From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965089Ab2JAXX4 (ORCPT ); Mon, 1 Oct 2012 19:23:56 -0400 Received: from 1wt.eu ([62.212.114.60]:35342 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932873Ab2JAXBU (ORCPT ); Mon, 1 Oct 2012 19:01:20 -0400 Message-Id: <20121001225203.596263689@1wt.eu> User-Agent: quilt/0.48-1 Date: Tue, 02 Oct 2012 00:54:18 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Willy Tarreau , Eric Dumazet , Greg Kroah-Hartman Subject: [ 141/180] tcp: do_tcp_sendpages() must try to push data out on oom conditions In-Reply-To: <6a854f579a99b4fe2efaca1057e8ae22@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Willy Tarreau commit bad115cfe5b509043b684d3a007ab54b80090aa1 upstream. Since recent changes on TCP splicing (starting with commits 2f533844 "tcp: allow splice() to build full TSO packets" and 35f9c09f "tcp: tcp_sendpages() should call tcp_push() once"), I started seeing massive stalls when forwarding traffic between two sockets using splice() when pipe buffers were larger than socket buffers. Latest changes (net: netdev_alloc_skb() use build_skb()) made the problem even more apparent. The reason seems to be that if do_tcp_sendpages() fails on out of memory condition without being able to send at least one byte, tcp_push() is not called and the buffers cannot be flushed. After applying the attached patch, I cannot reproduce the stalls at all and the data rate it perfectly stable and steady under any condition which previously caused the problem to be permanent. The issue seems to have been there since before the kernel migrated to git, which makes me think that the stalls I occasionally experienced with tux during stress-tests years ago were probably related to the same issue. This issue was first encountered on 3.0.31 and 3.2.17, so please backport to -stable. Signed-off-by: Willy Tarreau Acked-by: Eric Dumazet Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index f095659..b9644d8 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -838,8 +838,7 @@ new_segment: wait_for_sndbuf: set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); wait_for_memory: - if (copied) - tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH); + tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH); if ((err = sk_stream_wait_memory(sk, &timeo)) != 0) goto do_error; -- 1.7.2.1.45.g54fbc