Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754363AbaAUKeB (ORCPT ); Tue, 21 Jan 2014 05:34:01 -0500 Received: from mail-oa0-f48.google.com ([209.85.219.48]:39678 "EHLO mail-oa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754313AbaAUKdy (ORCPT ); Tue, 21 Jan 2014 05:33:54 -0500 MIME-Version: 1.0 In-Reply-To: <20140120155145.GB9436@localhost.localdomain> References: <20140115171704.GB21574@localhost.localdomain> <20140120155145.GB9436@localhost.localdomain> Date: Tue, 21 Jan 2014 16:03:53 +0530 Message-ID: Subject: Re: [QUERY]: Is using CPU hotplug right for isolating CPUs? From: Viresh Kumar To: Frederic Weisbecker Cc: Thomas Gleixner , Peter Zijlstra , Linux Kernel Mailing List , Lists linaro-kernel , Steven Rostedt , Linaro Networking Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20 January 2014 21:21, Frederic Weisbecker wrote: > 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 So, the main problem in my case was caused by this: <...>-2147 [001] d..2 302.573881: hrtimer_start: hrtimer=c172aa50 function=tick_sched_timer expires=602075000000 softexpires=602075000000 I have mentioned this earlier when I sent you attachments. I think this is somehow tied with the NO_HZ_FULL stuff? As the timer is queued for 300 seconds after current time. How to get this out? > 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. Which CPUs are housekeeping CPUs? How do we declare them? -- 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/