, p, sizeof(hdr->mhdr)); > - p += sizeof(hdr->mhdr); > + /* copy small packet so we can reuse these pages for small data */ > + skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); > + if (unlikely(!skb)) > + return NULL; > > - copy = len; > - if (copy > skb_tailroom(skb)) > - copy = skb_tailroom(skb); > + hdr = skb_vnet_hdr(skb); > > - memcpy(skb_put(skb, copy), p, copy); > + if (vi->mergeable_rx_bufs) { > + hdr_len = sizeof hdr->mhdr; > + offset = hdr_len; > + } else { > + hdr_len = sizeof hdr->hdr; > + offset = sizeof(struct padded_vnet_hdr); > + } > > - len -= copy; > + memcpy(hdr, p, hdr_len); > > - if (!len) { > - give_a_page(vi, skb_shinfo(skb)->frags[0].page); > - skb_shinfo(skb)->nr_frags--; > - } else { > - skb_shinfo(skb)->frags[0].page_offset += > - sizeof(hdr->mhdr) + copy; > - skb_shinfo(skb)->frags[0].size = len; > - skb->data_len += len; > - skb->len += len; > - } > + len -= hdr_len; > + p += offset; > > - while (--hdr->mhdr.num_buffers) { > - struct sk_buff *nskb; > + copy = len; > + if (copy > skb_tailroom(skb)) > + copy = skb_tailroom(skb); > + memcpy(skb_put(skb, copy), p, copy); > > - i = skb_shinfo(skb)->nr_frags; > - if (i >= MAX_SKB_FRAGS) { > - pr_debug("%s: packet too long %d\n", dev->name, > - len); > - dev->stats.rx_length_errors++; > - goto drop; > - } > + len -= copy; > + offset += copy; > > - nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len); > - if (!nskb) { > - pr_debug("%s: rx error: %d buffers missing\n", > - dev->name, hdr->mhdr.num_buffers); > - dev->stats.rx_length_errors++; > - goto drop; > - } > + while (len) { > + set_skb_frag(skb, page, offset, &len); > + page = (struct page *)page->private; > + offset = 0; > + } > > - __skb_unlink(nskb, &vi->recv); > - vi->num--; > + if (page) > + give_pages(vi, page); > > - skb_shinfo(skb)->frags[i] = skb_shinfo(nskb)->frags[0]; > - skb_shinfo(nskb)->nr_frags = 0; > - kfree_skb(nskb); > + return skb; > +} > > - if (len > PAGE_SIZE) > - len = PAGE_SIZE; > +static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb) > +{ > + struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb); > + struct page *page; > + int num_buf, i, len; > + > + num_buf = hdr->mhdr.num_buffers; > + while (--num_buf) { > + i = skb_shinfo(skb)->nr_frags; > + if (i >= MAX_SKB_FRAGS) { > + pr_debug("%s: packet too long\n", skb->dev->name); > + skb->dev->stats.rx_length_errors++; > + return -EINVAL; > + } > > - skb_shinfo(skb)->frags[i].size = len; > - skb_shinfo(skb)->nr_frags++; > - skb->data_len += len; > - skb->len += len; > + page = vi->rvq->vq_ops->get_buf(vi->rvq, &len); > + if (!page) { > + pr_debug("%s: rx error: %d buffers missing\n", > + skb->dev->name, hdr->mhdr.num_buffers); > + skb->dev->stats.rx_length_errors++; > + return -EINVAL; > } > - } else { > - len -= sizeof(hdr->hdr); > + if (len > PAGE_SIZE) > + len = PAGE_SIZE; > + > + set_skb_frag(skb, page, 0, &len); > + > + --vi->num; > + } > + return 0; > +} > + > +static void receive_buf(struct net_device *dev, void *buf, unsigned int len) > +{ > + struct virtnet_info *vi = netdev_priv(dev); > + struct sk_buff *skb; > + struct page *page; > + struct skb_vnet_hdr *hdr; > > - if (len <= MAX_PACKET_LEN) > - trim_pages(vi, skb); > + if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) { > + pr_debug("%s: short packet %i\n", dev->name, len); > + dev->stats.rx_length_errors++; > + if (vi->mergeable_rx_bufs || vi->big_packets) > + give_pages(vi, buf); > + else > + dev_kfree_skb(buf); > + return; > + } > > - err = pskb_trim(skb, len); > - if (err) { > - pr_debug("%s: pskb_trim failed %i %d\n", dev->name, > - len, err); > + if (!vi->mergeable_rx_bufs && !vi->big_packets) { > + skb = buf; > + len -= sizeof(struct virtio_net_hdr); > + skb_trim(skb, len); > + } else { > + page = buf; > + skb = page_to_skb(vi, page, len); > + if (unlikely(!skb)) { > dev->stats.rx_dropped++; > - goto drop; > + give_pages(vi, page); > + return; > } > + if (vi->mergeable_rx_bufs) > + if (receive_mergeable(vi, skb)) { > + dev_kfree_skb(skb); > + return; > + } > } > > + hdr = skb_vnet_hdr(skb); > skb->truesize += skb->data_len; > dev->stats.rx_bytes += skb->len; > dev->stats.rx_packets++; > @@ -267,110 +319,119 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb, > > frame_err: > dev->stats.rx_frame_errors++; > -drop: > dev_kfree_skb(skb); > } > > -static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp) > +static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp) > { > struct sk_buff *skb; > - struct scatterlist sg[2+MAX_SKB_FRAGS]; > - int num, err, i; > - bool oom = false; > - > - sg_init_table(sg, 2+MAX_SKB_FRAGS); > - do { > - struct skb_vnet_hdr *hdr; > + struct skb_vnet_hdr *hdr; > + struct scatterlist sg[2]; > + int err; > > - skb = netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN); > - if (unlikely(!skb)) { > - oom = true; > - break; > - } > + skb = netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN); > + if (unlikely(!skb)) > + return -ENOMEM; > > - skb_put(skb, MAX_PACKET_LEN); > + skb_put(skb, MAX_PACKET_LEN); > > - hdr = skb_vnet_hdr(skb); > - sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr)); > + hdr = skb_vnet_hdr(skb); > + sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr); > > - if (vi->big_packets) { > - for (i = 0; i < MAX_SKB_FRAGS; i++) { > - skb_frag_t *f = &skb_shinfo(skb)->frags[i]; > - f->page = get_a_page(vi, gfp); > - if (!f->page) > - break; > + skb_to_sgvec(skb, sg + 1, 0, skb->len); > > - f->page_offset = 0; > - f->size = PAGE_SIZE; > + err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 2, skb); > + if (err < 0) > + dev_kfree_skb(skb); > > - skb->data_len += PAGE_SIZE; > - skb->len += PAGE_SIZE; > + return err; > +} > > - skb_shinfo(skb)->nr_frags++; > - } > +static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp) > +{ > + struct scatterlist sg[MAX_SKB_FRAGS + 2]; > + struct page *first, *list = NULL; > + char *p; > + int i, err, offset; > + > + /* page in sg[MAX_SKB_FRAGS + 1] is list tail */ > + for (i = MAX_SKB_FRAGS + 1; i > 1; --i) { > + first = get_a_page(vi, gfp); > + if (!first) { > + if (list) > + give_pages(vi, list); > + return -ENOMEM; > } > + sg_set_buf(&sg[i], page_address(first), PAGE_SIZE); > > - num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; > - skb_queue_head(&vi->recv, skb); > + /* chain new page in list head to match sg */ > + first->private = (unsigned long)list; > + list = first; > + } > > - err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb); > - if (err < 0) { > - skb_unlink(skb, &vi->recv); > - trim_pages(vi, skb); > - kfree_skb(skb); > - break; > - } > - vi->num++; > - } while (err >= num); > - if (unlikely(vi->num > vi->max)) > - vi->max = vi->num; > - vi->rvq->vq_ops->kick(vi->rvq); > - return !oom; > + first = get_a_page(vi, gfp); > + if (!first) { > + give_pages(vi, list); > + return -ENOMEM; > + } > + p = page_address(first); > + > + /* sg[0], sg[1] share the same page */ > + /* a separated sg[0] for virtio_net_hdr only during to QEMU bug*/ > + sg_set_buf(&sg[0], p, sizeof(struct virtio_net_hdr)); > + > + /* sg[1] for data packet, from offset */ > + offset = sizeof(struct padded_vnet_hdr); > + sg_set_buf(&sg[1], p + offset, PAGE_SIZE - offset); > + > + /* chain first in list head */ > + first->private = (unsigned long)list; > + err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, MAX_SKB_FRAGS + 2, > + first); > + if (err < 0) > + give_pages(vi, first); > + > + return err; > } > > -/* Returns false if we couldn't fill entirely (OOM). */ > -static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp) > +static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp) > { > - struct sk_buff *skb; > - struct scatterlist sg[1]; > + struct page *page; > + struct scatterlist sg; > int err; > - bool oom = false; > - > - if (!vi->mergeable_rx_bufs) > - return try_fill_recv_maxbufs(vi, gfp); > > - do { > - skb_frag_t *f; > + page = get_a_page(vi, gfp); > + if (!page) > + return -ENOMEM; > > - skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); > - if (unlikely(!skb)) { > - oom = true; > - break; > - } > + sg_init_one(&sg, page_address(page), PAGE_SIZE); > > - f = &skb_shinfo(skb)->frags[0]; > - f->page = get_a_page(vi, gfp); > - if (!f->page) { > - oom = true; > - kfree_skb(skb); > - break; > - } > + err = vi->rvq->vq_ops->add_buf(vi->rvq, &sg, 0, 1, page); > + if (err < 0) > + give_pages(vi, page); > > - f->page_offset = 0; > - f->size = PAGE_SIZE; > + return err; > +} > > - skb_shinfo(skb)->nr_frags++; > +/* Returns false if we couldn't fill entirely (OOM). */ > +static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp) > +{ > + int err; > + bool oom = false; > > - sg_init_one(sg, page_address(f->page), PAGE_SIZE); > - skb_queue_head(&vi->recv, skb); > + do { > + if (vi->mergeable_rx_bufs) > + err = add_recvbuf_mergeable(vi, gfp); > + else if (vi->big_packets) > + err = add_recvbuf_big(vi, gfp); > + else > + err = add_recvbuf_small(vi, gfp); > > - err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 1, skb); > if (err < 0) { > - skb_unlink(skb, &vi->recv); > - kfree_skb(skb); > + oom = true; > break; > } > - vi->num++; > + ++vi->num; > } while (err > 0); > if (unlikely(vi->num > vi->max)) > vi->max = vi->num; > @@ -408,15 +469,14 @@ static void refill_work(struct work_struct *work) > static int virtnet_poll(struct napi_struct *napi, int budget) > { > struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi); > - struct sk_buff *skb = NULL; > + void *buf; > unsigned int len, received = 0; > > again: > while (received < budget && > - (skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) { > - __skb_unlink(skb, &vi->recv); > - receive_skb(vi->dev, skb, len); > - vi->num--; > + (buf = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) { > + receive_buf(vi->dev, buf, len); > + --vi->num; > received++; > } > > @@ -496,9 +556,9 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) > > /* Encode metadata header at front. */ > if (vi->mergeable_rx_bufs) > - sg_set_buf(sg, &hdr->mhdr, sizeof(hdr->mhdr)); > + sg_set_buf(sg, &hdr->mhdr, sizeof hdr->mhdr); > else > - sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr)); > + sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr); > > hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; > return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb); > @@ -916,8 +976,7 @@ static int virtnet_probe(struct virtio_device *vdev) > dev->features |= NETIF_F_HW_VLAN_FILTER; > } > > - /* Initialize our empty receive and send queues. */ > - skb_queue_head_init(&vi->recv); > + /* Initialize our empty send queue. */ > skb_queue_head_init(&vi->send); > > err = register_netdev(dev); > @@ -952,25 +1011,35 @@ free: > return err; > } > > +static void free_unused_bufs(struct virtnet_info *vi) > +{ > + void *buf; > + while (1) { > + buf = vi->rvq->vq_ops->detach_unused_buf(vi->rvq); > + if (!buf) > + break; > + if (vi->mergeable_rx_bufs || vi->big_packets) > + give_pages(vi, buf); > + else > + dev_kfree_skb(buf); > + --vi->num; > + } > + BUG_ON(vi->num != 0); > +} > + > static void __devexit virtnet_remove(struct virtio_device *vdev) > { > struct virtnet_info *vi = vdev->priv; > - struct sk_buff *skb; > > /* Stop all the virtqueues. */ > vdev->config->reset(vdev); > > - /* Free our skbs in send and recv queues, if any. */ > - while ((skb = __skb_dequeue(&vi->recv)) != NULL) { > - kfree_skb(skb); > - vi->num--; > - } > + /* Free our skbs in send queue, if any. */ > __skb_queue_purge(&vi->send); > > - BUG_ON(vi->num != 0); > - > unregister_netdev(vi->dev); > cancel_delayed_work_sync(&vi->refill); > + free_unused_bufs(vi); > > vdev->config->del_vqs(vi->vdev); > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index c708ecc..72b3f21 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -56,8 +56,7 @@ struct virtnet_info /* Host will merge rx buffers for big packets (shake it! shake it!) */ bool mergeable_rx_bufs; - /* Receive & send queues. */ - struct sk_buff_head recv; + /* Send queue. */ struct sk_buff_head send; /* Work struct for refilling if we run low on memory. */ @@ -75,34 +74,44 @@ struct skb_vnet_hdr { unsigned int num_sg; }; +struct padded_vnet_hdr { + struct virtio_net_hdr hdr; + /* + * virtio_net_hdr should be in a separated sg buffer because of a + * QEMU bug, and data sg buffer shares same page with this header sg. + * This padding makes next sg 16 byte aligned after virtio_net_hdr. + */ + char padding[6]; +}; + static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb) { return (struct skb_vnet_hdr *)skb->cb; } -static void give_a_page(struct virtnet_info *vi, struct page *page) -{ - page->private = (unsigned long)vi->pages; - vi->pages = page; -} - -static void trim_pages(struct virtnet_info *vi, struct sk_buff *skb) +/* + * private is used to chain pages for big packets, put the whole + * most recent used list in the beginning for reuse + */ +static void give_pages(struct virtnet_info *vi, struct page *page) { - unsigned int i; + struct page *end; - for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) - give_a_page(vi, skb_shinfo(skb)->frags[i].page); - skb_shinfo(skb)->nr_frags = 0; - skb->data_len = 0; + /* Find end of list, sew whole thing into vi->pages. */ + for (end = page; end->private; end = (struct page *)end->private); + end->private = (unsigned long)vi->pages; + vi->pages = page; } static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask) { struct page *p = vi->pages; - if (p) + if (p) { vi->pages = (struct page *)p->private; - else + /* clear private here, it is used to chain pages */ + p->private = 0; + } else p = alloc_page(gfp_mask); return p; } @@ -118,99 +127,142 @@ static void skb_xmit_done(struct virtqueue *svq) netif_wake_queue(vi->dev); } -static void receive_skb(struct net_device *dev, struct sk_buff *skb, - unsigned len) +static void set_skb_frag(struct sk_buff *skb, struct page *page, + unsigned int offset, unsigned int *len) { - struct virtnet_info *vi = netdev_priv(dev); - struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb); - int err; - int i; - - if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) { - pr_debug("%s: short packet %i\n", dev->name, len); - dev->stats.rx_length_errors++; - goto drop; - } + int i = skb_shinfo(skb)->nr_frags; + skb_frag_t *f; + + f = &skb_shinfo(skb)->frags[i]; + f->size = min((unsigned)PAGE_SIZE - offset, *len); + f->page_offset = offset; + f->page = page; + + skb->data_len += f->size; + skb->len += f->size; + skb_shinfo(skb)->nr_frags++; + *len -= f->size; +} - if (vi->mergeable_rx_bufs) { - unsigned int copy; - char *p = page_address(skb_shinfo(skb)->frags[0].page); +static struct sk_buff *page_to_skb(struct virtnet_info *vi, + struct page *page, unsigned