From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com ([134.134.136.24]:65089 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754720AbcFPPPc (ORCPT ); Thu, 16 Jun 2016 11:15:32 -0400 Date: Thu, 16 Jun 2016 11:19:51 -0400 From: Keith Busch To: Bart Van Assche Cc: Christoph Hellwig , "tglx@linutronix.de" , "axboe@fb.com" , "linux-block@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 02/13] irq: Introduce IRQD_AFFINITY_MANAGED flag Message-ID: <20160616151950.GA11840@localhost.localdomain> References: <0412b942-ea0d-d4eb-c724-8243d12ff6f3@sandisk.com> <20160615102311.GA16619@lst.de> <67ef7a1c-56e1-db2c-b038-f9784fc1f52f@sandisk.com> <20160615151415.GA1919@localhost.localdomain> <7f0b16bd-b39f-99e6-c1c1-6a508bf9bbbf@sandisk.com> <20160615160316.GB1919@localhost.localdomain> <86aa652b-48d0-a7bb-683e-bf43939aa811@sandisk.com> <20160615200655.GB7637@localhost.localdomain> <20160615201213.GC7637@localhost.localdomain> <7a61fe73-2808-70b4-e3b2-b6a924559d9d@sandisk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <7a61fe73-2808-70b4-e3b2-b6a924559d9d@sandisk.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, Jun 15, 2016 at 10:50:53PM +0200, Bart Van Assche wrote: > Does it matter on x86 systems whether or not these interrupt vectors are > also associated with a CPU with a higher CPU number? Although multiple bits > can be set in /proc/irq//smp_affinity only the first bit counts on x86 > platforms. In default_cpu_mask_to_apicid_and() it is easy to see that only > the first bit that has been set in that mask counts on x86 systems. Wow, thanks for the information. I didn't know the apic wasn't using the full cpu mask, so this changes how I need to look at this, and will experiment with such a configuration.