From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752149AbXLEX1Y (ORCPT ); Wed, 5 Dec 2007 18:27:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751063AbXLEX1Q (ORCPT ); Wed, 5 Dec 2007 18:27:16 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:42382 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750954AbXLEX1P (ORCPT ); Wed, 5 Dec 2007 18:27:15 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: "Natalie Protasevich" Cc: "Len Brown" , "Andi Kleen" , "Ingo Molnar" , "Thomas Gleixner" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] i386 IOAPIC: de-fang IRQ compression References: <200711280121.18376.lenb@kernel.org> <32209efe0712050525j486922a9s471f3871e69aedff@mail.gmail.com> Date: Wed, 05 Dec 2007 16:25:11 -0700 In-Reply-To: <32209efe0712050525j486922a9s471f3871e69aedff@mail.gmail.com> (Natalie Protasevich's message of "Wed, 5 Dec 2007 05:25:54 -0800") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Natalie Protasevich" writes: > On Nov 27, 2007 10:21 PM, Len Brown wrote: >> commit c434b7a6aedfe428ad17cd61b21b125a7b7a29ce >> (x86: avoid wasting IRQs for PCI devices) >> created a concept of "IRQ compression" on i386 >> to conserve IRQ numbers on systems with many >> sparsely populated IO APICs. >> >> The same scheme was also added to x86_64, >> but later removed when x86_64 recieved an IRQ over-haul >> that made it unnecessary -- including per-CPU >> IRQ vectors that greatly increased the IRQ capacity >> on the machine. >> >> i386 has not received the analogous over-haul, >> and thus a previous attempt to delete IRQ compression >> from i386 was rejected on the theory that there may >> exist machines that actually need it. The fact is >> that the author of IRQ compression patch was unable >> to confirm the actual existence of such a system. > > Those systems did exist (and still exist actually). They used over 200 > irqs sometimes and with "normal" IRQ allocation they were failing even > before reaching half of their I/O configuration. So simple removal > wouldn't work for those, dynamic allocation sure would. They "scrolled > off the topic" though because new generations of such machines are not > 32 bit anymore. So the author didn't actually object :) it was the > other users of large 32 bit platforms that did. Natalie. Did they just have over 200 irqs/gsis or did they actually use over 200 irqs? In particular is a large NR_IRQS plus dynamic vector allocation sufficient for all cases you know about? Eric