From patchwork Fri Dec 18 07:44:49 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shirley Ma X-Patchwork-Id: 41378 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 4793D1007D2 for ; Fri, 18 Dec 2009 18:45:08 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751248AbZLRHo7 (ORCPT ); Fri, 18 Dec 2009 02:44:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751154AbZLRHo6 (ORCPT ); Fri, 18 Dec 2009 02:44:58 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:33380 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751116AbZLRHo5 (ORCPT ); Fri, 18 Dec 2009 02:44:57 -0500 Received: from d03relay05.boulder.ibm.com (d03relay05.boulder.ibm.com [9.17.195.107]) by e35.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id nBI7W9sA013662; Fri, 18 Dec 2009 00:32:09 -0700 Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d03relay05.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nBI7ip58126886; Fri, 18 Dec 2009 00:44:51 -0700 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nBI7ip0u030357; Fri, 18 Dec 2009 00:44:51 -0700 Received: from [9.49.136.215] (sig-9-49-136-215.mts.ibm.com [9.49.136.215]) by d03av03.boulder.ibm.com (8.14.3/8.13.1/NCO v10.0 AVin) with ESMTP id nBI7ioIk030348; Fri, 18 Dec 2009 00:44:51 -0700 Subject: [PATCH 2/2] virtio_net: Defer skb allocation in receive path From: Shirley Ma To: Rusty Russell Cc: "Michael S. Tsirkin" , Avi Kivity , netdev@vger.kernel.org, kvm@vger.kernel.org In-Reply-To: <1261122090.4148.24.camel@localhost.localdomain> References: <1261122090.4148.24.camel@localhost.localdomain> Date: Thu, 17 Dec 2009 23:44:49 -0800 Message-Id: <1261122289.4148.27.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 (2.24.5-2.fc10) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- drivers/net/virtio_net.c | 426 +++++++++++++++++++++++++++------------------- 1 files changed, 247 insertions(+), 179 deletions(-) -- 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..bb57b96 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; + 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 (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; - } +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 (vi->mergeable_rx_bufs) { - unsigned int copy; - char *p = page_address(skb_shinfo(skb)->frags[0].page); + p = page_address(page); - if (len > PAGE_SIZE) - len = PAGE_SIZE; - len -= sizeof(struct virtio_net_hdr_mrg_rxbuf); + /* 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; - memcpy(&hdr->mhdr, p, sizeof(hdr->mhdr)); - p += sizeof(hdr->mhdr); + hdr = skb_vnet_hdr(skb); - copy = len; - if (copy > skb_tailroom(skb)) - copy = skb_tailroom(skb); + 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); + } - memcpy(skb_put(skb, copy), p, copy); + memcpy(hdr, p, hdr_len); - len -= copy; + len -= hdr_len; + p += offset; - 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; - } + copy = len; + if (copy > skb_tailroom(skb)) + copy = skb_tailroom(skb); + memcpy(skb_put(skb, copy), p, copy); - while (--hdr->mhdr.num_buffers) { - struct sk_buff *nskb; + len -= copy; + offset += 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; - } - - 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; - if (len <= MAX_PACKET_LEN) - trim_pages(vi, skb); + set_skb_frag(skb, page, 0, &len); + + --vi->num; + } + return 0; +} - err = pskb_trim(skb, len); - if (err) { - pr_debug("%s: pskb_trim failed %i %d\n", dev->name, - len, err); +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 (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; + } + + 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 +1011,34 @@ free: return err; } +static void free_unused_bufs(struct virtnet_info *vi) +{ + void *buf; + while (vi->num) { + buf = vi->rvq->vq_ops->detach_unused_buf(vi->rvq); + if (!buf) + continue; + if (vi->mergeable_rx_bufs || vi->big_packets) + give_pages(vi, buf); + else + dev_kfree_skb(buf); + --vi->num; + } +} + 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);