Re: [PATCH net-next 2/5] virtio_net: Add page_pool support to improve performance

[Liang Chen <liangchen.linux@gmail.com>]

On Tue, May 30, 2023 at 9:19 AM Liang Chen <liangchen.linux@gmail.com> wrote:
>
> On Mon, May 29, 2023 at 5:55 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Mon, May 29, 2023 at 03:27:56PM +0800, Liang Chen wrote:
> > > On Sun, May 28, 2023 at 2:20 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >
> > > > 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@gmail.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...
> > > >
> > > >
> > >
> > > Sure, now I believe it makes sense to enable it by default. When the
> > > packet size is very small, it reduces the likelihood of skb
> > > coalescing. But such cases are rare.
> >
> > small packets are rare? These workloads are easy to create actually.
> > Pls try and include benchmark with small packet size.
> >
>
> Sure, Thanks!

Before going ahead and posting v2 patch, I would like to hear more
advice for the cases of small packets. I have done more performance
benchmark with small packets since then. Here is a list of iperf
output,

With PP and PP fragmenting:
256K:   [  5] 505.00-510.00 sec  1.34 GBytes  2.31 Gbits/sec    0    144 KBytes
1K:       [  5]  30.00-35.00  sec  4.63 GBytes  7.95 Gbits/sec    0
223 KBytes
2K:       [  5]  65.00-70.00  sec  8.33 GBytes  14.3 Gbits/sec    0
324 KBytes
4K:       [  5]  30.00-35.00  sec  13.3 GBytes  22.8 Gbits/sec    0
1.08 MBytes
8K:       [  5]  50.00-55.00  sec  18.9 GBytes  32.4 Gbits/sec    0
744 KBytes
16K:     [  5]  25.00-30.00  sec  24.6 GBytes  42.3 Gbits/sec    0    963 KBytes
32K:     [  5]  45.00-50.00  sec  29.8 GBytes  51.2 Gbits/sec    0   1.25 MBytes
64K:     [  5]  35.00-40.00  sec  34.0 GBytes  58.4 Gbits/sec    0   1.70 MBytes
128K:   [  5]  45.00-50.00  sec  36.7 GBytes  63.1 Gbits/sec    0   4.26 MBytes
256K:   [  5]  30.00-35.00  sec  40.0 GBytes  68.8 Gbits/sec    0   3.20 MBytes

Without PP:
256:     [  5] 680.00-685.00 sec  1.57 GBytes  2.69 Gbits/sec    0    359 KBytes
1K:      [  5]  75.00-80.00  sec  5.47 GBytes  9.40 Gbits/sec    0    730 KBytes
2K:      [  5]  65.00-70.00  sec  9.46 GBytes  16.2 Gbits/sec    0   1.99 MBytes
4K:      [  5]  30.00-35.00  sec  14.5 GBytes  25.0 Gbits/sec    0   1.20 MBytes
8K:      [  5]  45.00-50.00  sec  19.9 GBytes  34.1 Gbits/sec    0   1.72 MBytes
16K:    [  5]   5.00-10.00  sec  23.8 GBytes  40.9 Gbits/sec    0   2.90 MBytes
32K:    [  5]  15.00-20.00  sec  28.0 GBytes  48.1 Gbits/sec    0   3.03 MBytes
64K:    [  5]  60.00-65.00  sec  31.8 GBytes  54.6 Gbits/sec    0   3.05 MBytes
128K:  [  5]  45.00-50.00  sec  33.0 GBytes  56.6 Gbits/sec    1   3.03 MBytes
256K:  [  5]  25.00-30.00  sec  34.7 GBytes  59.6 Gbits/sec    0   3.11 MBytes


The major factor contributing to the performance drop is the reduction
of skb coalescing. Additionally, without the page pool, small packets
can still benefit from the allocation of 8 continuous pages by
breaking them down into smaller pieces. This effectively reduces the
frequency of page allocation from the buddy system. For instance, the
arrival of 32 1K packets only triggers one alloc_page call. Therefore,
the benefits of using a page pool are limited in such cases. In fact,
without page pool fragmenting enabled, it can even hinder performance
from this perspective.

Upon further consideration, I tend to believe making page pool the
default option may not be appropriate. As you pointed out, we cannot
simply ignore the performance impact on small packets. Any comments on
this will be much appreciated.


Thanks,
Liang


> > > The usage of page pool for big mode is being evaluated now. Thanks!
> > >
> > > > > ---
> > > > >  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
> > > >
> >