linux-kernel - Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based on semi-formal proof"

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Message-ID: <20110525071816.GG429@elte.hu>
Date:	Wed, 25 May 2011 09:18:16 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	mingo@...hat.com, hpa@...or.com, tglx@...utronix.de
Subject: Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based
 on semi-formal proof"


* Yinghai Lu <yinghai@...nel.org> wrote:

> >> got:
> >>
> >> [   32.803704] cpu_dev_init done
> >> [   99.171292] memory_dev_init done
> > 
> > So the difference between these two is noise, I hope.  Adding a static
> > inline function that is not used should not have an effect on performance.
> > Still, the difference between 6 seconds and 60 seconds rises far above
> > this noise level, so the big differences are likely quite real.
> 
> could be softirq to kthread change...

Softirq processing can be pretty nondeterministic (for example there's no 
guarantee that we process all softirqs) - but kthreads ought to be pretty 
deterministic. Weird.

Thanks,

	Ingo
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