linux-kernel - Re: Network slowdown due to CFS

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Message-ID: <20071001170903.GA2492@elte.hu>
Date:	Mon, 1 Oct 2007 19:09:03 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	Jarek Poplawski <jarkao2@...pl>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	David Schwartz <davids@...master.com>,
	linux-kernel@...r.kernel.org, Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Martin Michlmayr <tbm@...ius.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: Network slowdown due to CFS


* Chris Friesen <cfriesen@...tel.com> wrote:

> Ingo Molnar wrote:
> 
> >But, because you assert it that it's risky to "criticise sched_yield() 
> >too much", you sure must know at least one real example where it's right 
> >to use it (and cite the line and code where it's used, with 
> >specificity)?
> 
> It's fine to criticise sched_yield().  I agree that new apps should 
> generally be written to use proper completion mechanisms or to wait 
> for specific events.

yes.

> However, there are closed-source and/or frozen-source apps where it's 
> not practical to rewrite or rebuild the app.  Does it make sense to 
> break the behaviour of all of these?

See the background and answers to that in:

   http://lkml.org/lkml/2007/9/19/357
   http://lkml.org/lkml/2007/9/19/328

there's plenty of recourse possible to all possible kinds of apps. Tune 
the sysctl flag in one direction or another, depending on which behavior 
the app is expecting.

	Ingo
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