Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Fri, 31 Mar 2023 17:01:54 +0800, Jason Wang wrote:
> On Tue, Mar 28, 2023 at 8:04 PM Xuan Zhuo wrote:
> >
> > In the xdp implementation of virtio-net mergeable, it always checks
> > whether two page is used and a page is selected to release. This is
> > complicated for the processing of action, and be careful.
> >
> > In the entire process, we have such principles:
> > * If xdp_page is used (PASS, TX, Redirect), then we release the old
> > page.
> > * If it is a drop case, we will release two. The old page obtained from
> > buf is release inside err_xdp, and xdp_page needs be relased by us.
> >
> > But in fact, when we allocate a new page, we can release the old page
> > immediately. Then just one is using, we just need to release the new
> > page for drop case. On the drop path, err_xdp will release the variable
> > "page", so we only need to let "page" point to the new xdp_page in
> > advance.
> >
> > Signed-off-by: Xuan Zhuo
> > ---
> > drivers/net/virtio_net.c | 15 ++-
> > 1 file changed, 6 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index e2560b6f7980..4d2bf1ce0730 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (!xdp_page)
> > goto err_xdp;
> > offset = VIRTIO_XDP_HEADROOM;
> > +
> > + put_page(page);
> > + page = xdp_page;
> > } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> > xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> > sizeof(struct
> > skb_shared_info));
> > @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> >page_address(page) + offset, len);
> > frame_sz = PAGE_SIZE;
> > offset = VIRTIO_XDP_HEADROOM;
> > +
> > + put_page(page);
> > + page = xdp_page;
> > } else {
> > xdp_page = page;
> > }
>
> While at this I would go a little further, just remove the above
> assignment then we can use:
>
> data = page_address(page) + offset;
>
> Which seems cleaner?
I will try.
Thanks.
>
> Thanks
>
> > @@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (unlikely(!head_skb))
> > goto err_xdp_frags;
> >
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > return head_skb;
> > case XDP_TX:
> > @@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > goto err_xdp_frags;
> > }
> > *xdp_xmit |= VIRTIO_XDP_TX;
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > goto xdp_xmit;
> > case XDP_REDIRECT:
> > @@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (err)
> > goto err_xdp_frags;
> > *xdp_xmit |= VIRTIO_XDP_REDIR;
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > goto xdp_xmit;
> > default:
> > @@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > goto err_xdp_frags;
> > }
> > err_xdp_frags:
> > - if (unlikely(xdp_page != page))
> > - __free_pages(xdp_page, 0);
> > -
> > if (xdp_buff_has_frags()) {
> > shinfo = xdp_get_shared_info_from_buff();
> > for (i = 0; i < shinfo->nr_frags; i++) {
> > --
> > 2.32.0.3.g01195cf9f
> >
>
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Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Tue, Mar 28, 2023 at 8:04 PM Xuan Zhuo wrote:
>
> In the xdp implementation of virtio-net mergeable, it always checks
> whether two page is used and a page is selected to release. This is
> complicated for the processing of action, and be careful.
>
> In the entire process, we have such principles:
> * If xdp_page is used (PASS, TX, Redirect), then we release the old
> page.
> * If it is a drop case, we will release two. The old page obtained from
> buf is release inside err_xdp, and xdp_page needs be relased by us.
>
> But in fact, when we allocate a new page, we can release the old page
> immediately. Then just one is using, we just need to release the new
> page for drop case. On the drop path, err_xdp will release the variable
> "page", so we only need to let "page" point to the new xdp_page in
> advance.
>
> Signed-off-by: Xuan Zhuo
> ---
> drivers/net/virtio_net.c | 15 ++-
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e2560b6f7980..4d2bf1ce0730 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> if (!xdp_page)
> goto err_xdp;
> offset = VIRTIO_XDP_HEADROOM;
> +
> + put_page(page);
> + page = xdp_page;
> } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> sizeof(struct
> skb_shared_info));
> @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
>page_address(page) + offset, len);
> frame_sz = PAGE_SIZE;
> offset = VIRTIO_XDP_HEADROOM;
> +
> + put_page(page);
> + page = xdp_page;
> } else {
> xdp_page = page;
> }
While at this I would go a little further, just remove the above
assignment then we can use:
data = page_address(page) + offset;
Which seems cleaner?
