Eric Dumazet a36703d08c virtio_net: Do not pull payload in skb->head ... [ Upstream commit 0f6925b3e8 ] Xuan Zhuo reported that commit 3226b158e6 ("net: avoid 32 x truesize under-estimation for tiny skbs") brought a ~10% performance drop. The reason for the performance drop was that GRO was forced to chain sk_buff (using skb_shinfo(skb)->frag_list), which uses more memory but also cause packet consumers to go over a lot of overhead handling all the tiny skbs. It turns out that virtio_net page_to_skb() has a wrong strategy : It allocates skbs with GOOD_COPY_LEN (128) bytes in skb->head, then copies 128 bytes from the page, before feeding the packet to GRO stack. This was suboptimal before commit 3226b158e6 ("net: avoid 32 x truesize under-estimation for tiny skbs") because GRO was using 2 frags per MSS, meaning we were not packing MSS with 100% efficiency. Fix is to pull only the ethernet header in page_to_skb() Then, we change virtio_net_hdr_to_skb() to pull the missing headers, instead of assuming they were already pulled by callers. This fixes the performance regression, but could also allow virtio_net to accept packets with more than 128bytes of headers. Many thanks to Xuan Zhuo for his report, and his tests/help. Fixes: 3226b158e6 ("net: avoid 32 x truesize under-estimation for tiny skbs") Reported-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Link: https://www.spinics.net/lists/netdev/msg731397.html Co-Developed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: virtualization@lists.linux-foundation.org Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-05-22 11:40:52 +02:00
..
acpi	ACPI: scan: Use unique number for instance_no	2021-03-30 14:32:06 +02:00
asm-generic	static_call: Allow module use without exposing static_call_key	2021-03-30 14:31:53 +02:00
clocksource
crypto	crypto: poly1305 - fix poly1305_core_setkey() declaration	2021-05-14 09:50:13 +02:00
drm	drm/dp/mst: Export drm_dp_get_vc_payload_bw()	2021-02-10 09:29:18 +01:00
dt-bindings	ASoC: dt-bindings: lpass: Fix and common up lpass dai ids	2021-02-03 23:28:46 +01:00
keys	security: keys: trusted: fix TPM2 authorizations	2021-05-14 09:50:20 +02:00
kunit
kvm
linux	virtio_net: Do not pull payload in skb->head	2021-05-22 11:40:52 +02:00
math-emu
media	media: v4l2-ctrls: fix reference to freed memory	2021-05-11 14:47:39 +02:00
memory
misc
net	mm: fix struct page layout on 32-bit systems	2021-05-19 10:13:17 +02:00
pcmcia
ras
rdma	RDMA: Lift ibdev_to_node from rds to common code	2021-02-26 10:12:59 +01:00
scsi	Fix misc new gcc warnings	2021-05-11 14:47:36 +02:00
soc	net: dsa: felix: implement port flushing on .phylink_mac_link_down	2021-02-17 11:02:27 +01:00
sound	ALSA: hda: intel-nhlt: verify config type	2021-03-09 11:11:14 +01:00
target	scsi: target: core: Add cmd length set before cmd complete	2021-03-17 17:06:25 +01:00
trace	SUNRPC: Remove trace_xprt_transmit_queued	2021-05-19 10:13:03 +02:00
uapi	netfilter: xt_SECMARK: add new revision to fix structure layout	2021-05-19 10:13:06 +02:00
vdso
video
xen	Xen/gntdev: correct error checking in gntdev_map_grant_pages()	2021-02-23 15:53:24 +01:00