Messages in this thread | | | Subject | Re: [PATCH] Resurrect old pr_debug() semantics as pr_devel() | From | Michael Ellerman <> | Date | Tue, 07 Apr 2009 12:08:47 +1000 |
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On Mon, 2009-04-06 at 17:24 -0400, Jason Baron wrote: > On Mon, Apr 06, 2009 at 02:30:03PM +1000, Michael Ellerman wrote: > > pr_debug() used to produce zero code unless DEBUG was #defined. This is > > now no longer the case in practice[1]. > > > > There are places where it's useful to have debugging printks, but we > > don't want them to generate any code in production kernels. > > > > So add a new macro, pr_devel(), for _devel_opment, to provide the old > > semantics, ie. if the programmer doesn't explicitly enable debugging, > > no code is produced. > > > > [1]: You can turn CONFIG_DYNAMIC_DEBUG off, but it's enabled in at least > > one distro kernel, so it's not really a solution. > > > > hmm...its designed to have low overhead when CONFIG_DYNAMIC_DEBUG > is on, but none of the debugging printks are enabled.
Sure, it does that fairly well, and there are places where it's a good trade off to have the debug available at the cost of a bit more code.
> Is there a specific benchmark or test case that is unaccpetable?
Yes. Compiling with DYNAMIC_DEBUG=y generates a non-zero amount of code for each pr_debug(), and in some places that is unacceptable. :)
cheers
-- Michael Ellerman OzLabs, IBM Australia Development Lab
wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183)
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