From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753208AbbHMPgT (ORCPT ); Thu, 13 Aug 2015 11:36:19 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:37694 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751820AbbHMPgS (ORCPT ); Thu, 13 Aug 2015 11:36:18 -0400 Date: Thu, 13 Aug 2015 17:36:15 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: Vatika Harlalka , mingo@redhat.com, tglx@linutronix.de, rafael.j.wysocki@intel.com, schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org, preetium@andrew.cmu.edu, preeti.murthy@gmail.com Subject: Re: [PATCH 0/2] nohz_full: Offload task_tick to remote housekeeping cpus for nohz_full cpus Message-ID: <20150813153614.GD29958@lerouge> References: <20150813122223.GC16853@twins.programming.kicks-ass.net> <20150813124401.GA29958@lerouge> <20150813150545.GD16853@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150813150545.GD16853@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 13, 2015 at 05:05:45PM +0200, Peter Zijlstra wrote: > On Thu, Aug 13, 2015 at 02:44:02PM +0200, Frederic Weisbecker wrote: > > On Thu, Aug 13, 2015 at 02:22:23PM +0200, Peter Zijlstra wrote: > > > On Thu, Aug 13, 2015 at 02:55:36PM +0530, Vatika Harlalka wrote: > > > > This patchset is for offloading task_tick() to a remote housekeeping > > > > cpu. The larger aim is to stop ticks on nohz_full cpus. For this, extra > > > > work must be done by housekeeping cpus. So, task_tick is called from a > > > > delayed workqueue for nohz_full cpus and the work is requeued every second > > > > for those nohz_full cpus whose ticks are stopped while they are busy. In > > > > the rest of the cases it will lead to redundant accounting. To facilitate > > > > this, a new function tick_nohz_remote_tick_stopped is added to indicate > > > > whether ticks are stopped on a remote cpu. > > > > Tick related code in core.c is moved to tick.c > > > > > > *sigh* of course you didn't read what I've written on this topic.. > > > > What is it? Note Vatika wrote this after my suggestion, so if there is an issue, > > I'm likely the responsible :-) But I don't recall you opposed to this solution. > > *sigh* of course you _could_ all use Google yourselves. > > Re-read: https://patches.linaro.org/28290/ Sorry, there were dozens of threads about this issue and I got a bit confused. > > I see nothing like the stuff I asked for in here, on top it creates the > stupid tick.c file. Right. I initially thought that we should make sched_tick() just work with long delays. Then tglx suggested the offline idea but I lost track about our conversation. But yeah making that scheduler_tick() working with long delays sound much better. Certainly much more work but that's a natural evolution after all. It should pay in longer term. We can start with update_cpu_load_active() which only works with HZ frequency updates or nohz idle zero load decay. Now I think that stuff is only used for load balancing. I had hopes this thing could be removed. I think Alex Shin (IIRC) tried but the patchset didn't make it. Thanks.