From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759961Ab2EVRWv (ORCPT ); Tue, 22 May 2012 13:22:51 -0400 Received: from mga14.intel.com ([143.182.124.37]:45632 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751747Ab2EVRWt (ORCPT ); Tue, 22 May 2012 13:22:49 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="102949844" Subject: Re: [PATCH 2/2] x2apic, cluster: use all the members of one cluster specified in the smp_affinity mask for the interrupt desintation From: Suresh Siddha Reply-To: Suresh Siddha To: Ingo Molnar Cc: agordeev@redhat.com, yinghai@kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, gorcunov@openvz.org Date: Tue, 22 May 2012 10:21:15 -0700 In-Reply-To: <20120522070428.GA15738@gmail.com> References: <1337643880.1997.166.camel@sbsiddha-desk.sc.intel.com> <1337644682-19854-1-git-send-email-suresh.b.siddha@intel.com> <1337644682-19854-2-git-send-email-suresh.b.siddha@intel.com> <20120522070428.GA15738@gmail.com> Organization: Intel Corp Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.0.3 (3.0.3-1.fc15) Content-Transfer-Encoding: 7bit Message-ID: <1337707275.1997.184.camel@sbsiddha-desk.sc.intel.com> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-05-22 at 09:04 +0200, Ingo Molnar wrote: > * Suresh Siddha wrote: > > > If the HW implements round-robin interrupt delivery, this > > enables multiple cpu's (which are part of the user specified > > interrupt smp_affinity mask and belong to the same x2apic > > cluster) to service the interrupt. > > Could/should we do something similar for regular APICs as well? > They too support masks and LowestPrio delivery - and doing that > will increase test coverage rather significantly. Existing logical flat xapic mode already takes advantage of this today. And that apic driver allows multiple cpu's to be set in the destination field allowing round-robin/power-aware interrupt delivery etc depending on the platform capabilities etc. So most of the laptops with 8 or less logical cpu's should take advantage of this today. For bigger platforms, we use physical xapic mode. Some older kernels used xapic cluster mode, which allows 4 members in a cluster. With two HT siblings, that will leave room for only 2 cores. So the benefit will be limited. And on the multi-socket platforms, x2apic/vt-d will be available and used for various other reasons too (virtualization etc). x2apic is available on desktop/laptop models too. So for legacy xapic, we can use logical flat mode to take advantage of these HW modes. thanks, suresh