Thanks
> @@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> if (unlikely(!head_skb))
> goto err_xdp_frags;
>
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> return head_skb;
> case XDP_TX:
> @@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> goto err_xdp_frags;
> }
> *xdp_xmit |= VIRTIO_XDP_TX;
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> goto xdp_xmit;
> case XDP_REDIRECT:
> @@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> if (err)
> goto err_xdp_frags;
> *xdp_xmit |= VIRTIO_XDP_REDIR;
> - if (unlikely(xdp_page != page))
> - put_page(page);
> rcu_read_unlock();
> goto xdp_xmit;
> default:
> @@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> goto err_xdp_frags;
> }
> err_xdp_frags:
> - if (unlikely(xdp_page != page))
> - __free_pages(xdp_page, 0);
> -
> if (xdp_buff_has_frags()) {
> shinfo = xdp_get_shared_info_from_buff();
> for (i = 0; i < shinfo->nr_frags; i++) {
> --
> 2.32.0.3.g01195cf9f
>
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[PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
In the xdp implementation of virtio-net mergeable, it always checks
whether two page is used and a page is selected to release. This is
complicated for the processing of action, and be careful.
In the entire process, we have such principles:
* If xdp_page is used (PASS, TX, Redirect), then we release the old
page.
* If it is a drop case, we will release two. The old page obtained from
buf is release inside err_xdp, and xdp_page needs be relased by us.
But in fact, when we allocate a new page, we can release the old page
immediately. Then just one is using, we just need to release the new
page for drop case. On the drop path, err_xdp will release the variable
"page", so we only need to let "page" point to the new xdp_page in
advance.
Signed-off-by: Xuan Zhuo
---
drivers/net/virtio_net.c | 15 ++-
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e2560b6f7980..4d2bf1ce0730 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (!xdp_page)
goto err_xdp;
offset = VIRTIO_XDP_HEADROOM;
+
+ put_page(page);
+ page = xdp_page;
} else if (unlikely(headroom < virtnet_get_headroom(vi))) {
xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
sizeof(struct
skb_shared_info));
@@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
page_address(page) + offset, len);
frame_sz = PAGE_SIZE;
offset = VIRTIO_XDP_HEADROOM;
+
+ put_page(page);
+ page = xdp_page;
} else {
xdp_page = page;
}
@@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (unlikely(!head_skb))
goto err_xdp_frags;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
return head_skb;
case XDP_TX:
@@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
goto err_xdp_frags;
}
*xdp_xmit |= VIRTIO_XDP_TX;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
goto xdp_xmit;
case XDP_REDIRECT:
@@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (err)
goto err_xdp_frags;
*xdp_xmit |= VIRTIO_XDP_REDIR;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
goto xdp_xmit;
default:
@@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
goto err_xdp_frags;
}
err_xdp_frags:
- if (unlikely(xdp_page != page))
- __free_pages(xdp_page, 0);
-
if (xdp_buff_has_frags()) {
shinfo = xdp_get_shared_info_from_buff();
for (i = 0; i < shinfo->nr_frags; i++) {
--
2.32.0.3.g01195cf9f
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Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Thu, 23 Mar 2023 13:38:30 +0800, Jason Wang wrote:
> On Thu, Mar 23, 2023 at 9:43 AM Xuan Zhuo wrote:
> >
> > On Wed, 22 Mar 2023 16:22:18 +0800, Yunsheng Lin
> > wrote:
> > > On 2023/3/22 11:03, Xuan Zhuo wrote:
> > > > In the xdp implementation of virtio-net mergeable, it always checks
> > > > whether two page is used and a page is selected to release. This is
> > > > complicated for the processing of action, and be careful.
> > > >
> > > > In the entire process, we have such principles:
> > > > * If xdp_page is used (PASS, TX, Redirect), then we release the old
> > > > page.
> > > > * If it is a drop case, we will release two. The old page obtained from
> > > > buf is release inside err_xdp, and xdp_page needs be relased by us.
