From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264285AbTJOUNg (ORCPT ); Wed, 15 Oct 2003 16:13:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264286AbTJOUNg (ORCPT ); Wed, 15 Oct 2003 16:13:36 -0400 Received: from zcars04f.nortelnetworks.com ([47.129.242.57]:9140 "EHLO zcars04f.nortelnetworks.com") by vger.kernel.org with ESMTP id S264285AbTJOUNf (ORCPT ); Wed, 15 Oct 2003 16:13:35 -0400 Message-ID: <3F8DAA6B.7060609@nortelnetworks.com> Date: Wed, 15 Oct 2003 16:13:31 -0400 X-Sybari-Space: 00000000 00000000 00000000 00000000 From: Chris Friesen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.8) Gecko/20020204 X-Accept-Language: en-us MIME-Version: 1.0 To: Davide Libenzi Cc: Linux Kernel Subject: Re: question on incoming packets and scheduler References: <3F8CA55C.1080203@nortelnetworks.com> <3F8D8F3A.5040506@nortelnetworks.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Davide Libenzi wrote: > On Wed, 15 Oct 2003, Chris Friesen wrote: >>It appears that 2.4.20 fixes this issue, but there is another one >>remaining that the latency appears to be dependent on the number of >>incoming packets. See thread "incoming packet latency in 2.4.[18-20]" >>for details. This behaviour doesn't show up in 2.6, and I'm about to >>test 2.4.22. > Are you sure it's not a livelock issue during the burst? I dunno, you tell me. The test app simply sits in select() until a packet comes in, then it spins on recvmsg() until there are no more messages. It uses SO_TIMESTAMP to find out when the packet got to the kernel, and does a gettimeofday() right after the recvmsg(), then calculates the delta for each packet and the overall average. With 2.4.[18-20], the overall average goes up when the number of packets goes up. For 2.6.0-test6, it stays constant. Chris -- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com