Re: [RFC] Splitting out kernel<=>userspace ABI headers

[H. Peter Anvin]

Followup to:  <76E84FF2-A76E-4114-8E80-E07E6A497C7D@xxxxxxx>
By author:    Kyle Moffett <mrmacman_g4@xxxxxxx>
In newsgroup: linux.dev.kernel
> 
> The kernel already needs those same optimized routines for its own
> operation (EX: all the ASM alternative() statements).  Since userspace
> wants some of those as well, it would make sense to share them between
> kernel and userspace and reduce the number of libraries you would need
> to optimize when adding a new arch.  I don't think that we should add
> optimized assembly for things that _aren't_ needed in the kernel, but
> it should share what code it does have.
> 
> A side benefit of the vDSO method is that you would be able to take a
> standard distro install and have the kernel automatically select the
> correct vDSO image at runtime, simultaneously optimizing itself and
> chunks of userspace.
> 

First of all, a lot of these are inlines, and they derive a chunk of
their benefit from being inline.  Second, even if bundled with the
kernel, which I'm not sure is wise, there is no reason they can't just
be turned into libraries.  *Some functions* you're right, can be
optimized this way, but I'm not sure if that justifies compiling them
into the kernel that way.

	-hpa
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