> > > >
> > > > But in fact, when we allocate a new page, we can release the old page
> > > > immediately. Then just one is using, we just need to release the new
> > > > page for drop case. On the drop path, err_xdp will release the variable
> > > > "page", so we only need to let "page" point to the new xdp_page in
> > > > advance.
> > > >
> > > > Signed-off-by: Xuan Zhuo
> > > > ---
> > > > drivers/net/virtio_net.c | 15 ++-
> > > > 1 file changed, 6 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index e2560b6f7980..4d2bf1ce0730 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> > > > net_device *dev,
> > > > if (!xdp_page)
> > > > goto err_xdp;
> > > > offset = VIRTIO_XDP_HEADROOM;
> > > > +
> > > > + put_page(page);
> > >
> > > the error handling of xdp_linearize_page() does not seems self contained.
> > > Does it not seem better：
> > > 1. if xdp_linearize_page() succesed, call put_page() for first buffer just
> > >as put_page() is call for other buffer
> > > 2. or call virtqueue_get_buf() and put_page() for all the buffer of the
> > > packet
> > >so the error handling is not needed outside the virtqueue_get_buf().
> > >
> > > In that case, it seems we can just do below without xdp_page:
> > > page = xdp_linearize_page(rq, num_buf, page, ...);
> >
> >
> > This does look better.
> >
> > In fact, we already have vq reset, we can load XDP based on vq reset.
> > In this way, we can run without xdp_linearize_page.
>
> The goal is to try our best not to drop packets, so I think it's
> better to keep it.
Yes. vq reset may drop some packets.
Thanks.
>
> Thanks
>
> >
> >
> > >
> > >
> > > > + page = xdp_page;
> > > > } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> > > > xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> > > > sizeof(struct
> > > > skb_shared_info));
> > > > @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> > > > net_device *dev,
> > > >page_address(page) + offset, len);
> > > > frame_sz = PAGE_SIZE;
> > > > offset = VIRTIO_XDP_HEADROOM;
> > > > +
> > > > + put_page(page);
> > > > + page = xdp_page;
> > >
> > > It seems we can limit the scope of xdp_page in this "else if" block.
> > >
> > > > } else {
> > > > xdp_page = page;
> > > > }
> > >
> > > It seems the above else block is not needed anymore.
> >
> > Yes, the follow-up patch has this optimization.
> >
> >
> > >
> > > > @@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
> > > > net_device *dev,
> > > > if (unlikely(!head_skb))
> > > > goto err_xdp_frags;
> > > >
> > > > - if (unlikely(xdp_page != page))
> > > > - put_page(page);
> > > > rcu_read_unlock();
> > > > return head_skb;
> > > > case XDP_TX:
> > > > @@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
> > > > net_device *dev,
> > > > goto err_xdp_frags;
> > > > }
> > > > *xdp_xmit |= VIRTIO_XDP_TX;
> > > > - if (unlikely(xdp_page != page))
> > > > - put_page(page);
> > > > rcu_read_unlock();
> > > > goto xdp_xmit;
> > > > case XDP_REDIRECT:
> > > > @@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
> > > > net_device *dev,
> > > > if (err)
> > > > goto err_xdp_frags;
> > > > *xdp_xmit |= VIRTIO_XDP_REDIR;
> > > > - if (unlikely(xdp_page != page))
> > > > - put_page(page);
> > > >
Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Thu, Mar 23, 2023 at 9:43 AM Xuan Zhuo wrote:
>
> On Wed, 22 Mar 2023 16:22:18 +0800, Yunsheng Lin
> wrote:
> > On 2023/3/22 11:03, Xuan Zhuo wrote:
> > > In the xdp implementation of virtio-net mergeable, it always checks
> > > whether two page is used and a page is selected to release. This is
> > > complicated for the processing of action, and be careful.
> > >
> > > In the entire process, we have such principles:
> > > * If xdp_page is used (PASS, TX, Redirect), then we release the old
> > > page.
> > > * If it is a drop case, we will release two. The old page obtained from
> > > buf is release inside err_xdp, and xdp_page needs be relased by us.
