From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: Re: performance regression on HiperSockets depending on MTU size Date: Tue, 27 Nov 2012 06:21:42 +0000 (UTC) Message-ID: References: <20121126153242.GA61652@tuxmaker.boeblingen.de.ibm.com> <1353946351.30446.1779.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from plane.gmane.org ([80.91.229.3]:42612 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755918Ab2K0GV5 (ORCPT ); Tue, 27 Nov 2012 01:21:57 -0500 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1TdEYW-0007OI-7i for netdev@vger.kernel.org; Tue, 27 Nov 2012 07:22:04 +0100 Received: from 112.132.205.99 ([112.132.205.99]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 27 Nov 2012 07:22:04 +0100 Received: from xiyou.wangcong by 112.132.205.99 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 27 Nov 2012 07:22:04 +0100 Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 26 Nov 2012 at 16:12 GMT, Eric Dumazet wrote: > Hi Frank, thanks for this report. > > You could tweak tcp_limit_output_bytes, but IMO the root of the problem > is in the driver itself. > > For example, I had to change mlx4 driver for the same problem : Make > sure a TX packet can be "TX completed" in a short amount of time. > > In the case of mlx4, the wait time was 128 us, but I suspect on your > case its more like an infinite time or several ms. > > The driver is delaying the free of TX skb by a fixed amount of time, > or relies on following transmits to perform the TX completion > Eric, Do you have a full list of such commits? I am trying to backport TSQ to 2.6.32, and of course I don't want to miss these commits either. Thanks!