Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753737AbaATPv4 (ORCPT ); Mon, 20 Jan 2014 10:51:56 -0500 Received: from mail-ea0-f180.google.com ([209.85.215.180]:60293 "EHLO mail-ea0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbaATPvx (ORCPT ); Mon, 20 Jan 2014 10:51:53 -0500 Date: Mon, 20 Jan 2014 16:51:46 +0100 From: Frederic Weisbecker To: Viresh Kumar Cc: Thomas Gleixner , Peter Zijlstra , Linux Kernel Mailing List , Lists linaro-kernel , Steven Rostedt , Linaro Networking Subject: Re: [QUERY]: Is using CPU hotplug right for isolating CPUs? Message-ID: <20140120155145.GB9436@localhost.localdomain> References: <20140115171704.GB21574@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2014 at 05:00:20PM +0530, Viresh Kumar wrote: > On 16 January 2014 15:16, Thomas Gleixner wrote: > > Just do the math. > > > > max reload value / timer freq = max time span > > Thanks. > > > So: > > > > 0x7fffffff / 24MHz = 89.478485 sec > > > > Nothing to do here except to get rid of the requirement to arm the > > timer at all. > > @Frederic: Any inputs on how to get rid of this timer here? I fear you can't. If you schedule a timer in 4 seconds away and your clockdevice can only count up to 2 seconds, you can't help much the interrupt in the middle to cope with the overflow. So you need to act on the source of the timer: * identify what cause this timer * try to turn that feature off * if you can't then move the timer to the housekeeping CPU I'll have a look into the latter point to affine global timers to the housekeeping CPU. Per cpu timers need more inspection though. Either we rework them to be possibly handled by remote/housekeeping CPUs, or we let the associate feature to be turned off. All in one it's a case by case work. -- 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/