linux-kernel - Re: [PATCH 00/10] jump label: introduce very

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Message-ID: <20120222073251.GB17291@elte.hu>
Date:	Wed, 22 Feb 2012 08:32:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jason Baron <jbaron@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	a.p.zijlstra@...llo.nl, mathieu.desnoyers@...icios.com,
	davem@...emloft.net, ddaney.cavm@...il.com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups +
 docs


* Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 2012-02-21 at 15:20 -0500, Jason Baron wrote:
> 
> > I'm not really too hung up on the naming, but I did think 
> > that very_[un]likely were an interesting possibility.
> 
> The problem comes from what Peter said. They are too similar 
> to "likely()" and "unlikely()", and can become confusing.

See my other mail.

> Maybe "static_likely()" and "static_unlikely()" as the word 
> "static" can imply something strange about these. Or perhaps a 
> "const_likely()"?
> 
> Maybe "dynamic_branch_true()" and "dynamic_branch_false()". This may be
> the most descriptive.

too long.

'static branch' or 'static condition' is not a bad concept, if 
people don't find the similarity to 'static' too confusing ;-).

But it is fundamentally mixing execution and *data type* and it 
is not conveying the build time bias properly.

So the best high level naming would be something like:

	struct static_condition static_flag = STATIC_COND_FALSE;


	if (very_unlikely(&static_flag)) {
		...
	}

	...

	static_cond_inc(&static_flag);
	...
	static_cond_dec(&static_flag);


See how *both* the build time bias and the cost of a state 
transition is properly conveyed?

I suggested something like this to Jason in the off-list 
discusion and it's not fully implemented yet. Let me whip up a 
test branch [pun and potential confusion unintended] that shows 
it.

Thanks,

	Ingo
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