linux-kernel - Re: [PATCH] Return value from schedule()

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Message-ID: <20080904103049.01f748d9@infradead.org>
Date:	Thu, 4 Sep 2008 10:30:49 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...l.org>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-pci@...r.kernel.org,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: [PATCH] Return value from schedule()

On Thu, 4 Sep 2008 10:21:11 -0600
Matthew Wilcox <matthew@....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
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