Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756261AbZALVgJ (ORCPT ); Mon, 12 Jan 2009 16:36:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757595AbZALVfs (ORCPT ); Mon, 12 Jan 2009 16:35:48 -0500 Received: from mail-bw0-f21.google.com ([209.85.218.21]:64973 "EHLO mail-bw0-f21.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757454AbZALVfr (ORCPT ); Mon, 12 Jan 2009 16:35:47 -0500 Date: Mon, 12 Jan 2009 22:35:42 +0100 From: Frederik Deweerdt To: mingo@elte.hu Cc: andi@firstfloor.org, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: [patch] tlb flush_data: replace per_cpu with an array Message-ID: <20090112213539.GA10720@gambetta> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2624 Lines: 70 Hi, On x86_64 flush tlb data is stored in per_cpu variables. This is unnecessary because only the first NUM_INVALIDATE_TLB_VECTORS entries are accessed. This patch aims at making the code less confusing (there's nothing really "per_cpu") by using a plain array. It also would save some memory on most distros out there (Ubuntu x86_64 has NR_CPUS=64 by default). Regards, Frederik Signed-off-by: Frederik Deweerdt diff --git a/arch/x86/kernel/tlb_64.c b/arch/x86/kernel/tlb_64.c index f8be6f1..c177a1f 100644 --- a/arch/x86/kernel/tlb_64.c +++ b/arch/x86/kernel/tlb_64.c @@ -33,7 +33,7 @@ * To avoid global state use 8 different call vectors. * Each CPU uses a specific vector to trigger flushes on other * CPUs. Depending on the received vector the target CPUs look into - * the right per cpu variable for the flush data. + * the right array slot for the flush data. * * With more than 8 CPUs they are hashed to the 8 available * vectors. The limited global vector space forces us to this right now. @@ -54,7 +54,7 @@ union smp_flush_state { /* State is put into the per CPU data section, but padded to a full cache line because other CPUs can access it and we don't want false sharing in the per cpu data segment. */ -static DEFINE_PER_CPU(union smp_flush_state, flush_state); +static union smp_flush_state flush_state[NUM_INVALIDATE_TLB_VECTORS]; /* * We cannot call mmdrop() because we are in interrupt context, @@ -129,7 +129,7 @@ asmlinkage void smp_invalidate_interrupt(struct pt_regs *regs) * Use that to determine where the sender put the data. */ sender = ~regs->orig_ax - INVALIDATE_TLB_VECTOR_START; - f = &per_cpu(flush_state, sender); + f = &flush_state[sender]; if (!cpu_isset(cpu, f->flush_cpumask)) goto out; @@ -169,7 +169,7 @@ void native_flush_tlb_others(const cpumask_t *cpumaskp, struct mm_struct *mm, /* Caller has disabled preemption */ sender = smp_processor_id() % NUM_INVALIDATE_TLB_VECTORS; - f = &per_cpu(flush_state, sender); + f = &flush_state[sender]; /* * Could avoid this lock when @@ -205,8 +205,8 @@ static int __cpuinit init_smp_flush(void) { int i; - for_each_possible_cpu(i) - spin_lock_init(&per_cpu(flush_state, i).tlbstate_lock); + for (i = 0; i < ARRAY_SIZE(flush_state); i++) + spin_lock_init(&flush_state[i].tlbstate_lock); return 0; } -- 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/