From 8eb77cc73977d88787b37c92831b1c242e035396 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Tue, 12 Jul 2022 21:52:25 +0100 Subject: [PATCH] ipv4: avoid partial copy for zc Even when zerocopy transmission is requested and possible, __ip_append_data() will still copy a small chunk of data just because it allocated some extra linear space (e.g. 148 bytes). It wastes CPU cycles on copy and iter manipulations and also misalignes potentially aligned data. Avoid such copies. And as a bonus we can allocate smaller skb. Signed-off-by: Pavel Begunkov Signed-off-by: Jakub Kicinski --- net/ipv4/ip_output.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 00b4bf2..581d1e2 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -969,7 +969,6 @@ static int __ip_append_data(struct sock *sk, struct inet_sock *inet = inet_sk(sk); struct ubuf_info *uarg = NULL; struct sk_buff *skb; - struct ip_options *opt = cork->opt; int hh_len; int exthdrlen; @@ -977,6 +976,7 @@ static int __ip_append_data(struct sock *sk, int copy; int err; int offset = 0; + bool zc = false; unsigned int maxfraglen, fragheaderlen, maxnonfragsize; int csummode = CHECKSUM_NONE; struct rtable *rt = (struct rtable *)cork->dst; @@ -1025,6 +1025,7 @@ static int __ip_append_data(struct sock *sk, if (rt->dst.dev->features & NETIF_F_SG && csummode == CHECKSUM_PARTIAL) { paged = true; + zc = true; } else { uarg->zerocopy = 0; skb_zcopy_set(skb, uarg, &extra_uref); @@ -1091,9 +1092,12 @@ alloc_new_skb: (fraglen + alloc_extra < SKB_MAX_ALLOC || !(rt->dst.dev->features & NETIF_F_SG))) alloclen = fraglen; - else { + else if (!zc) { alloclen = min_t(int, fraglen, MAX_HEADER); pagedlen = fraglen - alloclen; + } else { + alloclen = fragheaderlen + transhdrlen; + pagedlen = datalen - transhdrlen; } alloclen += alloc_extra; -- 2.7.4