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From: Serge Belyshev <belyshev@depni.sinp.msu.ru>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Prevent users from disabling tickless
References: <20101221233942.GL1263@parisc-linux.org>
Date: Sun, 02 Jan 2011 10:59:38 +0000
In-Reply-To: <20101221233942.GL1263@parisc-linux.org> (Matthew Wilcox's
	message of "Tue, 21 Dec 2010 16:39:43 -0700")
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Matthew Wilcox <matthew@wil.cx> writes:

> Disabling NO_HZ has a serious negative effect on performance -- an extra
> 70us per I/O.  Prevent users from deselecting it.

This is rather non-trivial change.

The common wisdom was that NO_HZ=y *adds* overhead, not removes it.
Thus, I propose:

(1) Retaining and elaborating the help text.
(2) Allow user to change the default.