linux-kernel - Re: [PATCH] Prevent users from disabling tickless

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Message-Id: <201012220138.08105.rjw@sisk.pl>
Date:	Wed, 22 Dec 2010 01:38:07 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Prevent users from disabling tickless

On Wednesday, December 22, 2010, Matthew Wilcox wrote:
> On Wed, Dec 22, 2010 at 12:46:23AM +0100, Rafael J. Wysocki wrote:
> > On Wednesday, December 22, 2010, Matthew Wilcox wrote:
> > > 
> > > Disabling NO_HZ has a serious negative effect on performance -- an extra
> > > 70us per I/O.  Prevent users from deselecting it.
> > > 
> > > Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
> > 
> > OTOH, it causes some systems to not work at all still.  Sadly.
> 
> It doesn't stop people from specifying nohz=off on the kernel command line.

Which still doesn't work for some people AFAICT.

Thanks,
Rafael
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