> > >
> > > But in fact, when we allocate a new page, we can release the old page
> > > immediately. Then just one is using, we just need to release the new
> > > page for drop case. On the drop path, err_xdp will release the variable
> > > "page", so we only need to let "page" point to the new xdp_page in
> > > advance.
> > >
> > > Signed-off-by: Xuan Zhuo
> > > ---
> > > drivers/net/virtio_net.c | 15 ++-
> > > 1 file changed, 6 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index e2560b6f7980..4d2bf1ce0730 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > > if (!xdp_page)
> > > goto err_xdp;
> > > offset = VIRTIO_XDP_HEADROOM;
> > > +
> > > + put_page(page);
> >
> > the error handling of xdp_linearize_page() does not seems self contained.
> > Does it not seem better：
> > 1. if xdp_linearize_page() succesed, call put_page() for first buffer just
> >as put_page() is call for other buffer
> > 2. or call virtqueue_get_buf() and put_page() for all the buffer of the
> > packet
> >so the error handling is not needed outside the virtqueue_get_buf().
> >
> > In that case, it seems we can just do below without xdp_page:
> > page = xdp_linearize_page(rq, num_buf, page, ...);
>
>
> This does look better.
>
> In fact, we already have vq reset, we can load XDP based on vq reset.
> In this way, we can run without xdp_linearize_page.
The goal is to try our best not to drop packets, so I think it's
better to keep it.
Thanks
>
>
> >
> >
> > > + page = xdp_page;
> > > } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> > > xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> > > sizeof(struct
> > > skb_shared_info));
> > > @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > >page_address(page) + offset, len);
> > > frame_sz = PAGE_SIZE;
> > > offset = VIRTIO_XDP_HEADROOM;
> > > +
> > > + put_page(page);
> > > + page = xdp_page;
> >
> > It seems we can limit the scope of xdp_page in this "else if" block.
> >
> > > } else {
> > > xdp_page = page;
> > > }
> >
> > It seems the above else block is not needed anymore.
>
> Yes, the follow-up patch has this optimization.
>
>
> >
> > > @@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > > if (unlikely(!head_skb))
> > > goto err_xdp_frags;
> > >
> > > - if (unlikely(xdp_page != page))
> > > - put_page(page);
> > > rcu_read_unlock();
> > > return head_skb;
> > > case XDP_TX:
> > > @@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > > goto err_xdp_frags;
> > > }
> > > *xdp_xmit |= VIRTIO_XDP_TX;
> > > - if (unlikely(xdp_page != page))
> > > - put_page(page);
> > > rcu_read_unlock();
> > > goto xdp_xmit;
> > > case XDP_REDIRECT:
> > > @@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > > if (err)
> > > goto err_xdp_frags;
> > > *xdp_xmit |= VIRTIO_XDP_REDIR;
> > > - if (unlikely(xdp_page != page))
> > > - put_page(page);
> > > rcu_read_unlock();
> > > goto xdp_xmit;
> > > default:
> > > @@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
> > > net_device *dev,
> > > goto err_xdp_frags;
> > > }
> > > err_xdp_frags:
> > > - if (unlikely(xdp_page != page))
> > > -
Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Thu, 23 Mar 2023 11:38:34 +0800, Yunsheng Lin wrote:
> On 2023/3/23 9:36, Xuan Zhuo wrote:
> > On Wed, 22 Mar 2023 16:22:18 +0800, Yunsheng Lin
> > wrote:
> >> On 2023/3/22 11:03, Xuan Zhuo wrote:
> >>> In the xdp implementation of virtio-net mergeable, it always checks
> >>> whether two page is used and a page is selected to release. This is
> >>> complicated for the processing of action, and be careful.
> >>>
> >>> In the entire process, we have such principles:
> >>> * If xdp_page is used (PASS, TX, Redirect), then we release the old
> >>> page.
> >>> * If it is a drop case, we will release two. The old page obtained from
> >>> buf is release inside err_xdp, and xdp_page needs be relased by us.
> >>>
> >>> But in fact, when we allocate a new page, we can release the old page
> >>> immediately. Then just one is using, we just need to release the new
> >>> page for drop case. On the drop path, err_xdp will release the variable
> >>> "page", so we only need to let "page" point to the new xdp_page in
> >>> advance.
