From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752794AbZHCFMn (ORCPT ); Mon, 3 Aug 2009 01:12:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751738AbZHCFMn (ORCPT ); Mon, 3 Aug 2009 01:12:43 -0400 Received: from hera.kernel.org ([140.211.167.34]:57296 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751355AbZHCFMm (ORCPT ); Mon, 3 Aug 2009 01:12:42 -0400 Message-ID: <4A7671B3.1050208@kernel.org> Date: Mon, 03 Aug 2009 14:12:19 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.22 (X11/20090605) MIME-Version: 1.0 To: Linus Torvalds CC: Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List Subject: [PATCH 3/3] x86: collect hot percpu variables into one cacheline References: <200907311813.n6VIDe9S023442@voreg.hos.anvin.org> <20090731195705.GA12270@elte.hu> <4A76421E.3040005@kernel.org> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Mon, 03 Aug 2009 05:12:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On x86_64, percpu variables current_task and kernel_stack are used for get_current() and current_thread_info() respectively and thus are often used close to each other. Move definition of current_task to kernel/cpu/common.c right above kernel_stack definition and align it to cacheline so that they always fall into the same cacheline. Two percpu variables defined there together - irq_stack_ptr and irq_count - are also pretty hot and will benefit from sharing the cacheline. For consistency, current_task definition for x86_32 is also moved to kernel/cpu/common.c. Putting current_task and kernel_stack into the same cacheline was suggested by Linus Tolvards. Signed-off-by: Tejun Heo Cc: Linus Tolvards Cc: Ingo Molnar --- For now this should do but adding DEFINE_PER_CPU_HOT() definitely is a viable option. arch/x86/kernel/cpu/common.c | 15 +++++++++++++-- arch/x86/kernel/process_32.c | 3 --- arch/x86/kernel/process_64.c | 3 --- 3 files changed, 13 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 12493c5..1bd88ed 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -987,13 +987,21 @@ struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table }; DEFINE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __aligned(PAGE_SIZE); -DEFINE_PER_CPU(char *, irq_stack_ptr) = - init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64; +/* + * The following four percpu variables are hot. Align current_task to + * cacheline size such that all four fall in the same cacheline. + */ +DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned = + &init_task; +EXPORT_PER_CPU_SYMBOL(current_task); DEFINE_PER_CPU(unsigned long, kernel_stack) = (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE; EXPORT_PER_CPU_SYMBOL(kernel_stack); +DEFINE_PER_CPU(char *, irq_stack_ptr) = + init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64; + DEFINE_PER_CPU(unsigned int, irq_count) = -1; /* @@ -1041,6 +1049,9 @@ DEFINE_PER_CPU(struct orig_ist, orig_ist); #else /* CONFIG_X86_64 */ +DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task; +EXPORT_PER_CPU_SYMBOL(current_task); + #ifdef CONFIG_CC_STACKPROTECTOR DEFINE_PER_CPU(unsigned long, stack_canary); #endif diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 59f4524..daa4107 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -61,9 +61,6 @@ asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); -DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task; -EXPORT_PER_CPU_SYMBOL(current_task); - /* * Return saved PC of a blocked thread. */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index ebefb54..c4c675d 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -55,9 +55,6 @@ asmlinkage extern void ret_from_fork(void); -DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task; -EXPORT_PER_CPU_SYMBOL(current_task); - DEFINE_PER_CPU(unsigned long, old_rsp); static DEFINE_PER_CPU(unsigned char, is_idle); -- 1.6.0.2