Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S271083AbUJUXRP (ORCPT ); Thu, 21 Oct 2004 19:17:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S271080AbUJUXLd (ORCPT ); Thu, 21 Oct 2004 19:11:33 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:14572 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S271067AbUJUXHT (ORCPT ); Thu, 21 Oct 2004 19:07:19 -0400 Subject: How is user space notified of CPU speed changes? From: Lee Revell To: linux-kernel Cc: Robert Love Content-Type: text/plain Message-Id: <1098399709.4131.23.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Thu, 21 Oct 2004 19:01:49 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 901 Lines: 22 This issue came up on the JACK (http://jackit.sf.net) mailing list. Google was not helpful so I ask here. JACK needs to know the CPU speed, in order to calculate the DSP load among other things. It used to be a valid assumption that you could calculate it on startup and it would not change. Now with frequency scaling (apparently desktops do this as well as laptops) this doesn't work anymore. Is there a sane way for jackd to be notified when the CPU speed changes? Polling a file in /sys is not good enough, the overhead is unacceptable and we need to know _now_. Is this the kind of thing that would require the new kernel event interface? 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/