linux-kernel - Re: [PATCH tip/core/rcu 0/12] RCU Kconfig fixes for v4.2

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Date:	Wed, 22 Apr 2015 01:26:09 -0400
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	David Howells <dhowells@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH tip/core/rcu 0/12] RCU Kconfig fixes for v4.2

On Tue, Apr 21, 2015 at 3:55 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> Hello!
>
> This patch series reduces the number of questions that RCU asks Kconfig
> users.  After this series is applied, removing the RCU-related definitions
> from .config and running "make oldconfig" results in only the following:
>
> RCU Implementation
>> 1. Tree-based hierarchical RCU (TREE_RCU) (NEW)
> choice[1]: 1
> Make expert-level adjustments to RCU configuration (RCU_EXPERT) [N/y/?] (NEW)
>
> Those expert users wishing to tune RCU answer Y to this question.
>
> The patches in this series are as follows:
>
> 1.      Drive TASKS_RCU directly from Kconfig, for example, by having
>         RCU_TORTURE_TESTS select it.
>
> 2.      Remove CONFIG_TASKS_RCU=y from the three TASKS_RCU test
>         scenarios, since this is set by virtue of having rcutorture
>         configured.
>
> 3.      Drive RCU_USER_QS directly from Kconfig, relying on the fact
>         that NO_HZ_FULL selects it.
>
> 4.      Convert CONFIG_RCU_FANOUT_EXACT to a boot parameter, where it
>         is used by rcutorture.
>
> 5.      Update rcutorture test scenarios to use the boot parameter
>         created in #4 instead of the Kconfig parameter.
>
> 6.      Create a boot parameter to do a diagnostic dump of the shape
>         of the rcu_node combining tree, which is useful for verifying
>         that intended changes to that tree actually happened.
>
> 7.      Create an RCU_EXPERT Kconfig parameter and hide the
>         RCU_FAST_NO_HZ, RCU_BOOST, CONTEXT_TRACKING_FORCE, and
>         RCU_NOCB_CPU boolean parameters behind it.
>
> 8.      Make rcutorture test scenarios force RCU_EXPERT, but have
>         SRCU-P, TASKS03, and TREE09 retain !RCU_EXPERT in order to
>         test the vanilla configuration.
>
> 9.      Remove the dependency of RCU_FANOUT_LEAF on RCU_FANOUT.
>
> 10.     Change RCU to allow it to tolerate an undefined RCU_FANOUT,
>         and then hide RCU_FANOUT behind RCU_EXPERT.
>
> 11.     Change RCU to allow it to tolerate an undefined RCU_FANOUT_LEAF,
>         and then hide RCU_FANOUT_LEAF behind RCU_EXPERT.
>
> 12.     Change RCU to allow it to tolerate an undefined RCU_KTHREAD_PRIO,
>         and then hide RCU_KTHREAD_PRIO behind RCU_EXPERT.
>
>                                                         Thanx, Paul
>

With or without the minor changes:

Reviewed-by: Pranith Kumar <bobby.prani@...il.com>

-- 
Pranith
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