From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751584Ab3KPHDU (ORCPT ); Sat, 16 Nov 2013 02:03:20 -0500 Received: from mail-ee0-f46.google.com ([74.125.83.46]:36817 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751208Ab3KPHDR (ORCPT ); Sat, 16 Nov 2013 02:03:17 -0500 Date: Sat, 16 Nov 2013 08:03:05 +0100 From: Richard Cochran To: Miroslav Lichvar Cc: John Stultz , linux-kernel@vger.kernel.org, Prarit Bhargava Subject: Re: [PATCH RFC] timekeeping: Fix clock stability with nohz Message-ID: <20131116070304.GB4355@netboy> References: <1384440640-9482-1-git-send-email-mlichvar@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1384440640-9482-1-git-send-email-mlichvar@redhat.com> 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 Thu, Nov 14, 2013 at 03:50:40PM +0100, Miroslav Lichvar wrote: > include/linux/timekeeper_internal.h | 4 + > kernel/time/timekeeping.c | 209 +++++------------------------------- > 2 files changed, 31 insertions(+), 182 deletions(-) This looks like an impressive simplification... > - * So the following can be confusing. Yep. So I really have no idea how the deleted code worked (or didn't work for nohz), but I can confirm that nohz time keeping is broken under light system load. Running a high load (like recompiling the kernel on all cores for CONFIG_HZ_PERIODIC=y ;) hides the issue, but that is obviously not the right solution. Out of my ignorance, two questions spring to mind. 1. Considering the simplicity of Miroslav's patch, what was the benefit of the much more complicated code in the first place? 2. Does this patch work in the CONFIG_HZ_PERIODIC case just as well as the deleted code? Thanks, Richard