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From: Andi Kleen <andi@firstfloor.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>,
	linux-kernel@vger.kernel.org, mingo@elte.hu,
	laijs@cn.fujitsu.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
	peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com,
	edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
	sbw@mit.edu
Subject: Re: [PATCH RFC nohz_full 0/7] v2 Provide infrastructure for full-system idle
Date: Mon, 1 Jul 2013 18:19:10 +0200	[thread overview]
Message-ID: <20130701161910.GN6123@two.firstfloor.org> (raw)
In-Reply-To: <20130701160314.GM3773@linux.vnet.ibm.com>

> I am guessing that you want CONFIG_NO_HZ_FULL to implicitly enable
> the sysidle code so that CONFIG_NO_HZ_FULL_SYSIDLE can be eliminated.
> I will be happy to take that step, but only after I gain full confidence
> in the correctness and performance of the sysidle code.

FWIW if you want useful testing you need to enable it by default
(as part of NO_IDLE_HZ) anyways. Users will most likely pick
whatever is "default" in Kconfig.

> > If you want a switch for testing I would advise a sysctl or sysfs knob
> 
> This would work well for the correctness part, but not for the performance
> part.

What performance part? 

Are you saying this adds so many checks to hot paths that normal runtime
if() with a flag is too expensive?

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.

  reply	other threads:[~2013-07-01 16:19 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-28 20:09 Paul E. McKenney
2013-06-28 20:10 ` [PATCH RFC nohz_full v2 1/7] nohz_full: Add Kconfig parameter for scalable detection of all-idle state Paul E. McKenney
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 2/7] nohz_full: Add rcu_dyntick data " Paul E. McKenney
2013-07-01 15:31     ` Josh Triplett
2013-07-01 15:52       ` Paul E. McKenney
2013-07-01 18:16         ` Josh Triplett
2013-07-01 18:23           ` Paul E. McKenney
2013-07-01 18:34             ` Josh Triplett
2013-07-01 19:16               ` Paul E. McKenney
2013-07-02  5:10                 ` Mike Galbraith
2013-07-02  5:58                   ` Paul E. McKenney
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 3/7] nohz_full: Add per-CPU idle-state tracking Paul E. McKenney
2013-07-01 15:33     ` Josh Triplett
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 4/7] nohz_full: Add full-system idle states and variables Paul E. McKenney
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 5/7] nohz_full: Add full-system-idle arguments to API Paul E. McKenney
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 6/7] nohz_full: Add full-system-idle state machine Paul E. McKenney
2013-07-01 16:35     ` Frederic Weisbecker
2013-07-01 18:10       ` Paul E. McKenney
2013-07-01 20:55         ` Frederic Weisbecker
2013-07-01 16:53     ` Frederic Weisbecker
2013-07-01 18:17       ` Paul E. McKenney
2013-07-01 21:38     ` Frederic Weisbecker
2013-07-01 22:51       ` Paul E. McKenney
2013-06-28 20:10   ` [PATCH RFC nohz_full v2 7/7] nohz_full: Force RCU's grace-period kthreads onto timekeeping CPU Paul E. McKenney
2013-07-01 15:19 ` [PATCH RFC nohz_full 0/7] v2 Provide infrastructure for full-system idle Andi Kleen
2013-07-01 16:03   ` Paul E. McKenney
2013-07-01 16:19     ` Andi Kleen [this message]
2013-07-01 19:19       ` Paul E. McKenney
2013-07-01 19:43 ` Christoph Lameter
2013-07-01 19:56   ` Paul E. McKenney
2013-07-01 20:24     ` Christoph Lameter
2013-07-01 20:43       ` Thomas Gleixner

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