Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 3 Oct 2001 12:54:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 3 Oct 2001 12:54:07 -0400 Received: from chiara.elte.hu ([157.181.150.200]:54280 "HELO chiara.elte.hu") by vger.kernel.org with SMTP id ; Wed, 3 Oct 2001 12:53:51 -0400 Date: Wed, 3 Oct 2001 18:51:55 +0200 (CEST) From: Ingo Molnar Reply-To: To: jamal Cc: , Alexey Kuznetsov , Robert Olsson , Benjamin LaHaise , , Linus Torvalds , Alan Cox Subject: Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5 In-Reply-To: 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 Wed, 3 Oct 2001, jamal wrote: > this code was added by Robert to check something; cant remember the > details on that specific date. [...] ok. > > + while (!list_empty(&queue->poll_list)) { > > + struct net_device *dev; > > [...] > > + if (dev->quota <= 0 || dev->poll(dev, &budget)) { > > + local_irq_disable(); > > + list_del(&dev->poll_list); > > + list_add_tail(&dev->poll_list, &queue->poll_list); > You misunderstood. This is to enforce fairness. [...] (i did not criticize the list_add/list_del in any way, it's obviously correct to cycle the polled devices. I highlited that code only to show that the current patch as-is polls too agressively for generic server load.) > Read the paper. (i prefer source code. Can i assume the 'authorative' patch to be the one with the "goto not_done;" line removed, correct?) > > In a generic computing environment i want to spend cycles doing useful > > work, not polling. Even the quick kpolld hack [which i dropped, so please > > dont regard it as a 'competitor' patch] i consider superior to this, as i > > can renice kpolld to reduce polling. (plus kpolld sucks up available idle > > cycles as well.) Unless i royally misunderstand it, i cannot stop the > > above code from wasting my cycles, and if that is true i do not want to > > see it in the kernel proper in this form. > The interupt just flags "i, netdev, have work to do"; [...] (and the only thing i pointed out was that the patch as-is did not limit the amount of polling done.) > > *if* you can make polling a success in ~90% of the time we enter > > tulip_poll() under non-specific server load (ie. not routing), then i > > think you have really good metrics. > > we can make it 100% successful; i mentioned that we only do work, if > there is work to be done. can you really make it 100% successful for rx? Ie. do you only ever call the ->poll() function if there is a new packet waiting? How do you know with a 100% probability that someone on the network just sent a new packet waiting? (without receiving an interrupt to begin with that is.) Ingo - 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/