int len) +{ + struct sk_buff *skb; + struct skb_vnet_hdr *hdr; + unsigned int copy, hdr_len, offset; + char *p; - if (len > PAGE_SIZE) - len = PAGE_SIZE; - len -= sizeof(struct virtio_net_hdr_mrg_rxbuf); + p = page_address(page); - memcpy(&hdr->mhdr, p, sizeof(hdr->mhdr)); - p += sizeof(hdr->mhdr); + /* copy small packet so we can reuse these pages for small data */ + skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); + if (unlikely(!skb)) + return NULL; - copy = len; - if (copy > skb_tailroom(skb)) - copy = skb_tailroom(skb); + hdr = skb_vnet_hdr(skb); - memcpy(skb_put(skb, copy), p, copy); + if (vi->mergeable_rx_bufs) { + hdr_len = sizeof hdr->mhdr; + offset = hdr_len; + } else { + hdr_len = sizeof hdr->hdr; + offset = sizeof(struct padded_vnet_hdr); + } - len -= copy; + memcpy(hdr, p, hdr_len); - if (!len) { - give_a_page(vi, skb_shinfo(skb)->frags[0].page); - skb_shinfo(skb)->nr_frags--; - } else { - skb_shinfo(skb)->frags[0].page_offset += - sizeof(hdr->mhdr) + copy; - skb_shinfo(skb)->frags[0].size = len; - skb->data_len += len; - skb->len += len; - } + len -= hdr_len; + p += offset; - while (--hdr->mhdr.num_buffers) { - struct sk_buff *nskb; + copy = len; + if (copy > skb_tailroom(skb)) + copy = skb_tailroom(skb); + memcpy(skb_put(skb, copy), p, copy); - i = skb_shinfo(skb)->nr_frags; - if (i >= MAX_SKB_FRAGS) { - pr_debug("%s: packet too long %d\n", dev->name, - len); - dev->stats.rx_length_errors++; - goto drop; - } + len -= copy; + offset += copy; - nskb = vi->rvq->vq_ops->get_buf(vi->rvq, &len); - if (!nskb) { - pr_debug("%s: rx error: %d buffers missing\n", - dev->name, hdr->mhdr.num_buffers); - dev->stats.rx_length_errors++; - goto drop; - } + while (len) { + set_skb_frag(skb, page, offset, &len); + page = (struct page *)page->private; + offset = 0; + } - __skb_unlink(nskb, &vi->recv); - vi->num--; + if (page) + give_pages(vi, page); - skb_shinfo(skb)->frags[i] = skb_shinfo(nskb)->frags[0]; - skb_shinfo(nskb)->nr_frags = 0; - kfree_skb(nskb); + return skb; +} - if (len > PAGE_SIZE) - len = PAGE_SIZE; +static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb) +{ + struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb); + struct page *page; + int num_buf, i, len; + + num_buf = hdr->mhdr.num_buffers; + while (--num_buf) { + i = skb_shinfo(skb)->nr_frags; + if (i >= MAX_SKB_FRAGS) { + pr_debug("%s: packet too long\n", skb->dev->name); + skb->dev->stats.rx_length_errors++; + return -EINVAL; + } - skb_shinfo(skb)->frags[i].size = len; - skb_shinfo(skb)->nr_frags++; - skb->data_len += len; - skb->len += len; + page = vi->rvq->vq_ops->get_buf(vi->rvq, &len); + if (!page) { + pr_debug("%s: rx error: %d buffers missing\n", + skb->dev->name, hdr->mhdr.num_buffers); + skb->dev->stats.rx_length_errors++; + return -EINVAL; } - } else { - len -= sizeof(hdr->hdr); + if (len > PAGE_SIZE) + len = PAGE_SIZE; + + set_skb_frag(skb, page, 0, &len); + + --vi->num; + } + return 0; +} + +static void receive_buf(struct net_device *dev, void *buf, unsigned int len) +{ + struct virtnet_info *vi = netdev_priv(dev); + struct sk_buff *skb; + struct page *page; + struct skb_vnet_hdr *hdr; - if (len <= MAX_PACKET_LEN) - trim_pages(vi, skb); + if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) { + pr_debug("%s: short packet %i\n", dev->name, len); + dev->stats.rx_length_errors++; + if (vi->mergeable_rx_bufs || vi->big_packets) + give_pages(vi, buf); + else + dev_kfree_skb(buf); + return; + } - err = pskb_trim(skb, len); - if (err) { - pr_debug("%s: pskb_trim failed %i %d\n", dev->name, - len, err); + if (!vi->mergeable_rx_bufs && !vi->big_packets) { + skb = buf; + len -= sizeof(struct