Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261500AbVDGOwI (ORCPT ); Thu, 7 Apr 2005 10:52:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262476AbVDGOwI (ORCPT ); Thu, 7 Apr 2005 10:52:08 -0400 Received: from mx1.elte.hu ([157.181.1.137]:25307 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S261500AbVDGOwE (ORCPT ); Thu, 7 Apr 2005 10:52:04 -0400 Date: Thu, 7 Apr 2005 16:51:50 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Andrew Morton , stsp@aknet.ru, linux-kernel@vger.kernel.org, VANDROVE@vc.cvut.cz Subject: Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC Message-ID: <20050407145150.GA6215@elte.hu> References: <20050405065544.GA21360@elte.hu> <4252E2C9.9040809@aknet.ru> <4252EA01.7000805@aknet.ru> <425403F6.409@aknet.ru> <20050407080004.GA27252@elte.hu> <20050407041006.4c9db8b2.akpm@osdl.org> 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-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1045 Lines: 25 * Linus Torvalds wrote: > > > pushfl > After all, I very strongly suspect that we don't actually really > _care_ if eflags stays the same over a system call, and I could see > that some dynamic CPU's might prefer not having to push an eflags > value that just got changed by the "sti", so it _might_ save several > cycles to avoid that dependency, and also obviously avoid a subtle > dependency on a sw level that the previous patch clearly introduced. > > Anybody willing to time it? ;) i can tell you without any measurement that pushfl is slower by a couple of cycles than a simple pushl $0x00010046, on basically all x86 CPUs. And since we only support SYENTER from 32-bit mode and we dont guarantee flags to be saved, it isnt all that incorrect to do? Ingo - 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/