From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755803Ab2F2Oyy (ORCPT ); Fri, 29 Jun 2012 10:54:54 -0400 Received: from zimbra.linbit.com ([212.69.161.123]:57317 "EHLO zimbra.linbit.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755392Ab2F2Oyw (ORCPT ); Fri, 29 Jun 2012 10:54:52 -0400 Message-ID: <1340981690.25226.3.camel@gurkel.linbit> Subject: [RFC] [TCP 1/3] tcp: Add MSG_NEW_PACKET flag to indicate preferable packet boundaries From: Andreas Gruenbacher To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Herbert Xu , "David S. Miller" Date: Fri, 29 Jun 2012 16:54:50 +0200 Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.3 (3.4.3-1.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The MSG_NEW_PACKET flag indicates to sendmsg / sendpage that the message or page should be put into a new packet even when there is still room left in the previous packet. In the tcp protocol, messages which are not sent immediately are queued. When more data is sent, it will be added to the last segment in that queue until that segment is "full" whenever possible; only then is a new segment added. Right now, there is no way to indicate when tcp should start a new segment. The new flag allows to control that. Signed-off-by: Andreas Gruenbacher --- include/linux/socket.h | 1 + net/ipv4/tcp.c | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/socket.h b/include/linux/socket.h index 25d6322..be166de 100644 --- a/include/linux/socket.h +++ b/include/linux/socket.h @@ -266,6 +266,7 @@ struct ucred { #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_NEW_PACKET 0x40000 /* tcp: try to put message into a new packet */ #define MSG_EOF MSG_FIN #define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exit for file diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 3ba605f..148aebe 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -854,7 +854,8 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse int size = min_t(size_t, psize, PAGE_SIZE - offset); bool can_coalesce; - if (!tcp_send_head(sk) || (copy = size_goal - skb->len) <= 0) { + if (!tcp_send_head(sk) || (copy = size_goal - skb->len) <= 0 || + (flags & MSG_NEW_PACKET)) { new_segment: if (!sk_stream_memory_free(sk)) goto wait_for_sndbuf; @@ -1044,7 +1045,7 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, copy = max - skb->len; } - if (copy <= 0) { + if (copy <= 0 || (flags & MSG_NEW_PACKET)) { new_segment: /* Allocate new segment. If the interface is SG, * allocate skb fitting to single page. -- 1.7.10.2