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

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Message-ID: <20080904162111.GM2772@parisc-linux.org>
Date:	Thu, 4 Sep 2008 10:21:11 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	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, 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?

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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