virtio_net_hdr); + skb_trim(skb, len); + } else { + page = buf; + skb = page_to_skb(vi, page, len); + if (unlikely(!skb)) { dev->stats.rx_dropped++; - goto drop; + give_pages(vi, page); + return; } + if (vi->mergeable_rx_bufs) + if (receive_mergeable(vi, skb)) { + dev_kfree_skb(skb); + return; + } } + hdr = skb_vnet_hdr(skb); skb->truesize += skb->data_len; dev->stats.rx_bytes += skb->len; dev->stats.rx_packets++; @@ -267,110 +319,119 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb, frame_err: dev->stats.rx_frame_errors++; -drop: dev_kfree_skb(skb); } -static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp) +static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp) { struct sk_buff *skb; - struct scatterlist sg[2+MAX_SKB_FRAGS]; - int num, err, i; - bool oom = false; - - sg_init_table(sg, 2+MAX_SKB_FRAGS); - do { - struct skb_vnet_hdr *hdr; + struct skb_vnet_hdr *hdr; + struct scatterlist sg[2]; + int err; - skb = netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN); - if (unlikely(!skb)) { - oom = true; - break; - } + skb = netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN); + if (unlikely(!skb)) + return -ENOMEM; - skb_put(skb, MAX_PACKET_LEN); + skb_put(skb, MAX_PACKET_LEN); - hdr = skb_vnet_hdr(skb); - sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr)); + hdr = skb_vnet_hdr(skb); + sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr); - if (vi->big_packets) { - for (i = 0; i < MAX_SKB_FRAGS; i++) { - skb_frag_t *f = &skb_shinfo(skb)->frags[i]; - f->page = get_a_page(vi, gfp); - if (!f->page) - break; + skb_to_sgvec(skb, sg + 1, 0, skb->len); - f->page_offset = 0; - f->size = PAGE_SIZE; + err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 2, skb); + if (err < 0) + dev_kfree_skb(skb); - skb->data_len += PAGE_SIZE; - skb->len += PAGE_SIZE; + return err; +} - skb_shinfo(skb)->nr_frags++; - } +static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp) +{ + struct scatterlist sg[MAX_SKB_FRAGS + 2]; + struct page *first, *list = NULL; + char *p; + int i, err, offset; + + /* page in sg[MAX_SKB_FRAGS + 1] is list tail */ + for (i = MAX_SKB_FRAGS + 1; i > 1; --i) { + first = get_a_page(vi, gfp); + if (!first) { + if (list) + give_pages(vi, list); + return -ENOMEM; } + sg_set_buf(&sg[i], page_address(first), PAGE_SIZE); - num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; - skb_queue_head(&vi->recv, skb); + /* chain new page in list head to match sg */ + first->private = (unsigned long)list; + list = first; + } - err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb); - if (err < 0) { - skb_unlink(skb, &vi->recv); - trim_pages(vi, skb); - kfree_skb(skb); - break; - } - vi->num++; - } while (err >= num); - if (unlikely(vi->num > vi->max)) - vi->max = vi->num; - vi->rvq->vq_ops->kick(vi->rvq); - return !oom; + first = get_a_page(vi, gfp); + if (!first) { + give_pages(vi, list); + return -ENOMEM; + } + p = page_address(first); + + /* sg[0], sg[1] share the same page */ + /* a separated sg[0] for virtio_net_hdr only during to QEMU bug*/ + sg_set_buf(&sg[0], p, sizeof(struct virtio_net_hdr)); + + /* sg[1] for data packet, from offset */ + offset = sizeof(struct padded_vnet_hdr); + sg_set_buf(&sg[1], p + offset, PAGE_SIZE - offset); + + /* chain first in list head */ + first->private = (unsigned long)list; + err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, MAX_SKB_FRAGS + 2, + first); + if (err < 0) + give_pages(vi, first); + + return err; } -/* Returns false if we couldn't fill entirely (OOM). */ -static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp) +static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp) { - struct sk_buff *skb; - struct scatterlist sg[1]; + struct