Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261322AbUJWWW3 (ORCPT ); Sat, 23 Oct 2004 18:22:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261324AbUJWWW2 (ORCPT ); Sat, 23 Oct 2004 18:22:28 -0400 Received: from clock-tower.bc.nu ([81.2.110.250]:7810 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S261322AbUJWWWS (ORCPT ); Sat, 23 Oct 2004 18:22:18 -0400 Subject: Re: How is user space notified of CPU speed changes? From: Alan Cox To: Lee Revell Cc: Linux Kernel Mailing List , Robert Love In-Reply-To: <1098508238.13176.17.camel@krustophenia.net> References: <1098399709.4131.23.camel@krustophenia.net> <1098444170.19459.7.camel@localhost.localdomain> <1098508238.13176.17.camel@krustophenia.net> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1098566366.24804.8.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Date: Sat, 23 Oct 2004 22:19:28 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 763 Lines: 19 On Sad, 2004-10-23 at 06:10, Lee Revell wrote: > JACK makes extensive use of microsecond-level timers. These must be > calibrated at startup, and recalibrated when the CPU speed changes. How > does JACK register with the kernel to be notified when the CPU speed > changes? It did - The kernel doesn't always know - CPU speed is meaningless in hyper-threading since performance is not x2 for two cores but instead varies - It doesn't handle split CPU speed SMP - where CPU speeds vary - God help you if virtualised - 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/