Re: [PATCH] Use uname not sysctl to get the kernel revision

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> We will need an implementation that will fall back to sys_sysctl for older
> kernels. This is already common practice in glibc. I don't really
> understand the performance concern because it seems to me that
> _is_smp_system() is only called once per process.
> 
> But isn't this the kind of thing that the Aux Vector is for? I like vDSO
> too, but I think it is best deployed for information of a more dynamic
> nature and performance sensitive.

For a simple "is_smp" kind of flag, I would tend to agree with the
above... for more complex NUMA topology and/or cache characteristics,
which is quite a bigger amount of information, I'm not sure it's worth
copying all of that data on every process exec (and making the initial
AT_ parsing slower). Especially since very few processes actually care
about those.

Ben.