Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756145Ab2EUINl (ORCPT ); Mon, 21 May 2012 04:13:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47257 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063Ab2EUINj (ORCPT ); Mon, 21 May 2012 04:13:39 -0400 Date: Mon, 21 May 2012 10:13:30 +0200 From: Alexander Gordeev To: Yinghai Lu Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Suresh Siddha , Cyrill Gorcunov Subject: Re: [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority delivery mode Message-ID: <20120521081330.GB28930@dhcp-26-207.brq.redhat.com> References: <20120518102640.GB31517@dhcp-26-207.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1949 Lines: 58 On Sat, May 19, 2012 at 01:53:36PM -0700, Yinghai Lu wrote: > > +static void > > +x2apic_cluster_vector_allocation_domain(int cpu, struct cpumask *retmask) > > +{ > > + ? ? ? cpumask_copy(retmask, cpu_possible_mask); > > why not using per_cpu(cpus_in_cluster, cpu) instead? Because it would lead to suboptimal results when updating IRQ affinity: int __ioapic_set_affinity(struct irq_data *data, const struct cpumask *mask, unsigned int *dest_id) { struct irq_cfg *cfg = data->chip_data; if (!cpumask_intersects(mask, cpu_online_mask)) return -1; if (assign_irq_vector(data->irq, data->chip_data, mask)) return -1; This call ^^^ will update cfg->domain with the value returned by the call to apic->vector_allocation_domain(). If per_cpu(cpus_in_cluster, cpu) is returned as cfg->domain here then all other clusters contained in the 'mask' will not be taken into consideration by the apic->cpu_mask_to_apicid_and() call below. cpumask_copy(data->affinity, mask); *dest_id = apic->cpu_mask_to_apicid_and(mask, cfg->domain); So we really need to submit all possible CPUs here ^^^ to be able finding the best/heaviest cluster out of the 'mask'. return 0; } > also you may add one per cpu var like x86_cpu_to_logical_cluster_apicid. Both cpu_mask_to_apicid() and cpu_mask_to_apicid_and() take a cpumask to derive the apicid from. Even though we could cache the value of apicid in 'x86_cpu_to_logical_cluster_apicid' variable, we still would have to unset CPUs which are not in the requested cpumask. That means scanning through the cpumask etc -- exactly what the the patch does now. Or I am missing your point here.. > Yinghai -- Regards, Alexander Gordeev agordeev@redhat.com -- 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/