From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752763Ab0K0PAU (ORCPT ); Sat, 27 Nov 2010 10:00:20 -0500 Received: from mail.openrapids.net ([64.15.138.104]:41314 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752553Ab0K0PAR (ORCPT ); Sat, 27 Nov 2010 10:00:17 -0500 Date: Sat, 27 Nov 2010 10:00:15 -0500 From: Mathieu Desnoyers To: Christoph Lameter Cc: akpm@linux-foundation.org, Pekka Enberg , linux-kernel@vger.kernel.org, Eric Dumazet , Tejun Heo Subject: Re: [thisops uV2 04/10] x86: Support for this_cpu_add,sub,dec,inc_return Message-ID: <20101127150015.GE15365@Krystal> References: <20101126210937.383047168@linux.com> <20101126210951.303044608@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101126210951.303044608@linux.com> X-Editor: vi X-Info: http://www.efficios.com X-Operating-System: Linux/2.6.26-2-686 (i686) X-Uptime: 09:58:53 up 3 days, 20:01, 3 users, load average: 0.00, 0.00, 0.00 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Christoph Lameter (cl@linux.com) wrote: > Supply an implementation for x86 in order to generate more efficient code. > > Signed-off-by: Christoph Lameter > > --- > arch/x86/include/asm/percpu.h | 50 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 50 insertions(+) > > Index: linux-2.6/arch/x86/include/asm/percpu.h > =================================================================== > --- linux-2.6.orig/arch/x86/include/asm/percpu.h 2010-11-23 16:35:19.000000000 -0600 > +++ linux-2.6/arch/x86/include/asm/percpu.h 2010-11-23 16:36:05.000000000 -0600 > @@ -177,6 +177,45 @@ do { \ > } \ > } while (0) > > + > +/* > + * Add return operation > + */ > +#define percpu_add_return_op(var, val) \ > +({ \ > + typedef typeof(var) pao_T__; \ > + typeof(var) pfo_ret__ = val; \ > + if (0) { \ > + pao_T__ pao_tmp__; \ > + pao_tmp__ = (val); \ > + (void)pao_tmp__; \ > + } \ OK, I'm dumb: why is the above needed ? > + switch (sizeof(var)) { \ > + case 1: \ > + asm("xaddb %0, "__percpu_arg(1) \ > + : "+q" (pfo_ret__), "+m" (var) \ > + : : "memory"); \ > + break; \ > + case 2: \ > + asm("xaddw %0, "__percpu_arg(1) \ > + : "+r" (pfo_ret__), "+m" (var) \ > + : : "memory"); \ > + break; \ > + case 4: \ > + asm("xaddl %0, "__percpu_arg(1) \ > + : "+r"(pfo_ret__), "+m" (var) \ > + : : "memory"); \ > + break; \ > + case 8: \ > + asm("xaddq %0, "__percpu_arg(1) \ > + : "+re" (pfo_ret__), "+m" (var) \ > + : : "memory"); \ > + break; \ > + default: __bad_percpu_size(); \ > + } \ > + pfo_ret__ + (val); \ > +}) > + > #define percpu_from_op(op, var, constraint) \ > ({ \ > typeof(var) pfo_ret__; \ > @@ -300,6 +339,14 @@ do { \ > #define irqsafe_cpu_xor_2(pcp, val) percpu_to_op("xor", (pcp), val) > #define irqsafe_cpu_xor_4(pcp, val) percpu_to_op("xor", (pcp), val) (pcp) -> pcp. Same for other similar cases below. Thanks, Mathieu > > +#ifndef CONFIG_M386 > +#define __this_cpu_add_return_1(pcp, val) percpu_add_return_op((pcp), val) > +#define __this_cpu_add_return_2(pcp, val) percpu_add_return_op((pcp), val) > +#define __this_cpu_add_return_4(pcp, val) percpu_add_return_op((pcp), val) > +#define this_cpu_add_return_1(pcp, val) percpu_add_return_op((pcp), val) > +#define this_cpu_add_return_2(pcp, val) percpu_add_return_op((pcp), val) > +#define this_cpu_add_return_4(pcp, val) percpu_add_return_op((pcp), val) > +#endif > /* > * Per cpu atomic 64 bit operations are only available under 64 bit. > * 32 bit must fall back to generic operations. > @@ -324,6 +371,9 @@ do { \ > #define irqsafe_cpu_or_8(pcp, val) percpu_to_op("or", (pcp), val) > #define irqsafe_cpu_xor_8(pcp, val) percpu_to_op("xor", (pcp), val) > > +#define __this_cpu_add_return_8(pcp, val) percpu_add_return_op((pcp), val) > +#define this_cpu_add_return_8(pcp, val) percpu_add_return_op((pcp), val) > + > #endif > > /* This is not atomic against other CPUs -- CPU preemption needs to be off */ > -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com