> >>>
> >>> Signed-off-by: Xuan Zhuo
> >>> ---
> >>> drivers/net/virtio_net.c | 15 ++-
> >>> 1 file changed, 6 insertions(+), 9 deletions(-)
> >>>
> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >>> index e2560b6f7980..4d2bf1ce0730 100644
> >>> --- a/drivers/net/virtio_net.c
> >>> +++ b/drivers/net/virtio_net.c
> >>> @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> >>> net_device *dev,
> >>> if (!xdp_page)
> >>> goto err_xdp;
> >>> offset = VIRTIO_XDP_HEADROOM;
> >>> +
> >>> + put_page(page);
> >>
> >> the error handling of xdp_linearize_page() does not seems self contained.
> >> Does it not seem better：
> >> 1. if xdp_linearize_page() succesed, call put_page() for first buffer just
> >>as put_page() is call for other buffer
> >> 2. or call virtqueue_get_buf() and put_page() for all the buffer of the
> >> packet
> >>so the error handling is not needed outside the virtqueue_get_buf().
> >>
> >> In that case, it seems we can just do below without xdp_page:
> >> page = xdp_linearize_page(rq, num_buf, page, ...);
> >
> >
> > This does look better.
> >
> > In fact, we already have vq reset, we can load XDP based on vq reset.
> > In this way, we can run without xdp_linearize_page.
>
> For compatibility, it is still needed, right?
Yes
>
> >
> >
> >>
> >>
> >>> + page = xdp_page;
> >>> } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> >>> xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> >>> sizeof(struct
> >>> skb_shared_info));
> >>> @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> >>> net_device *dev,
> >>> page_address(page) + offset, len);
> >>> frame_sz = PAGE_SIZE;
> >>> offset = VIRTIO_XDP_HEADROOM;
> >>> +
> >>> + put_page(page);
> >>> + page = xdp_page;
> >>
> >> It seems we can limit the scope of xdp_page in this "else if" block.
> >>
> >>> } else {
> >>> xdp_page = page;
> >>> }
> >>
> >> It seems the above else block is not needed anymore.
> >
> > Yes, the follow-up patch has this optimization.
>
> Isn't refoctor patch supposed to be self-contianed too, instead of
> depending on follow-up patch?
I mean that the #2 patch do this.
Thanks.
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Re: [PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
On Wed, 22 Mar 2023 16:22:18 +0800, Yunsheng Lin wrote:
> On 2023/3/22 11:03, Xuan Zhuo wrote:
> > In the xdp implementation of virtio-net mergeable, it always checks
> > whether two page is used and a page is selected to release. This is
> > complicated for the processing of action, and be careful.
> >
> > In the entire process, we have such principles:
> > * If xdp_page is used (PASS, TX, Redirect), then we release the old
> > page.
> > * If it is a drop case, we will release two. The old page obtained from
> > buf is release inside err_xdp, and xdp_page needs be relased by us.
> >
> > But in fact, when we allocate a new page, we can release the old page
> > immediately. Then just one is using, we just need to release the new
> > page for drop case. On the drop path, err_xdp will release the variable
> > "page", so we only need to let "page" point to the new xdp_page in
> > advance.
> >
> > Signed-off-by: Xuan Zhuo
> > ---
> > drivers/net/virtio_net.c | 15 ++-
> > 1 file changed, 6 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index e2560b6f7980..4d2bf1ce0730 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (!xdp_page)
> > goto err_xdp;
> > offset = VIRTIO_XDP_HEADROOM;
> > +
> > + put_page(page);
>
> the error handling of xdp_linearize_page() does not seems self contained.
> Does it not seem better：
> 1. if xdp_linearize_page() succesed, call put_page() for first buffer just
>as put_page() is call for other buffer
> 2. or call virtqueue_get_buf() and put_page() for all the buffer of the packet
>so the error handling is not needed outside the virtqueue_get_buf().
>
> In that case, it seems we can just do below without xdp_page:
> page = xdp_linearize_page(rq, num_buf, page, ...);
This does look better.
In fact, we already have vq reset, we can load XDP based on vq reset.
In this way, we can run without xdp_linearize_page.
