From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261728AbUB0HO4 (ORCPT ); Fri, 27 Feb 2004 02:14:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261735AbUB0HO4 (ORCPT ); Fri, 27 Feb 2004 02:14:56 -0500 Received: from mx1.redhat.com ([66.187.233.31]:59365 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S261728AbUB0HOt (ORCPT ); Fri, 27 Feb 2004 02:14:49 -0500 Date: Fri, 27 Feb 2004 08:14:45 +0100 From: Arjan van de Ven To: Mark Gross Cc: Tim Bird , root@chaos.analogic.com, linux kernel Subject: Re: Why no interrupt priorities? Message-ID: <20040227071445.GA5695@devserv.devel.redhat.com> References: <403E4363.2070908@am.sony.com> <403E5EF7.7080309@am.sony.com> <1077831001.4443.9.camel@laptop.fenrus.com> <200402261421.34885.mgross@linux.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="tThc/1wpZn/ma/RB" Content-Disposition: inline In-Reply-To: <200402261421.34885.mgross@linux.intel.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --tThc/1wpZn/ma/RB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Feb 26, 2004 at 02:21:34PM -0800, Mark Gross wrote: > > hardware IRQ priorities are useless for the linux model. In linux, the > > hardirq runs *very* briefly and then lets the softirq context do the > > longer taking work. hardware irq priorities then don't matter really > > because the hardirq's are hardly ever interrupted really, and when they > > are they cause a performance *loss* due to cache trashing. The latency > > added by waiting briefly is going to be really really short for any sane > > hardware. > > Keep in mind the context is Linux running on non-sane hardware, sloooow CPUs, 50Mhz is already really really fast in this context. > latency sensitive small io buffers etc. Losing system wide throughput to have > the hardware codec not be starved is a happy trade off to make. The point I tried to make was that it would INCREASE latency. Unless you have misdesigned device drivers, which is something that is fixable :) --tThc/1wpZn/ma/RB Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFAPu5kxULwo51rQBIRAueRAJ9/9fVkGjp3/kov2GDeJpWoMhkkwQCeMSvh 4YEN64kc5xUfFmcyOJhQwLY= =qaEk -----END PGP SIGNATURE----- --tThc/1wpZn/ma/RB--