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Date: Thu, 4 Sep 2008 10:30:49 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <peterz@infradead.org>,
       Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>,
       Ben Hutchings <bhutchings@solarflare.com>,
       Jesse Barnes <jbarnes@virtuousgeek.org>, linux-kernel@vger.kernel.org,
       netdev@vger.kernel.org, linux-pci@vger.kernel.org,
       Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: [PATCH] Return value from schedule()
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On Thu, 4 Sep 2008 10:21:11 -0600
Matthew Wilcox <matthew@wil.cx> wrote:

> On Thu, Sep 04, 2008 at 06:14:24PM +0200, Ingo Molnar wrote:
> > > If schedule() returned whether or not it had scheduled another
> > > task, we could do something like:
> > > 
> > > 		if (!schedule())
> > > 			udelay(10);
> > 
> > hm, i'm not really sure - this really just seems to be a higher
> > prio variant of yield() combined with some weird code. Do we really
> > want to promote such arguably broken behavior? If there's any
> > chance of any polling to take a material amount of CPU time it
> > should be event driven to begin with.
> 
> Oh, I'm not concerned about CPU utilisation, I'm concerned about PCI
> bus utilisation.  Perhaps I'd like a yield_timeout() function instead
> where I say that I'd like to not run for at least 10 microseconds?
> 
> Can we do that, or are we still jiffie-based there?
> 

use schedule_hrtimerout() for this (hopefully will be in 2.6.28);
see this weeks LWN for an article describing it