Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755802AbZDKG01 (ORCPT ); Sat, 11 Apr 2009 02:26:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755345AbZDKG0N (ORCPT ); Sat, 11 Apr 2009 02:26:13 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53297 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755075AbZDKG0N (ORCPT ); Sat, 11 Apr 2009 02:26:13 -0400 Message-Id: <200904110617.n3B6HJ7W026502@imap1.linux-foundation.org> Subject: [patch for 2.6.30 2/2] arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU interrupts To: lenb@kernel.org Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, davej@redhat.com, efault@gmx.de, len.brown@intel.com, mingo@elte.hu, rusty@rustcorp.com.au, tglx@linutronix.de, venkatesh.pallipadi@intel.com, yakui.zhao@intel.com, yanmin_zhang@linux.intel.com From: akpm@linux-foundation.org Date: Fri, 10 Apr 2009 23:17:18 -0700 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2050 Lines: 56 From: Andrew Morton In drv_read(), check to see whether we can run the rdmsr() on the current CPU. If so, do that. So smp_call_function_single() can avoid the IPI. Arguably, cpumask_any() should do this. Cc: Rusty Russell Cc: Ingo Molnar Cc: Venkatesh Pallipadi Cc: Len Brown Cc: Zhao Yakui Cc: Dave Jones Cc: Thomas Gleixner Tested-by: Mike Galbraith Cc: "Zhang, Yanmin" Signed-off-by: Andrew Morton --- arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff -puN arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts +++ a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c @@ -197,9 +197,22 @@ static void do_drv_write(void *_cmd) static void drv_read(struct drv_cmd *cmd) { - cmd->val = 0; + int target_cpu; /* The CPU on which to perform thr rdmsr() */ + int this_cpu; + + /* + * If the current CPU is in cmd->mask then run the rdmsr() on this + * CPU to avoid the cross-cpu interrupt. + */ + this_cpu = get_cpu(); + if (cpu_isset(this_cpu, *(cmd->mask))) + target_cpu = this_cpu; + else + target_cpu = cpumask_any(cmd->mask); - smp_call_function_single(cpumask_any(cmd->mask), do_drv_read, cmd, 1); + cmd->val = 0; + smp_call_function_single(target_cpu, do_drv_read, cmd, 1); + put_cpu(); } static void drv_write(struct drv_cmd *cmd) _ -- 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/