Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262187AbUJZDUN (ORCPT ); Mon, 25 Oct 2004 23:20:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262121AbUJZCxA (ORCPT ); Mon, 25 Oct 2004 22:53:00 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:43954 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S262163AbUJZCio (ORCPT ); Mon, 25 Oct 2004 22:38:44 -0400 Subject: Re: How is user space notified of CPU speed changes? From: Lee Revell To: Alan Cox Cc: Linux Kernel Mailing List , Robert Love In-Reply-To: <1098626510.24073.9.camel@localhost.localdomain> References: <1098399709.4131.23.camel@krustophenia.net> <1098444170.19459.7.camel@localhost.localdomain> <1098508238.13176.17.camel@krustophenia.net> <1098566366.24804.8.camel@localhost.localdomain> <1098571334.29081.21.camel@krustophenia.net> <1098626510.24073.9.camel@localhost.localdomain> Content-Type: text/plain Date: Mon, 25 Oct 2004 22:38:43 -0400 Message-Id: <1098758323.9166.3.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 796 Lines: 18 On Sun, 2004-10-24 at 15:02 +0100, Alan Cox wrote: > Are you trying to use tsc for delays or measure CPU speed. The original > question you asked was about CPU speed and the two are very different. No we are only using it as a cheap way to do microsecond level timing. Are you saying we should just use gettimeofday() instead? jack_get_microseconds() is called at least twice per period which can be several thousand times per second. Is the overhead of a system call really low enough that this should work? rdtsc is definitely cheap enough. Lee - 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/