From: jmaloy@redhat.com
To: netdev@vger.kernel.org, davem@davemloft.net
Cc: kuba@kernel.org, passt-dev@passt.top, jmaloy@redhat.com,
sbrivio@redhat.com, lvivier@redhat.com, dgibson@redhat.com,
eric.dumazet@gmail.com, edumazet@google.com
Subject: [net-next 1/2] tcp: add support for SO_PEEK_OFF socket option
Date: Sat, 6 Apr 2024 14:21:06 -0400 [thread overview]
Message-ID: <20240406182107.261472-2-jmaloy@redhat.com> (raw)
In-Reply-To: <20240406182107.261472-1-jmaloy@redhat.com>
From: Jon Maloy <jmaloy@redhat.com>
When reading received messages from a socket with MSG_PEEK, we may want
to read the contents with an offset, like we can do with pread/preadv()
when reading files. Currently, it is not possible to do that.
In this commit, we add support for the SO_PEEK_OFF socket option for TCP,
in a similar way it is done for Unix Domain sockets.
In the iperf3 log examples shown below, we can observe a throughput
improvement of 15-20 % in the direction host->namespace when using the
protocol splicer 'pasta' (https://passt.top).
This is a consistent result.
pasta(1) and passt(1) implement user-mode networking for network
namespaces (containers) and virtual machines by means of a translation
layer between Layer-2 network interface and native Layer-4 sockets
(TCP, UDP, ICMP/ICMPv6 echo).
Received, pending TCP data to the container/guest is kept in kernel
buffers until acknowledged, so the tool routinely needs to fetch new
data from socket, skipping data that was already sent.
At the moment this is implemented using a dummy buffer passed to
recvmsg(). With this change, we don't need a dummy buffer and the
related buffer copy (copy_to_user()) anymore.
passt and pasta are supported in KubeVirt and libvirt/qemu.
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF not supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 44822
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 44832
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.02 GBytes 8.78 Gbits/sec
[ 5] 1.00-2.00 sec 1.06 GBytes 9.08 Gbits/sec
[ 5] 2.00-3.00 sec 1.07 GBytes 9.15 Gbits/sec
[ 5] 3.00-4.00 sec 1.10 GBytes 9.46 Gbits/sec
[ 5] 4.00-5.00 sec 1.03 GBytes 8.85 Gbits/sec
[ 5] 5.00-6.00 sec 1.10 GBytes 9.44 Gbits/sec
[ 5] 6.00-7.00 sec 1.11 GBytes 9.56 Gbits/sec
[ 5] 7.00-8.00 sec 1.07 GBytes 9.20 Gbits/sec
[ 5] 8.00-9.00 sec 667 MBytes 5.59 Gbits/sec
[ 5] 9.00-10.00 sec 1.03 GBytes 8.83 Gbits/sec
[ 5] 10.00-10.04 sec 30.1 MBytes 6.36 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 10.3 GBytes 8.78 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
jmaloy@freyr:~/passt#
logout
[ perf record: Woken up 23 times to write data ]
[ perf record: Captured and wrote 5.696 MB perf.data (35580 samples) ]
jmaloy@freyr:~/passt$
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 52084
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 52098
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.32 GBytes 11.3 Gbits/sec
[ 5] 1.00-2.00 sec 1.19 GBytes 10.2 Gbits/sec
[ 5] 2.00-3.00 sec 1.26 GBytes 10.8 Gbits/sec
[ 5] 3.00-4.00 sec 1.36 GBytes 11.7 Gbits/sec
[ 5] 4.00-5.00 sec 1.33 GBytes 11.4 Gbits/sec
[ 5] 5.00-6.00 sec 1.21 GBytes 10.4 Gbits/sec
[ 5] 6.00-7.00 sec 1.31 GBytes 11.2 Gbits/sec
[ 5] 7.00-8.00 sec 1.25 GBytes 10.7 Gbits/sec
[ 5] 8.00-9.00 sec 1.33 GBytes 11.5 Gbits/sec
[ 5] 9.00-10.00 sec 1.24 GBytes 10.7 Gbits/sec
[ 5] 10.00-10.04 sec 56.0 MBytes 12.1 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 12.9 GBytes 11.0 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
logout
[ perf record: Woken up 20 times to write data ]
[ perf record: Captured and wrote 5.040 MB perf.data (33411 samples) ]
jmaloy@freyr:~/passt$
The perf record confirms this result. Below, we can observe that the
CPU spends significantly less time in the function ____sys_recvmsg()
when we have offset support.
Without offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
46.32% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
With offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
28.12% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
v3: - Applied changes suggested by Stefano Brivio and Paolo Abeni
v4: - Same as v3. Posting was delayed because I first had to debug
an issue that turned out to not be directly related to this
change. See next commit in this series.
---
net/ipv4/af_inet.c | 1 +
net/ipv4/tcp.c | 16 ++++++++++------
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 55bd72997b31..a7cfeda28bb2 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1072,6 +1072,7 @@ const struct proto_ops inet_stream_ops = {
#endif
.splice_eof = inet_splice_eof,
.splice_read = tcp_splice_read,
+ .set_peek_off = sk_set_peek_off,
.read_sock = tcp_read_sock,
.read_skb = tcp_read_skb,
.sendmsg_locked = tcp_sendmsg_locked,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 92ee60492314..c0d6fd576d32 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1416,8 +1416,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2328,6 +2326,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2361,7 +2360,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2464,11 +2464,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2509,7 +2509,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3010,6 +3013,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
@@ -1416,8 +1416,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2328,6 +2326,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2361,7 +2360,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2464,11 +2464,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2509,7 +2509,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3010,6 +3013,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
2.42.0
next prev parent reply other threads:[~2024-04-06 18:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-06 18:21 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option jmaloy
2024-04-06 18:21 ` jmaloy [this message]
2024-04-08 9:46 ` [net-next 1/2] " Eric Dumazet
2024-04-06 18:21 ` [net-next 2/2] tcp: correct handling of extreme menory squeeze jmaloy
2024-04-06 16:37 ` Eric Dumazet
2024-04-07 4:52 ` Jason Xing
2024-04-07 5:51 ` Menglong Dong
2024-04-08 11:01 ` Jon Maloy
2024-04-08 8:03 ` Eric Dumazet
2024-04-08 11:13 ` Jon Maloy
-- strict thread matches above, loose matches on Subject: below --
2024-04-03 22:58 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option Jon Maloy
2024-04-03 22:58 ` [net-next 1/2] " Jon Maloy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240406182107.261472-2-jmaloy@redhat.com \
--to=jmaloy@redhat.com \
--cc=davem@davemloft.net \
--cc=dgibson@redhat.com \
--cc=edumazet@google.com \
--cc=eric.dumazet@gmail.com \
--cc=kuba@kernel.org \
--cc=lvivier@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=passt-dev@passt.top \
--cc=sbrivio@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://passt.top/passt
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for IMAP folder(s).