From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 7A71E6B004A for ; Tue, 30 Nov 2010 14:13:39 -0500 (EST) Received: by wwi18 with SMTP id 18so38403wwi.2 for ; Tue, 30 Nov 2010 11:13:32 -0800 (PST) Subject: Re: [thisops uV3 07/18] highmem: Use this_cpu_xx_return() operations From: Eric Dumazet In-Reply-To: <20101130190845.216537525@linux.com> References: <20101130190707.457099608@linux.com> <20101130190845.216537525@linux.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 30 Nov 2010 20:13:28 +0100 Message-ID: <1291144408.2904.232.camel@edumazet-laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: akpm@linux-foundation.org, Pekka Enberg , Peter Zijlstra , Catalin Marinas , linux-kernel@vger.kernel.org, Mathieu Desnoyers , Tejun Heo , linux-mm@kvack.org List-ID: Le mardi 30 novembre 2010 A 13:07 -0600, Christoph Lameter a A(C)crit : > piA?ce jointe document texte brut (this_cpu_highmem) > Use this_cpu operations to optimize access primitives for highmem. > > The main effect is the avoidance of address calculations through the > use of a segment prefix. > > Cc: Peter Zijlstra > Cc: Catalin Marinas > Signed-off-by: Christoph Lameter > > --- > include/linux/highmem.h | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > Index: linux-2.6/include/linux/highmem.h > =================================================================== > --- linux-2.6.orig/include/linux/highmem.h 2010-11-22 14:43:40.000000000 -0600 > +++ linux-2.6/include/linux/highmem.h 2010-11-22 14:45:02.000000000 -0600 > @@ -81,7 +81,8 @@ DECLARE_PER_CPU(int, __kmap_atomic_idx); > > static inline int kmap_atomic_idx_push(void) > { > - int idx = __get_cpu_var(__kmap_atomic_idx)++; > + int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1; > + > #ifdef CONFIG_DEBUG_HIGHMEM > WARN_ON_ONCE(in_irq() && !irqs_disabled()); > BUG_ON(idx > KM_TYPE_NR); > @@ -91,12 +92,12 @@ static inline int kmap_atomic_idx_push(v > > static inline int kmap_atomic_idx(void) > { > - return __get_cpu_var(__kmap_atomic_idx) - 1; > + return __this_cpu_read(__kmap_atomic_idx) - 1; > } > > static inline int kmap_atomic_idx_pop(void) > { > - int idx = --__get_cpu_var(__kmap_atomic_idx); > + int idx = __this_cpu_dec_return(__kmap_atomic_idx); __this_cpu_dec_return() is only needed if CONFIG_DEBUG_HIGHMEM > #ifdef CONFIG_DEBUG_HIGHMEM > BUG_ON(idx < 0); > #endif > You could change kmap_atomic_idx_pop() to return void, and use __this_cpu_dec(__kmap_atomic_idx) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org