Eric Dumazet
2021-Apr-07 17:13 UTC
[PATCH net-next] virtio-net: page_to_skb() use build_skb when there's sufficient tailroom
On 4/7/21 7:49 AM, Xuan Zhuo wrote:> In page_to_skb(), if we have enough tailroom to save skb_shared_info, we > can use build_skb to create skb directly. No need to alloc for > additional space. And it can save a 'frags slot', which is very friendly > to GRO. > > Here, if the payload of the received package is too small (less than > GOOD_COPY_LEN), we still choose to copy it directly to the space got by > napi_alloc_skb. So we can reuse these pages. > > Testing Machine: > The four queues of the network card are bound to the cpu1. > > Test command: > for ((i=0;i<5;++i)); do sockperf tp --ip 192.168.122.64 -m 1000 -t 150& done > > The size of the udp package is 1000, so in the case of this patch, there > will always be enough tailroom to use build_skb. The sent udp packet > will be discarded because there is no port to receive it. The irqsoftd > of the machine is 100%, we observe the received quantity displayed by > sar -n DEV 1: > > no build_skb: 956864.00 rxpck/s > build_skb: 1158465.00 rxpck/s > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > Suggested-by: Jason Wang <jasowang at redhat.com> > ---This will generate merge conflicts. Please wait that commit 0f6925b3e8da ("virtio_net: Do not pull payload in skb->head") has reached net-next. Also are we sure pages are always writable, and not shared ?