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Message-ID: <20230528021708-mutt-send-email-mst@kernel.org> Date: Sun, 28 May 2023 02:20:25 -0400 From: "Michael S. Tsirkin" <mst@...hat.com> To: Liang Chen <liangchen.linux@...il.com> Cc: jasowang@...hat.com, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, xuanzhuo@...ux.alibaba.com, kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net, pabeni@...hat.com, alexander.duyck@...il.com Subject: Re: [PATCH net-next 2/5] virtio_net: Add page_pool support to improve performance On Fri, May 26, 2023 at 01:46:18PM +0800, Liang Chen wrote: > The implementation at the moment uses one page per packet in both the > normal and XDP path. In addition, introducing a module parameter to enable > or disable the usage of page pool (disabled by default). > > In single-core vm testing environments, it gives a modest performance gain > in the normal path. > Upstream codebase: 47.5 Gbits/sec > Upstream codebase + page_pool support: 50.2 Gbits/sec > > In multi-core vm testing environments, The most significant performance > gain is observed in XDP cpumap: > Upstream codebase: 1.38 Gbits/sec > Upstream codebase + page_pool support: 9.74 Gbits/sec > > With this foundation, we can further integrate page pool fragmentation and > DMA map/unmap support. > > Signed-off-by: Liang Chen <liangchen.linux@...il.com> Why off by default? I am guessing it sometimes has performance costs too? What happens if we use page pool for big mode too? The less modes we have the better... > --- > drivers/net/virtio_net.c | 188 ++++++++++++++++++++++++++++++--------- > 1 file changed, 146 insertions(+), 42 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index c5dca0d92e64..99c0ca0c1781 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -31,6 +31,9 @@ module_param(csum, bool, 0444); > module_param(gso, bool, 0444); > module_param(napi_tx, bool, 0644); > > +static bool page_pool_enabled; > +module_param(page_pool_enabled, bool, 0400); > + > /* FIXME: MTU in config. */ > #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN) > #define GOOD_COPY_LEN 128 > @@ -159,6 +162,9 @@ struct receive_queue { > /* Chain pages by the private ptr. */ > struct page *pages; > > + /* Page pool */ > + struct page_pool *page_pool; > + > /* Average packet length for mergeable receive buffers. */ > struct ewma_pkt_len mrg_avg_pkt_len; > > @@ -459,6 +465,14 @@ static struct sk_buff *virtnet_build_skb(void *buf, unsigned int buflen, > return skb; > } > > +static void virtnet_put_page(struct receive_queue *rq, struct page *page) > +{ > + if (rq->page_pool) > + page_pool_put_full_page(rq->page_pool, page, true); > + else > + put_page(page); > +} > + > /* Called from bottom half context */ > static struct sk_buff *page_to_skb(struct virtnet_info *vi, > struct receive_queue *rq, > @@ -555,7 +569,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > hdr = skb_vnet_hdr(skb); > memcpy(hdr, hdr_p, hdr_len); > if (page_to_free) > - put_page(page_to_free); > + virtnet_put_page(rq, page_to_free); > > return skb; > } > @@ -802,7 +816,7 @@ static int virtnet_xdp_xmit(struct net_device *dev, > return ret; > } > > -static void put_xdp_frags(struct xdp_buff *xdp) > +static void put_xdp_frags(struct xdp_buff *xdp, struct receive_queue *rq) > { > struct skb_shared_info *shinfo; > struct page *xdp_page; > @@ -812,7 +826,7 @@ static void put_xdp_frags(struct xdp_buff *xdp) > shinfo = xdp_get_shared_info_from_buff(xdp); > for (i = 0; i < shinfo->nr_frags; i++) { > xdp_page = skb_frag_page(&shinfo->frags[i]); > - put_page(xdp_page); > + virtnet_put_page(rq, xdp_page); > } > } > } > @@ -903,7 +917,11 @@ static struct page *xdp_linearize_page(struct receive_queue *rq, > if (page_off + *len + tailroom > PAGE_SIZE) > return NULL; > > - page = alloc_page(GFP_ATOMIC); > + if (rq->page_pool) > + page = page_pool_dev_alloc_pages(rq->page_pool); > + else > + page = alloc_page(GFP_ATOMIC); > + > if (!page) > return NULL; > > @@ -926,21 +944,24 @@ static struct page *xdp_linearize_page(struct receive_queue *rq, > * is sending packet larger than the MTU. > */ > if ((page_off + buflen + tailroom) > PAGE_SIZE) { > - put_page(p); > + virtnet_put_page(rq, p); > goto err_buf; > } > > memcpy(page_address(page) + page_off, > page_address(p) + off, buflen); > page_off += buflen; > - put_page(p); > + virtnet_put_page(rq, p); > } > > /* Headroom does not contribute to packet length */ > *len = page_off - VIRTIO_XDP_HEADROOM; > return page; > err_buf: > - __free_pages(page, 0); > + if (rq->page_pool) > + page_pool_put_full_page(rq->page_pool, page, true); > + else > + __free_pages(page, 0); > return NULL; > } > > @@ -1144,7 +1165,7 @@ static void mergeable_buf_free(struct receive_queue *rq, int num_buf, > } > stats->bytes += len; > page = virt_to_head_page(buf); > - put_page(page); > + virtnet_put_page(rq, page); > } > } > > @@ -1264,7 +1285,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev, > cur_frag_size = truesize; > xdp_frags_truesz += cur_frag_size; > if (unlikely(len > truesize - room || cur_frag_size > PAGE_SIZE)) { > - put_page(page); > + virtnet_put_page(rq, page); > pr_debug("%s: rx error: len %u exceeds truesize %lu\n", > dev->name, len, (unsigned long)(truesize - room)); > dev->stats.rx_length_errors++; > @@ -1283,7 +1304,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev, > return 0; > > err: > - put_xdp_frags(xdp); > + put_xdp_frags(xdp, rq); > return -EINVAL; > } > > @@ -1344,7 +1365,10 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi, > if (*len + xdp_room > PAGE_SIZE) > return NULL; > > - xdp_page = alloc_page(GFP_ATOMIC); > + if (rq->page_pool) > + xdp_page = page_pool_dev_alloc_pages(rq->page_pool); > + else > + xdp_page = alloc_page(GFP_ATOMIC); > if (!xdp_page) > return NULL; > > @@ -1354,7 +1378,7 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi, > > *frame_sz = PAGE_SIZE; > > - put_page(*page); > + virtnet_put_page(rq, *page); > > *page = xdp_page; > > @@ -1400,6 +1424,8 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev, > head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz); > if (unlikely(!head_skb)) > break; > + if (rq->page_pool) > + skb_mark_for_recycle(head_skb); > return head_skb; > > case XDP_TX: > @@ -1410,10 +1436,10 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev, > break; > } > > - put_xdp_frags(&xdp); > + put_xdp_frags(&xdp, rq); > > err_xdp: > - put_page(page); > + virtnet_put_page(rq, page); > mergeable_buf_free(rq, num_buf, dev, stats); > > stats->xdp_drops++; > @@ -1467,6 +1493,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > head_skb = page_to_skb(vi, rq, page, offset, len, truesize, headroom); > curr_skb = head_skb; > > + if (rq->page_pool) > + skb_mark_for_recycle(curr_skb); > + > if (unlikely(!curr_skb)) > goto err_skb; > while (--num_buf) { > @@ -1509,6 +1538,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > curr_skb = nskb; > head_skb->truesize += nskb->truesize; > num_skb_frags = 0; > + if (rq->page_pool) > + skb_mark_for_recycle(curr_skb); > } > if (curr_skb != head_skb) { > head_skb->data_len += len; > @@ -1517,7 +1548,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > } > offset = buf - page_address(page); > if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) { > - put_page(page); > + virtnet_put_page(rq, page); > skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1, > len, truesize); > } else { > @@ -1530,7 +1561,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > return head_skb; > > err_skb: > - put_page(page); > + virtnet_put_page(rq, page); > mergeable_buf_free(rq, num_buf, dev, stats); > > err_buf: > @@ -1737,31 +1768,40 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, > * disabled GSO for XDP, it won't be a big issue. > */ > len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room); > - if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp))) > - return -ENOMEM; > + if (rq->page_pool) { > + struct page *page; > > - buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; > - buf += headroom; /* advance address leaving hole at front of pkt */ > - get_page(alloc_frag->page); > - alloc_frag->offset += len + room; > - hole = alloc_frag->size - alloc_frag->offset; > - if (hole < len + room) { > - /* To avoid internal fragmentation, if there is very likely not > - * enough space for another buffer, add the remaining space to > - * the current buffer. > - * XDP core assumes that frame_size of xdp_buff and the length > - * of the frag are PAGE_SIZE, so we disable the hole mechanism. > - */ > - if (!headroom) > - len += hole; > - alloc_frag->offset += hole; > - } > + page = page_pool_dev_alloc_pages(rq->page_pool); > + if (unlikely(!page)) > + return -ENOMEM; > + buf = (char *)page_address(page); > + buf += headroom; /* advance address leaving hole at front of pkt */ > + } else { > + if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp))) > + return -ENOMEM; > > + buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; > + buf += headroom; /* advance address leaving hole at front of pkt */ > + get_page(alloc_frag->page); > + alloc_frag->offset += len + room; > + hole = alloc_frag->size - alloc_frag->offset; > + if (hole < len + room) { > + /* To avoid internal fragmentation, if there is very likely not > + * enough space for another buffer, add the remaining space to > + * the current buffer. > + * XDP core assumes that frame_size of xdp_buff and the length > + * of the frag are PAGE_SIZE, so we disable the hole mechanism. > + */ > + if (!headroom) > + len += hole; > + alloc_frag->offset += hole; > + } > + } > sg_init_one(rq->sg, buf, len); > ctx = mergeable_len_to_ctx(len + room, headroom); > err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp); > if (err < 0) > - put_page(virt_to_head_page(buf)); > + virtnet_put_page(rq, virt_to_head_page(buf)); > > return err; > } > @@ -1994,8 +2034,15 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index) > if (err < 0) > return err; > > - err = xdp_rxq_info_reg_mem_model(&vi->rq[qp_index].xdp_rxq, > - MEM_TYPE_PAGE_SHARED, NULL); > + if (vi->rq[qp_index].page_pool) > + err = xdp_rxq_info_reg_mem_model(&vi->rq[qp_index].xdp_rxq, > + MEM_TYPE_PAGE_POOL, > + vi->rq[qp_index].page_pool); > + else > + err = xdp_rxq_info_reg_mem_model(&vi->rq[qp_index].xdp_rxq, > + MEM_TYPE_PAGE_SHARED, > + NULL); > + > if (err < 0) > goto err_xdp_reg_mem_model; > > @@ -2951,6 +2998,7 @@ static void virtnet_get_strings(struct net_device *dev, u32 stringset, u8 *data) > ethtool_sprintf(&p, "tx_queue_%u_%s", i, > virtnet_sq_stats_desc[j].desc); > } > + page_pool_ethtool_stats_get_strings(p); > break; > } > } > @@ -2962,12 +3010,30 @@ static int virtnet_get_sset_count(struct net_device *dev, int sset) > switch (sset) { > case ETH_SS_STATS: > return vi->curr_queue_pairs * (VIRTNET_RQ_STATS_LEN + > - VIRTNET_SQ_STATS_LEN); > + VIRTNET_SQ_STATS_LEN + > + (page_pool_enabled && vi->mergeable_rx_bufs ? > + page_pool_ethtool_stats_get_count() : 0)); > default: > return -EOPNOTSUPP; > } > } > > +static void virtnet_get_page_pool_stats(struct net_device *dev, u64 *data) > +{ > +#ifdef CONFIG_PAGE_POOL_STATS > + struct virtnet_info *vi = netdev_priv(dev); > + struct page_pool_stats pp_stats = {}; > + int i; > + > + for (i = 0; i < vi->curr_queue_pairs; i++) { > + if (!vi->rq[i].page_pool) > + continue; > + page_pool_get_stats(vi->rq[i].page_pool, &pp_stats); > + } > + page_pool_ethtool_stats_get(data, &pp_stats); > +#endif /* CONFIG_PAGE_POOL_STATS */ > +} > + > static void virtnet_get_ethtool_stats(struct net_device *dev, > struct ethtool_stats *stats, u64 *data) > { > @@ -3003,6 +3069,8 @@ static void virtnet_get_ethtool_stats(struct net_device *dev, > } while (u64_stats_fetch_retry(&sq->stats.syncp, start)); > idx += VIRTNET_SQ_STATS_LEN; > } > + > + virtnet_get_page_pool_stats(dev, &data[idx]); > } > > static void virtnet_get_channels(struct net_device *dev, > @@ -3623,6 +3691,8 @@ static void virtnet_free_queues(struct virtnet_info *vi) > for (i = 0; i < vi->max_queue_pairs; i++) { > __netif_napi_del(&vi->rq[i].napi); > __netif_napi_del(&vi->sq[i].napi); > + if (vi->rq[i].page_pool) > + page_pool_destroy(vi->rq[i].page_pool); > } > > /* We called __netif_napi_del(), > @@ -3679,12 +3749,19 @@ static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf) > struct virtnet_info *vi = vq->vdev->priv; > int i = vq2rxq(vq); > > - if (vi->mergeable_rx_bufs) > - put_page(virt_to_head_page(buf)); > - else if (vi->big_packets) > + if (vi->mergeable_rx_bufs) { > + if (vi->rq[i].page_pool) { > + page_pool_put_full_page(vi->rq[i].page_pool, > + virt_to_head_page(buf), > + true); > + } else { > + put_page(virt_to_head_page(buf)); > + } > + } else if (vi->big_packets) { > give_pages(&vi->rq[i], buf); > - else > + } else { > put_page(virt_to_head_page(buf)); > + } > } > > static void free_unused_bufs(struct virtnet_info *vi) > @@ -3718,6 +3795,26 @@ static void virtnet_del_vqs(struct virtnet_info *vi) > virtnet_free_queues(vi); > } > > +static void virtnet_alloc_page_pool(struct receive_queue *rq) > +{ > + struct virtio_device *vdev = rq->vq->vdev; > + > + struct page_pool_params pp_params = { > + .order = 0, > + .pool_size = rq->vq->num_max, > + .nid = dev_to_node(vdev->dev.parent), > + .dev = vdev->dev.parent, > + .offset = 0, > + }; > + > + rq->page_pool = page_pool_create(&pp_params); > + if (IS_ERR(rq->page_pool)) { > + dev_warn(&vdev->dev, "page pool creation failed: %ld\n", > + PTR_ERR(rq->page_pool)); > + rq->page_pool = NULL; > + } > +} > + > /* How large should a single buffer be so a queue full of these can fit at > * least one full packet? > * Logic below assumes the mergeable buffer header is used. > @@ -3801,6 +3898,13 @@ static int virtnet_find_vqs(struct virtnet_info *vi) > vi->rq[i].vq = vqs[rxq2vq(i)]; > vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq); > vi->sq[i].vq = vqs[txq2vq(i)]; > + > + if (page_pool_enabled && vi->mergeable_rx_bufs) > + virtnet_alloc_page_pool(&vi->rq[i]); > + else > + dev_warn(&vi->vdev->dev, > + "page pool only support mergeable mode\n"); > + > } > > /* run here: ret == 0. */ > -- > 2.31.1
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