linux-kernel - Re: [PATCH] [keys] Always use key

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Message-ID: <Pine.LNX.4.64.0803201639590.30696@peripatetic.hades>
Date:	Thu, 20 Mar 2008 16:43:13 +0530 (IST)
From:	Arun Raghavan <arunsr@....iitk.ac.in>
To:	David Howells <dhowells@...hat.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [keys] Always use key_get() to increment key refcount

On Wed, 19 Mar 2008, David Howells wrote:

> Arun Raghavan <arunsr@....iitk.ac.in> wrote:
> 
> > Patch to use key_get() wherever the keys code manually increments the
> > key refcount.
> > 
> > This should make debugging a little simpler for clients, since it
> > becomes easier to track where a key's refcount changes.
> 
> The problem with this is that key_get() is not simply an atomic_inc().  You
> end up introducing an extra conditional into each of these places where one is
> not required.  Now it's possible that the compiler's optimiser is sufficiently
> clever to get rid of them all, but do you guarantee that?

Is this really a significant performance penalty? If yes, wouldn't a
likely() be sufficient to mitigate the penalty?

The same arguments should also be applied to key_put(), I guess.

Regards,
Arun
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