>
>
> > + page = xdp_page;
> > } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> > xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
> > sizeof(struct
> > skb_shared_info));
> > @@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> >page_address(page) + offset, len);
> > frame_sz = PAGE_SIZE;
> > offset = VIRTIO_XDP_HEADROOM;
> > +
> > + put_page(page);
> > + page = xdp_page;
>
> It seems we can limit the scope of xdp_page in this "else if" block.
>
> > } else {
> > xdp_page = page;
> > }
>
> It seems the above else block is not needed anymore.
Yes, the follow-up patch has this optimization.
>
> > @@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (unlikely(!head_skb))
> > goto err_xdp_frags;
> >
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > return head_skb;
> > case XDP_TX:
> > @@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > goto err_xdp_frags;
> > }
> > *xdp_xmit |= VIRTIO_XDP_TX;
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > goto xdp_xmit;
> > case XDP_REDIRECT:
> > @@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > if (err)
> > goto err_xdp_frags;
> > *xdp_xmit |= VIRTIO_XDP_REDIR;
> > - if (unlikely(xdp_page != page))
> > - put_page(page);
> > rcu_read_unlock();
> > goto xdp_xmit;
> > default:
> > @@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
> > net_device *dev,
> > goto err_xdp_frags;
> > }
> > err_xdp_frags:
> > - if (unlikely(xdp_page != page))
> > - __free_pages(xdp_page, 0);
>
> It seems __free_pages() and put_page() is used interchangeably here.
> Perhaps using __free_pages() have performance reason? As the comment below:
>
> https://elixir.bootlin.com/linux/v6.3-rc3/source/net/core/page_pool.c#L500
Yes, but now we don't seem to be very good to distinguish it. But I think
it doesn't matter. This logic is rare
[PATCH net-next 1/8] virtio_net: mergeable xdp: put old page immediately
In the xdp implementation of virtio-net mergeable, it always checks
whether two page is used and a page is selected to release. This is
complicated for the processing of action, and be careful.
In the entire process, we have such principles:
* If xdp_page is used (PASS, TX, Redirect), then we release the old
page.
* If it is a drop case, we will release two. The old page obtained from
buf is release inside err_xdp, and xdp_page needs be relased by us.
But in fact, when we allocate a new page, we can release the old page
immediately. Then just one is using, we just need to release the new
page for drop case. On the drop path, err_xdp will release the variable
"page", so we only need to let "page" point to the new xdp_page in
advance.
Signed-off-by: Xuan Zhuo
---
drivers/net/virtio_net.c | 15 ++-
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e2560b6f7980..4d2bf1ce0730 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1245,6 +1245,9 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (!xdp_page)
goto err_xdp;
offset = VIRTIO_XDP_HEADROOM;
+
+ put_page(page);
+ page = xdp_page;
} else if (unlikely(headroom < virtnet_get_headroom(vi))) {
xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
sizeof(struct
skb_shared_info));
@@ -1259,6 +1262,9 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
page_address(page) + offset, len);
frame_sz = PAGE_SIZE;
offset = VIRTIO_XDP_HEADROOM;
+
+ put_page(page);
+ page = xdp_page;
} else {
xdp_page = page;
}
@@ -1278,8 +1284,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (unlikely(!head_skb))
goto err_xdp_frags;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
return head_skb;
case XDP_TX:
@@ -1297,8 +1301,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
goto err_xdp_frags;
}
*xdp_xmit |= VIRTIO_XDP_TX;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
goto xdp_xmit;
case XDP_REDIRECT:
@@ -1307,8 +1309,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
if (err)
goto err_xdp_frags;
*xdp_xmit |= VIRTIO_XDP_REDIR;
- if (unlikely(xdp_page != page))
- put_page(page);
rcu_read_unlock();
goto xdp_xmit;
default:
@@ -1321,9 +1321,6 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
goto err_xdp_frags;
}
err_xdp_frags:
- if (unlikely(xdp_page != page))
- __free_pages(xdp_page, 0);
-
if (xdp_buff_has_frags()) {
shinfo = xdp_get_shared_info_from_buff();
for (i = 0; i < shinfo->nr_frags; i++) {
--
2.32.0.3.g01195cf9f
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