From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Leon Woestenberg" Subject: Re: [Ksummit-2008-discuss] Delayed interrupt work, thread pools Date: Wed, 2 Jul 2008 13:19:39 +0200 Message-ID: References: <1214916335.20711.141.camel@pasglop> <486B0298.5030508@linux.intel.com> <1214977447.21182.33.camel@pasglop> <87zlp0sg4l.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: benh@kernel.crashing.org, "Arjan van de Ven" , ksummit-2008-discuss@lists.linux-foundation.org, "Linux Kernel list" , "Jeremy Kerr" , RT To: "Andi Kleen" Return-path: Received: from an-out-0708.google.com ([209.85.132.250]:58879 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758953AbYGBLTk (ORCPT ); Wed, 2 Jul 2008 07:19:40 -0400 Received: by an-out-0708.google.com with SMTP id d40so60768and.103 for ; Wed, 02 Jul 2008 04:19:39 -0700 (PDT) In-Reply-To: <87zlp0sg4l.fsf@basil.nowhere.org> Content-Disposition: inline Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hello, (including linux-rt-users in the CC:, irqthreads are on-topic there) On Wed, Jul 2, 2008 at 1:02 PM, Andi Kleen wrote: > Benjamin Herrenschmidt writes: > >>> how much of this would be obsoleted if we had irqthreads ? >> >> I'm not sure irqthreads is what I want... >> > I also think interrupts threads are a bad idea in many cases because > their whole "advantage" over classical interrupts is that they can > block. Now blocking can be usually take a unbounded potentially long > time. > > What do you do when there are more interrupts in that unbounded time? > If by irqthreads the -rt implementation is meant, isn't this what happens: irq kernel handler masks the source interrupt irq handler awakes the matching irqthread (they always are present) irqthread is scheduled, does work and returns irq kernel unmasks the source interrupt > Create more interrupt threads? At some point you'll have hundreds > of threads doing nothing when you're unlucky. > Each irqthread handles one irq. So now new irq thread would spawn for any interrupt. Regards, -- Leon