Messages in this thread | | | Subject | Re: [PATCH net-next 2/5] virtio-net: pack headroom into ctx for mergeable buffer | From | Jason Wang <> | Date | Wed, 19 Jul 2017 10:29:18 +0800 |
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On 2017年07月19日 02:59, Michael S. Tsirkin wrote: > On Mon, Jul 17, 2017 at 08:43:58PM +0800, Jason Wang wrote: >> Pack headroom into ctx, then during XDP set, we could know the size of >> headroom and copy if needed. This is required for avoiding reset on >> XDP. > Not really when XDP is set - it's when buffers are used.
Of course :)
> > virtio-net: pack headroom into ctx for mergeable buffers > > Pack headroom into ctx - this way when we get a buffer we can figure out > the actual headroom that was allocated for the buffer. Will be helpful > to optimize switching between XDP and non-XDP modes which have different > headroom requirements.
Thanks, let me use this as the commit log.
> >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++----- >> 1 file changed, 24 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 1f8c15c..8fae9a8 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -270,6 +270,23 @@ static void skb_xmit_done(struct virtqueue *vq) >> netif_wake_subqueue(vi->dev, vq2txq(vq)); >> } >> >> +#define MRG_CTX_HEADER_SHIFT 22 >> +static void *mergeable_len_to_ctx(unsigned int truesize, >> + unsigned int headroom) >> +{ >> + return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) | truesize); >> +} >> + >> +static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx) >> +{ >> + return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT; >> +} >> + >> +static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx) >> +{ >> + return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1); >> +} >> + >> /* Called from bottom half context */ >> static struct sk_buff *page_to_skb(struct virtnet_info *vi, >> struct receive_queue *rq, >> @@ -639,13 +656,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, >> } >> rcu_read_unlock(); >> >> - if (unlikely(len > (unsigned long)ctx)) { >> + truesize = mergeable_ctx_to_truesize(ctx); >> + if (unlikely(len > truesize)) { >> pr_debug("%s: rx error: len %u exceeds truesize %lu\n", >> dev->name, len, (unsigned long)ctx); >> dev->stats.rx_length_errors++; >> goto err_skb; >> } >> - truesize = (unsigned long)ctx; >> + >> head_skb = page_to_skb(vi, rq, page, offset, len, truesize); >> curr_skb = head_skb; >> >> @@ -665,13 +683,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, >> } >> >> page = virt_to_head_page(buf); >> - if (unlikely(len > (unsigned long)ctx)) { >> + >> + truesize = mergeable_ctx_to_truesize(ctx); >> + if (unlikely(len > truesize)) { >> pr_debug("%s: rx error: len %u exceeds truesize %lu\n", >> dev->name, len, (unsigned long)ctx); >> dev->stats.rx_length_errors++; >> goto err_skb; >> } >> - truesize = (unsigned long)ctx; >> >> num_skb_frags = skb_shinfo(curr_skb)->nr_frags; >> if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) { >> @@ -889,7 +908,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, >> >> buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; >> buf += headroom; /* advance address leaving hole at front of pkt */ >> - ctx = (void *)(unsigned long)len; >> + ctx = mergeable_len_to_ctx(len, headroom); >> get_page(alloc_frag->page); >> alloc_frag->offset += len + headroom; >> hole = alloc_frag->size - alloc_frag->offset; >> -- >> 2.7.4
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