Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753238AbbHVO34 (ORCPT ); Sat, 22 Aug 2015 10:29:56 -0400 Received: from www.linutronix.de ([62.245.132.108]:42524 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752455AbbHVO3z (ORCPT ); Sat, 22 Aug 2015 10:29:55 -0400 Date: Sat, 22 Aug 2015 16:29:27 +0200 (CEST) From: Thomas Gleixner To: William Breathitt Gray cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org Subject: Re: Regarding USER_HZ and the exposure of kernel jiffies in userspace In-Reply-To: <55D880F3.4030909@gmail.com> Message-ID: References: <55D880F3.4030909@gmail.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 990 Lines: 27 On Sat, 22 Aug 2015, William Breathitt Gray wrote: > I believe the error in my understanding is the assumption that _all_ > instances of kernel jiffies exposure in userspace should be scaled; but > it appears that not all instances are. When are kernel jiffies meant to > be scaled via USER_HZ, and when are they not? All instances which are de facto APIs, syscalls and also various files in proc/ must be in USER_HZ because userspace applications depend on the USER_HZ value. proc/timer_list is exempt from that because its more a debugging interface which is not part of the strict kernel API. And we really want to see the real values and not the scaled USER_HZ ones for that purpose. I hope that answers your question. Thanks, tglx -- 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/