Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757458Ab2FTRX5 (ORCPT ); Wed, 20 Jun 2012 13:23:57 -0400 Received: from terminus.zytor.com ([198.137.202.10]:39475 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752404Ab2FTRX4 (ORCPT ); Wed, 20 Jun 2012 13:23:56 -0400 Message-ID: <4FE2071B.5040602@zytor.com> Date: Wed, 20 Jun 2012 10:23:39 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: mingo@kernel.org, hpa@zytor.com, agordeev@redhat.com, linux-kernel@vger.kernel.org, yinghai@kernel.org, suresh.b.siddha@intel.com, tglx@linutronix.de CC: linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/apic] x86/apic: Try to spread IRQ vectors to different priority levels References: <20120607131514.GD4759@dhcp-26-207.brq.redhat.com> In-Reply-To: X-Enigmail-Version: 1.4.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1421 Lines: 35 On 06/08/2012 07:50 AM, tip-bot for Alexander Gordeev wrote: > Commit-ID: 1bccd58bfffc5a677051937b332b71f0686187c1 > Gitweb: http://git.kernel.org/tip/1bccd58bfffc5a677051937b332b71f0686187c1 > Author: Alexander Gordeev > AuthorDate: Thu, 7 Jun 2012 15:15:15 +0200 > Committer: Ingo Molnar > CommitDate: Fri, 8 Jun 2012 11:44:28 +0200 > > x86/apic: Try to spread IRQ vectors to different priority levels > > When assigning a new vector it is primarially done by adding 8 > to the previously given out vector number. Hence, two > consequently allocated vector numbers would likely fall into the > same priority level. Try to spread vector numbers to different > priority levels better by changing the step from 8 to 16. > OK, stupid question: WHY? In general, in Linux the random prioritization is actually a negative. The only reason for the spreading by 8 is because of bugs/misfeatures in old APIC implementations which made them handle more than two interrupts per priority level rather inefficiently. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/