Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 8 Oct 2001 10:05:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 8 Oct 2001 10:05:07 -0400 Received: from [216.191.240.114] ([216.191.240.114]:27525 "EHLO shell.cyberus.ca") by vger.kernel.org with ESMTP id ; Mon, 8 Oct 2001 10:04:50 -0400 Date: Mon, 8 Oct 2001 09:58:22 -0400 (EDT) From: jamal To: cc: Andreas Dilger , , , , , , , Subject: Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5 In-Reply-To: <200110051917.XAA23007@ms2.inr.ac.ru> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 5 Oct 2001 kuznet@ms2.inr.ac.ru wrote: > Hello! > > > One question which I have is why would you ever want to continue polling > > if there is no work to be done? Is it a tradeoff between the amount of > > time to handle an IRQ vs. the time to do a poll? > > Yes. IRQ even taken alone eat non-trivial amount of resources. > > Actually, I remember Jamal worked with machine, which had > no io-apic and only irq ack/mask/unmask eated >15% of cpu there. :-) > This was Robert actually; conclusion was Interupts are very expensive. If we can get rid of as many of them as possible, we are getting a side benefit. I cant find the old data, but Robert has some data over here: http://robur.slu.se/Linux/net-development/experiments/010301 > "some hysteresis" is right word. This loop is an experiment with still > unknown result yet. Originally, Jamal proposed to spin several times. > I killed this. It was a good idea you killed it, now that i think in retrospect, The solution is much cleaner without it. > Robert proposed to check inifinite loop yet. (Note, > jiffies check is just a way to get rid of completely idle devices, > one jiffie is enough lonf time to be considered infinite). > In my opinion we really dont need this. I did some quick testing, with and without it and i dont see any differences. cheers, jamal - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/