From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030211AbWGFGlT (ORCPT ); Thu, 6 Jul 2006 02:41:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030224AbWGFGlT (ORCPT ); Thu, 6 Jul 2006 02:41:19 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:40877 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1030211AbWGFGlS (ORCPT ); Thu, 6 Jul 2006 02:41:18 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Andrew Morton Cc: kmannth@gmail.com, linux-kernel@vger.kernel.org, mingo@elte.hu, tglx@linutronix.de, Natalie.Protasevich@UNISYS.com Subject: Re: 2.6.17-mm6 References: <20060703030355.420c7155.akpm@osdl.org> <20060705155037.7228aa48.akpm@osdl.org> <20060705164457.60e6dbc2.akpm@osdl.org> <20060705164820.379a69ba.akpm@osdl.org> <20060705172545.815872b6.akpm@osdl.org> <20060705225905.53e61ca0.akpm@osdl.org> Date: Thu, 06 Jul 2006 00:40:31 -0600 In-Reply-To: <20060705225905.53e61ca0.akpm@osdl.org> (Andrew Morton's message of "Wed, 5 Jul 2006 22:59:05 -0700") Message-ID: User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton writes: > On Wed, 05 Jul 2006 23:42:00 -0600 > ebiederm@xmission.com (Eric W. Biederman) wrote: > >> So I suspect that we need to de-percpuify kernel_stat.irqs. > > I think so. We do: > > struct irq_desc *desc = irq_desc + irq; > > kstat_this_cpu.irqs[irq]++; > > followed immediately by > > spin_lock(&desc->lock); > > false optimisation, or what? As an optimization I can't think of a reason. It is kind of interesting to report that information by cpu. in /proc/interrupts (see show_interrupts). But except for understanding system behavior I can't think of a reason for reporting that information. It was useful information to have when debugging the irq migration code. Eric