page *page; + struct scatterlist sg; int err; - bool oom = false; - - if (!vi->mergeable_rx_bufs) - return try_fill_recv_maxbufs(vi, gfp); - do { - skb_frag_t *f; + page = get_a_page(vi, gfp); + if (!page) + return -ENOMEM; - skb = netdev_alloc_skb_ip_align(vi->dev, GOOD_COPY_LEN); - if (unlikely(!skb)) { - oom = true; - break; - } + sg_init_one(&sg, page_address(page), PAGE_SIZE); - f = &skb_shinfo(skb)->frags[0]; - f->page = get_a_page(vi, gfp); - if (!f->page) { - oom = true; - kfree_skb(skb); - break; - } + err = vi->rvq->vq_ops->add_buf(vi->rvq, &sg, 0, 1, page); + if (err < 0) + give_pages(vi, page); - f->page_offset = 0; - f->size = PAGE_SIZE; + return err; +} - skb_shinfo(skb)->nr_frags++; +/* Returns false if we couldn't fill entirely (OOM). */ +static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp) +{ + int err; + bool oom = false; - sg_init_one(sg, page_address(f->page), PAGE_SIZE); - skb_queue_head(&vi->recv, skb); + do { + if (vi->mergeable_rx_bufs) + err = add_recvbuf_mergeable(vi, gfp); + else if (vi->big_packets) + err = add_recvbuf_big(vi, gfp); + else + err = add_recvbuf_small(vi, gfp); - err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 1, skb); if (err < 0) { - skb_unlink(skb, &vi->recv); - kfree_skb(skb); + oom = true; break; } - vi->num++; + ++vi->num; } while (err > 0); if (unlikely(vi->num > vi->max)) vi->max = vi->num; @@ -408,15 +469,14 @@ static void refill_work(struct work_struct *work) static int virtnet_poll(struct napi_struct *napi, int budget) { struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi); - struct sk_buff *skb = NULL; + void *buf; unsigned int len, received = 0; again: while (received < budget && - (skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) { - __skb_unlink(skb, &vi->recv); - receive_skb(vi->dev, skb, len); - vi->num--; + (buf = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) { + receive_buf(vi->dev, buf, len); + --vi->num; received++; } @@ -496,9 +556,9 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) /* Encode metadata header at front. */ if (vi->mergeable_rx_bufs) - sg_set_buf(sg, &hdr->mhdr, sizeof(hdr->mhdr)); + sg_set_buf(sg, &hdr->mhdr, sizeof hdr->mhdr); else - sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr)); + sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr); hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb); @@ -916,8 +976,7 @@ static int virtnet_probe(struct virtio_device *vdev) dev->features |= NETIF_F_HW_VLAN_FILTER; } - /* Initialize our empty receive and send queues. */ - skb_queue_head_init(&vi->recv); + /* Initialize our empty send queue. */ skb_queue_head_init(&vi->send); err = register_netdev(dev); @@ -952,25 +1011,35 @@ free: return err; } +static void free_unused_bufs(struct virtnet_info *vi) +{ + void *buf; + while (1) { + buf = vi->rvq->vq_ops->detach_unused_buf(vi->rvq); + if (!buf) + break; + if (vi->mergeable_rx_bufs || vi->big_packets) + give_pages(vi, buf); + else + dev_kfree_skb(buf); + --vi->num; + } + BUG_ON(vi->num != 0); +} + static void __devexit virtnet_remove(struct virtio_device *vdev) { struct virtnet_info *vi = vdev->priv; - struct sk_buff *skb; /* Stop all the virtqueues. */ vdev->config->reset(vdev); - /* Free our skbs in send and recv queues, if any. */ - while ((skb = __skb_dequeue(&vi->recv)) != NULL) { - kfree_skb(skb); - vi->num--; - } + /* Free our skbs in send queue, if any. */ __skb_queue_purge(&vi->send); - BUG_ON(vi->num != 0); - unregister_netdev(vi->dev); cancel_delayed_work_sync(&vi->refill); + free_unused_bufs(vi); vdev->config->del_vqs(vi->vdev);

[v2,2/2] virtio_net: Defer skb allocation in receive path

Commit Message

Comments

Patch