This is a note to let you know that I've just added the patch titled
[PATCH 03/28] tcp: allow splice() to build full TSO packets
to the 3.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-allow-splice-to-build-full-tso-packets.patch
and it can be found in the queue-3.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 3aebf9d9bb951e41e6e87aa6a63c1ebe0a4e31b6 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <[email protected]>
Date: Tue, 24 Apr 2012 22:12:06 -0400
Subject: [PATCH 03/28] tcp: allow splice() to build full TSO packets
From: Eric Dumazet <[email protected]>
[ This combines upstream commit
2f53384424251c06038ae612e56231b96ab610ee and the follow-on bug fix
commit 35f9c09fe9c72eb8ca2b8e89a593e1c151f28fc2 ]
vmsplice()/splice(pipe, socket) call do_tcp_sendpages() one page at a
time, adding at most 4096 bytes to an skb. (assuming PAGE_SIZE=4096)
The call to tcp_push() at the end of do_tcp_sendpages() forces an
immediate xmit when pipe is not already filled, and tso_fragment() try
to split these skb to MSS multiples.
4096 bytes are usually split in a skb with 2 MSS, and a remaining
sub-mss skb (assuming MTU=1500)
This makes slow start suboptimal because many small frames are sent to
qdisc/driver layers instead of big ones (constrained by cwnd and packets
in flight of course)
In fact, applications using sendmsg() (adding an additional memory copy)
instead of vmsplice()/splice()/sendfile() are a bit faster because of
this anomaly, especially if serving small files in environments with
large initial [c]wnd.
Call tcp_push() only if MSG_MORE is not set in the flags parameter.
This bit is automatically provided by splice() internals but for the
last page, or on all pages if user specified SPLICE_F_MORE splice()
flag.
In some workloads, this can reduce number of sent logical packets by an
order of magnitude, making zero-copy TCP actually faster than
one-copy :)
Reported-by: Tom Herbert <[email protected]>
Cc: Nandita Dukkipati <[email protected]>
Cc: Neal Cardwell <[email protected]>
Cc: Tom Herbert <[email protected]>
Cc: Yuchung Cheng <[email protected]>
Cc: H.K. Jerry Chu <[email protected]>
Cc: Maciej Żenczykowski <[email protected]>
Cc: Mahesh Bandewar <[email protected]>
Cc: Ilpo Järvinen <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/splice.c | 5 ++++-
include/linux/socket.h | 2 +-
net/ipv4/tcp.c | 2 +-
net/socket.c | 6 +++---
4 files changed, 9 insertions(+), 6 deletions(-)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -30,6 +30,7 @@
#include <linux/uio.h>
#include <linux/security.h>
#include <linux/gfp.h>
+#include <linux/socket.h>
/*
* Attempt to steal a page from a pipe buffer. This should perhaps go into
@@ -690,7 +691,9 @@ static int pipe_to_sendpage(struct pipe_
if (!likely(file->f_op && file->f_op->sendpage))
return -EINVAL;
- more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
+ more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
+ if (sd->len < sd->total_len)
+ more |= MSG_SENDPAGE_NOTLAST;
return file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -265,7 +265,7 @@ struct ucred {
#define MSG_NOSIGNAL 0x4000 /* Do not generate SIGPIPE */
#define MSG_MORE 0x8000 /* Sender will send more */
#define MSG_WAITFORONE 0x10000 /* recvmmsg(): block until 1+ packets avail */
-
+#define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last
page */
#define MSG_EOF MSG_FIN
#define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exit for file
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -858,7 +858,7 @@ wait_for_memory:
}
out:
- if (copied)
+ if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
tcp_push(sk, flags, mss_now, tp->nonagle);
return copied;
--- a/net/socket.c
+++ b/net/socket.c
@@ -811,9 +811,9 @@ static ssize_t sock_sendpage(struct file
sock = file->private_data;
- flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
- if (more)
- flags |= MSG_MORE;
+ flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
+ /* more is a combination of MSG_MORE and MSG_SENDPAGE_NOTLAST */
+ flags |= more;
return kernel_sendpage(sock, page, offset, size, flags);
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.3/net-fix-a-race-in-sock_queue_err_skb.patch
queue-3.3/tcp-allow-splice-to-build-full-tso-packets.patch
queue-3.3/net-fix-proc-net-dev-regression.patch
queue-3.3/tcp-restore-correct-limit.patch
queue-3.3/net-allow-pskb_expand_head-to-get-maximum-tailroom.patch
queue-3.3/net-smsc911x-fix-skb-handling-in-receive-path.patch
queue-3.3/tcp-avoid-order-1-allocations-on-wifi-and-tx-path.patch
queue-3.3/netlink-fix-races-after-skb-queueing.patch
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