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From: Pavel Begunkov <[email protected]>
To: [email protected], [email protected],
	[email protected]
Cc: "David S . Miller" <[email protected]>,
	Jakub Kicinski <[email protected]>,
	Jonathan Lemon <[email protected]>,
	Willem de Bruijn <[email protected]>,
	Jens Axboe <[email protected]>,
	[email protected], Pavel Begunkov <[email protected]>
Subject: [RFC net-next v3 01/29] ipv4: avoid partial copy for zc
Date: Tue, 28 Jun 2022 19:56:23 +0100	[thread overview]
Message-ID: <31cdb30c440efc9d4cebe196f4dc78d0c1484210.1653992701.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>

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 coies. And as a bonus we can allocate smaller skb.

Signed-off-by: Pavel Begunkov <[email protected]>
---
 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 00b4bf26fd93..581d1e233260 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 @@ static int __ip_append_data(struct sock *sk,
 				 (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;
-- 
2.36.1



  reply	other threads:[~2022-06-28 19:00 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-28 18:56 [RFC net-next v3 00/29] io_uring zerocopy send Pavel Begunkov
2022-06-28 18:56 ` Pavel Begunkov [this message]
2022-06-28 18:56 ` [RFC net-next v3 02/29] ipv6: avoid partial copy for zc Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 03/29] skbuff: add SKBFL_DONT_ORPHAN flag Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 04/29] skbuff: carry external ubuf_info in msghdr Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 05/29] net: bvec specific path in zerocopy_sg_from_iter Pavel Begunkov
2022-06-28 22:52   ` David Ahern
     [not found]     ` <[email protected]>
     [not found]       ` <[email protected]>
2022-07-05 14:03         ` Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 06/29] net: optimise bvec-based zc page referencing Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 07/29] net: don't track pfmemalloc for managed frags Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 08/29] skbuff: don't mix ubuf_info of different types Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 09/29] ipv4/udp: support zc with managed data Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 10/29] ipv6/udp: " Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 11/29] tcp: " Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 12/29] tcp: kill extra io_uring's uarg refcounting Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 13/29] net: let callers provide extra ubuf_info refs Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 14/29] io_uring: opcode independent fixed buf import Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 15/29] io_uring: add zc notification infrastructure Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 16/29] io_uring: cache struct io_notif Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 17/29] io_uring: complete notifiers in tw Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 18/29] io_uring: add notification slot registration Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 19/29] io_uring: rename IORING_OP_FILES_UPDATE Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 20/29] io_uring: add zc notification flush requests Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 21/29] io_uring: wire send zc request type Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 22/29] io_uring: account locked pages for non-fixed zc Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 23/29] io_uring: allow to pass addr into sendzc Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 24/29] io_uring: add rsrc referencing for notifiers Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 25/29] io_uring: sendzc with fixed buffers Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 26/29] io_uring: flush notifiers after sendzc Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 27/29] io_uring: allow to override zc tag on flush Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 28/29] io_uring: batch submission notif referencing Pavel Begunkov
2022-06-28 18:56 ` [RFC net-next v3 29/29] selftests/io_uring: test zerocopy send Pavel Begunkov

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