Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965111AbWIRPPQ (ORCPT ); Mon, 18 Sep 2006 11:15:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751764AbWIRPPQ (ORCPT ); Mon, 18 Sep 2006 11:15:16 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:62421 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751763AbWIRPPO (ORCPT ); Mon, 18 Sep 2006 11:15:14 -0400 Date: Mon, 18 Sep 2006 17:06:50 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Andrew Morton , Chuck Ebbert <76306.1226@compuserve.com>, In Cognito , linux-kernel , Andi Kleen Subject: Re: Sysenter crash with Nested Task Bit set Message-ID: <20060918150650.GA10336@elte.hu> References: <200609172354_MC3-1-CB7A-58ED@compuserve.com> <20060917222537.55241d19.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-SpamScore: -2.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.9 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 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] -0.1 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 Content-Length: 873 Lines: 20 * Linus Torvalds wrote: > And sysenter really is very special because of the weak trap > semantics. Damn. We could either fix it in the sysenter code-path, or > in the task-switch one, and both of them are timing-critical, but task > switching perhaps just a tad less so. agreed. Context-switching is 10 times less frequent on most workloads than syscalls, so if it takes 10 cycles in the context-switch path to eliminate a 1 cycle overhead in the syscall-entry path then we are still break-even on average. In this case the overhead is similar i think, so the switch_to() fix is preferable. 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/