Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755125AbZCMIto (ORCPT ); Fri, 13 Mar 2009 04:49:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752331AbZCMItf (ORCPT ); Fri, 13 Mar 2009 04:49:35 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:40405 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751603AbZCMIte (ORCPT ); Fri, 13 Mar 2009 04:49:34 -0400 Subject: Re: System tick rate From: Peter Zijlstra To: Jan Engelhardt Cc: Arjan van de Ven , Linux Kernel Mailing List In-Reply-To: References: <20090312072110.0a325543@infradead.org> Content-Type: text/plain Date: Fri, 13 Mar 2009 09:49:27 +0100 Message-Id: <1236934167.5188.195.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.25.92 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1263 Lines: 31 On Thu, 2009-03-12 at 15:45 +0100, Jan Engelhardt wrote: > On Thursday 2009-03-12 15:21, Arjan van de Ven wrote: > >On Thu, 12 Mar 2009 14:38:19 +0100 (CET) Jan Engelhardt wrote: > >> > >> is there an "official" way of obtaining the current tick rate when > >> CONFIG_NO_HZ? > > > >what does "current tick rate" mean for you in a no-hz situation ? > >is it the HZ value (which is supposed to be invisible from userspace, > >so good luck) or the wakeup count ? > > Hm, I guess what I want is the number of timer interrupts which > occurred within the observation period that called the scheduler > code. (So that excludes RTC on usual x86en.) There is no tick rate with NO_HZ mode, only a max tick rate, but as Arjan said, not even that is exposed to user-space. I think Dave's Niagra has the crown here, because he ran into some bug in the NO_HZ code some while back because he idled longer than we ever seen before. I think it was in the order of 30 minutes or something without a single wakeup of the CPU. -- 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/