Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752536AbYLAGum (ORCPT ); Mon, 1 Dec 2008 01:50:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750740AbYLAGue (ORCPT ); Mon, 1 Dec 2008 01:50:34 -0500 Received: from e28smtp02.in.ibm.com ([59.145.155.2]:50317 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750709AbYLAGue (ORCPT ); Mon, 1 Dec 2008 01:50:34 -0500 Message-ID: <49338933.1030401@linux.vnet.ibm.com> Date: Mon, 01 Dec 2008 12:20:27 +0530 From: Mahesh Jagannath Salgaonkar User-Agent: Thunderbird 2.0.0.18 (X11/20081119) MIME-Version: 1.0 To: Ingo Molnar CC: Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Peter Zijlstra , svaidy@linux.vnet.ibm.com Subject: Re: [PATCH] Don't export sched_mc_power_savings in laptops References: <1227957612-7000-1-git-send-email-mahesh@linux.vnet.ibm.com> <20081130174034.GA28614@elte.hu> In-Reply-To: <20081130174034.GA28614@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1683 Lines: 49 Ingo Molnar wrote: > * Mahesh Salgaonkar wrote: > > >> Fix to prevent sched_mc_power_saving from being exported through sysfs >> for multicore single socket (Laptop). >> >> CPU core map of the boot cpu should be equal to possible number >> of cpus for single socket system. >> >> This fix has been developed at FOSS.in kernel workout. >> >> Signed-off-by: Mahesh Salgaonkar >> >> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h >> index 4850e4b..4adc830 100644 >> --- a/arch/x86/include/asm/topology.h >> +++ b/arch/x86/include/asm/topology.h >> @@ -239,7 +239,7 @@ struct pci_bus; >> void set_pci_bus_resources_arch_default(struct pci_bus *b); >> >> #ifdef CONFIG_SMP >> -#define mc_capable() (boot_cpu_data.x86_max_cores > 1) >> +#define mc_capable() (cpus_weight(per_cpu(cpu_core_map,0)) != nr_cpu_ids) >> > > hm, dunno. sched_mc_power_savings should have no effect on single-socket > systems, right? So the knob should have no effect. > > Ingo > Hi Ingo, Yes, it will not have any effect but it enables additional code path leading to an overhead in case of single-socket system. This overhead is only if "sched_mc_power_savings = 1", however we are still leaving it to zero (default) and preventing user space from turning it on by mistake. Thanks, -Mahesh. -- 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/