From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263764AbTJOSRh (ORCPT ); Wed, 15 Oct 2003 14:17:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263864AbTJOSRh (ORCPT ); Wed, 15 Oct 2003 14:17:37 -0400 Received: from zcars04e.nortelnetworks.com ([47.129.242.56]:53413 "EHLO zcars04e.nortelnetworks.com") by vger.kernel.org with ESMTP id S263764AbTJOSRe (ORCPT ); Wed, 15 Oct 2003 14:17:34 -0400 Message-ID: <3F8D8F3A.5040506@nortelnetworks.com> Date: Wed, 15 Oct 2003 14:17:30 -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> 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 Tue, 14 Oct 2003, Chris Friesen wrote: >>I have a long-running cpu hog background task, and a high-priority >>critical task that waits on a socket for network traffic. When a packet >>comes in, I'd like the cpu hog to be swapped out ASAP, rather than >>waiting for the end of the timeslice. Is there any way to make this happen? > What do you mean for high priority? Is it an RT task? The wakeup (AKA > inserion in the run queue) happen soon : > IRQ->do_IRQ->softirq->net_rx_action->ip_rcv->... > but if your task is not RT there no guarantee that it'll preempt the > current running. Yes, it was an RT task. 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. 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