From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: [PATCH net-next] tcp: double default TSQ output bytes limit Date: Wed, 3 Jun 2015 11:10:42 +0100 Message-ID: <1433326242-4061-1-git-send-email-wei.liu2@citrix.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Stefano Stabellini , George Dunlap , Wei Liu , David Miller , Eric Dumazet To: Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:56508 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751169AbbFCKQ6 (ORCPT ); Wed, 3 Jun 2015 06:16:58 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Xen virtual network driver has higher latency than a physical NIC. Having only 128K as limit for TSQ introduced 30% regression in guest throughput. This patch raises the limit to 256K. This reduces the regression to 8%. This buys us more time to work out a proper solution in the long run. Signed-off-by: Wei Liu Cc: David Miller Cc: Eric Dumazet --- net/ipv4/tcp_output.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 190538a..eeb59be 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -50,8 +50,8 @@ int sysctl_tcp_retrans_collapse __read_mostly = 1; */ int sysctl_tcp_workaround_signed_windows __read_mostly = 0; -/* Default TSQ limit of two TSO segments */ -int sysctl_tcp_limit_output_bytes __read_mostly = 131072; +/* Default TSQ limit of four TSO segments */ +int sysctl_tcp_limit_output_bytes __read_mostly = 262144; /* This limits the percentage of the congestion window which we * will allow a single TSO frame to consume. Building TSO frames -- 1.9.1