Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261463AbVEODT0 (ORCPT ); Sat, 14 May 2005 23:19:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261460AbVEODT0 (ORCPT ); Sat, 14 May 2005 23:19:26 -0400 Received: from twinlark.arctic.org ([207.7.145.18]:22976 "EHLO twinlark.arctic.org") by vger.kernel.org with ESMTP id S261466AbVEODTW (ORCPT ); Sat, 14 May 2005 23:19:22 -0400 Date: Sat, 14 May 2005 20:19:21 -0700 (PDT) From: dean gaudet To: Arjan van de Ven cc: Lee Revell , Alan Cox , Dave Jones , Matt Mackall , Andy Isaacson , Andi Kleen , "Richard F. Rebel" , Gabor MICSKO , Linux Kernel Mailing List , tytso@mit.edu Subject: Re: Hyper-Threading Vulnerability In-Reply-To: <1116100126.6007.17.camel@laptopd505.fenrus.org> Message-ID: References: <1115963481.1723.3.camel@alderaan.trey.hu> <1116009483.4689.803.camel@rebel.corp.whenu.com> <20050513190549.GB47131@muc.de> <20050513212620.GA12522@hexapodia.org> <20050513215905.GY5914@waste.org> <1116024419.20646.41.camel@localhost.localdomain> <1116025212.6380.50.camel@mindpipe> <20050513232708.GC13846@redhat.com> <1116027488.6380.55.camel@mindpipe> <1116084186.20545.47.camel@localhost.localdomain> <1116088229.8880.7.camel@mindpipe> <1116089068.6007.13.camel@laptopd505.fenrus.org> <1116093396.9141.11.camel@mindpipe> <1116093694.6007.15.camel@laptopd505.fenrus.org> <1116098504.9141.31.camel@mindpipe> <1116100126.6007.17.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1005 Lines: 23 On Sat, 14 May 2005, Arjan van de Ven wrote: > it's a matter of time (my estimate is a year or two) before processors > get variable frequencies based on temperature targets etc... > and then rdtsc is really useless for this kind of thing.. what do you mean "a year or two"? processors have been doing this for many years now. i'm biased, but i still think transmeta did this the right way... the tsc operates at the top frequency of the processor always. i do a hell of a lot of microbenchmarking on various processors and i always use tsc -- but i'm just smart enough to take multiple samples and i try to make each sample smaller than a time slice... which avoids most of the pitfalls, and would even work on smp boxes with tsc differences. -dean - 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/