From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Chapman Subject: Re: RFC: possible NAPI improvements to reduce interrupt rates for low traffic rates Date: Thu, 06 Sep 2007 16:30:30 +0100 Message-ID: <46E01D16.5000609@katalix.com> References: <200709061416.l86EG0Vb017675@quickie.katalix.com> <20070906153700.57a0c448@oldman> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, hadi@cyberus.ca, davem@davemloft.net, jeff@garzik.org, mandeep.baines@gmail.com, ossthema@de.ibm.com To: Stephen Hemminger Return-path: Received: from s36.avahost.net ([74.53.95.194]:43132 "EHLO s36.avahost.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755421AbXIFPae (ORCPT ); Thu, 6 Sep 2007 11:30:34 -0400 In-Reply-To: <20070906153700.57a0c448@oldman> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Stephen Hemminger wrote: > What about the latency that NAPI imposes? Right now there are certain applications that > don't like NAPI because it add several more microseconds, and this may make it worse. Latency is something that I think this approach will actually improve, at the expense of additional polling. Or is it the ksoftirqd scheduling latency that you are referring to? > Maybe a per-device flag or tuning parameters (like weight sysfs value)? or some other > way to set low-latency values. Yes. I'd like to think good defaults could be derived though, perhaps based on settings like CONFIG_PREEMPT, CONFIG_HIGH_RES_TIMER, CONFIG_HZ and maybe even bogomips / nr_cpus. -- James Chapman Katalix Systems Ltd http://www.katalix.com Catalysts for your Embedded Linux software development