linux-kernel - Re: [PATCH RFC tip/core/rcu] accelerate grace period if last non-dynticked CPU

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Message-ID: <873a1sft9q.fsf@basil.nowhere.org>
Date:	Tue, 26 Jan 2010 22:30:57 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	dvhltc@...ibm.com, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com
Subject: Re: [PATCH RFC tip/core/rcu] accelerate grace period if last non-dynticked CPU

"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> writes:

Kind of offtopic to the original patch, but I couldn't 
resist...

> +config RCU_FAST_NO_HZ
> +	bool "Accelerate last non-dyntick-idle CPU's grace periods"
> +	depends on TREE_RCU && NO_HZ && SMP

Having such a thing as a config option doesn't really make 
any sense to me. Who would want to recompile their kernel
to enable/disable this? If anything it should be runtime, or better
just unconditionally on.

In general RCU could probably reduce its number of "weird"
Kconfig options.

While I think I have a better understanding of RCU than a lot
of normal users I often have no clue what to set there when
building a kernel.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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