linux-kernel - Re: [GIT PULL] nohz: Bunch of fixes

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Date:	Sat, 4 May 2013 08:41:51 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] nohz: Bunch of fixes


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> Ingo,
> 
> Please pull the timers/nohz-hz1 branch that can be found at:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> 	timers/nohz-hz1
> 
> HEAD: a7f4d69bb1d5e1f573b680355a2ad51566338887
> 
> It fixes a Kconfig dependency issue and forces a minimum of 1 tick every seconds
> to keep handling the scheduler_tick() duties, even at a very low granularity. This
> is a workaround until we can handle all these duties through on-demand driven
> solutions rather than using periodic events, as per your suggestion.
> 
> I just noted two things:
> 
> * update_cpu_load_active() seem to rely on the fixed periodic tick at the
>   HZ rate. There is certainly something to tweak there to make it really correct
>   with dynamick ticks. I have the feeling that modifying pending_updates won't work
>   as it seems to decay assuming the time to catch up was idle.
> 
> * I'll probably have to disable CONFIG_CFS_BANDWIDTH when full dynticks
>   is enabled. First of all it modifies rq->nr_running without using inc/dec_nr_running
>   standard API, which is required for full dynticks. And second, I need to triple
>   check it's safe to use with 1 tick per second.
> 
> Ah and please note the merge commit (c032862fba51a3ca504752d3a25186b324c5ce83)
> that was needed to get latest RCU and sched updates for the Kconfig fix.
> 
> Thanks,
> 	Frederic
> ---
> 
> Frederic Weisbecker (2):
>       rcu: Fix full dynticks' dependency on wide RCU nocb mode
>       sched: Keep at least 1 tick per second for active dynticks tasks
> 
> 
>  include/linux/sched.h    |    1 +
>  init/Kconfig             |    4 ++--
>  kernel/sched/core.c      |   30 ++++++++++++++++++++++++++++++
>  kernel/sched/idle_task.c |    1 +
>  kernel/sched/sched.h     |   10 ++++++++++
>  kernel/time/Kconfig      |    1 -
>  kernel/time/tick-sched.c |    7 +++++++
>  7 files changed, 51 insertions(+), 3 deletions(-)

Pulled, thanks Frederic!

	Ingo
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