From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423980AbcFMOcx (ORCPT ); Mon, 13 Jun 2016 10:32:53 -0400 Received: from www.linutronix.de ([62.245.132.108]:57281 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423580AbcFMOcw (ORCPT ); Mon, 13 Jun 2016 10:32:52 -0400 Date: Mon, 13 Jun 2016 16:30:52 +0200 (CEST) From: Thomas Gleixner To: Eric Dumazet cc: Peter Zijlstra , LKML , Ingo Molnar , "Paul E. McKenney" , Frederic Weisbecker , Chris Mason , Arjan van de Ven , rt@linutronix.de Subject: Re: [patch 13/20] timer: Switch to a non cascading wheel In-Reply-To: Message-ID: References: <20160613070440.950649741@linutronix.de> <20160613075929.282143900@linutronix.de> <20160613114005.GY30909@twins.programming.kicks-ass.net> 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,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 Jun 2016, Eric Dumazet wrote: > On Mon, Jun 13, 2016 at 5:30 AM, Thomas Gleixner wrote: > > On Mon, 13 Jun 2016, Peter Zijlstra wrote: > >> On Mon, Jun 13, 2016 at 08:41:00AM -0000, Thomas Gleixner wrote: > >> > + > >> > + /* Cascading, sigh... */ > >> > >> So given that userspace has no influence on timer period; can't we > >> simply fail to support timers longer than 30 minutes? > >> > >> In anything really arming timers _that_ long? > > > > Unfortunately yes. Networking being one of those. Real cascading happens once > > in a blue moon, but it happens. > > > Anyway, for the more common HZ=1000 case, what would the 'limit' be ? 34 minutes with the currently chosen parameters.