From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964990AbWGFIVR (ORCPT ); Thu, 6 Jul 2006 04:21:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964991AbWGFIVR (ORCPT ); Thu, 6 Jul 2006 04:21:17 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:908 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S964990AbWGFIVQ (ORCPT ); Thu, 6 Jul 2006 04:21:16 -0400 Date: Thu, 6 Jul 2006 10:16:39 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Andrew Morton , linux-kernel@vger.kernel.org, arjan@infradead.org Subject: [patch] spinlocks: remove 'volatile' Message-ID: <20060706081639.GA24179@elte.hu> References: <20060705114630.GA3134@elte.hu> <20060705101059.66a762bf.akpm@osdl.org> <20060705193551.GA13070@elte.hu> <20060705131824.52fa20ec.akpm@osdl.org> <20060705204727.GA16615@elte.hu> <20060705214502.GA27597@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -3.1 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-3.1 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] 0.2 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > I wonder if we should remove the "volatile". There really isn't > anything _good_ that gcc can do with it, but we've seen gcc code > generation do stupid things before just because "volatile" seems to > just disable even proper normal working. yeah. I tried this and it indeed slashed 42K off text size (0.2%): text data bss dec filename 20779489 6073834 3075176 29928499 vmlinux.volatile 20736884 6073834 3075176 29885894 vmlinux.non-volatile i booted the resulting allyesconfig bzImage and everything seems to be working fine. Find patch below. Ingo ------------------> Subject: spinlocks: remove 'volatile' From: Ingo Molnar remove 'volatile' from the spinlock types, it causes gcc to generate really bad code. (and it's pointless anyway) this reduces the non-debug SMP kernel's size by 0.2% (!). Signed-off-by: Ingo Molnar --- include/asm-i386/spinlock_types.h | 4 ++-- include/asm-x86_64/spinlock_types.h | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) Index: linux/include/asm-i386/spinlock_types.h =================================================================== --- linux.orig/include/asm-i386/spinlock_types.h +++ linux/include/asm-i386/spinlock_types.h @@ -6,13 +6,13 @@ #endif typedef struct { - volatile unsigned int slock; + unsigned int slock; } raw_spinlock_t; #define __RAW_SPIN_LOCK_UNLOCKED { 1 } typedef struct { - volatile unsigned int lock; + unsigned int lock; } raw_rwlock_t; #define __RAW_RW_LOCK_UNLOCKED { RW_LOCK_BIAS } Index: linux/include/asm-x86_64/spinlock_types.h =================================================================== --- linux.orig/include/asm-x86_64/spinlock_types.h +++ linux/include/asm-x86_64/spinlock_types.h @@ -6,13 +6,13 @@ #endif typedef struct { - volatile unsigned int slock; + unsigned int slock; } raw_spinlock_t; #define __RAW_SPIN_LOCK_UNLOCKED { 1 } typedef struct { - volatile unsigned int lock; + unsigned int lock; } raw_rwlock_t; #define __RAW_RW_LOCK_UNLOCKED { RW_LOCK_BIAS }