Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751157AbXBVNZV (ORCPT ); Thu, 22 Feb 2007 08:25:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751591AbXBVNZV (ORCPT ); Thu, 22 Feb 2007 08:25:21 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:33134 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751157AbXBVNZT (ORCPT ); Thu, 22 Feb 2007 08:25:19 -0500 Subject: Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1] From: Arjan van de Ven To: Jan Engelhardt Cc: Thomas Gleixner , Luca Tettamanti , linux-kernel@vger.kernel.org In-Reply-To: References: <20070221230409.GA1158@dreamland.darkstar.lan> <1172099859.25076.132.camel@localhost.localdomain> Content-Type: text/plain Organization: Intel International BV Date: Thu, 22 Feb 2007 14:25:12 +0100 Message-Id: <1172150712.3531.265.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2.1 (2.8.2.1-3.fc6) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 33 > What's the benefit of doing so - and why has not it been done before? > I mean, I run a regular 2.6.18.6, > /sys/devices/system/clocksource/clocksource0/current_clocksource (is this > related?) shows "acpi_pm", but the IRQ0 counter increases at HZ. Maybe I > am confusing things, but why the need for PIT when clocksource is acpi_pm > anyway? you're mixing up 2 concepts: 1) clocksource 2) eventsource 1) is for "what time is it now", and acpi_pm is useful for that, as are several other things such as rdtsc 2) is for "I need THIS to happen X miliseconds from now". acpi_pm is not useful for that, nor is rdtsc. some can be used for both (PIT), but on a concept level the uses are independent. The advantage of local apic over PIT is that local apic is cheap to do "one shot" future events with, while the PIT will tick periodic at a fixed frequency. With tickless idle.. that's not what you want. -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - 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/