linux-kernel - Re: (BUG?) round_jiffies() is non-monotonic on SMP

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Message-ID: <20081101194357.1810f57a@infradead.org>
Date:	Sat, 1 Nov 2008 19:43:57 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: (BUG?) round_jiffies() is non-monotonic on SMP

On Sat, 1 Nov 2008 22:36:30 -0400 (EDT)
Alan Stern <stern@...land.harvard.edu> wrote:

> On Sat, 1 Nov 2008, Arjan van de Ven wrote:
> 
> > > Come to think of it, is there any good reason why
> > > round_jiffies() doesn't always round up?  It seems a lot safer.
> > 
> > at the time folks had concerns about making a big error in that
> > direction...
> 
> All right then.  Would it be preferable to add a new
> round_jiffies_up() routine, or to change round_jiffies() so that it
> never rounds down?

I'd prefer the former.
But to be honest.. I would even more prefer the use of range timers ;)
They're in 2.6.28-rc now ... and more power friendly than rounded timers
(although I will readily admit that rounding is just easier)



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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