Re: sched_setaffinity usability

[Davide Libenzi]

On Thu, 18 Mar 2004, Ingo Molnar wrote:

> But how about the original issue Ulrich raised: how does user-space
> figure out the NR_CPUS value supported by the kernel? (not the current #
> of CPUs, that can be figured out using /proc/cpuinfo)

Why not a /proc/something? I mean, doesn't glibc already have to handle in 
some way kernels not exporting certain information (in the same way it 
does for missing VDSO)?


> Right now the VDSO mostly contains code and exception-handling data, but
> it could contain real, userspace-visible data just as much: info that is
> only known during the kernel build. There's basically no cost in adding
> more fields to the VDSO, and it seems to be superior to any of the other
> approaches. Is there any reason not to do it?

With /proc/something you can have a single piece of code for all archs 
that exports NR_CPUS. The VDSO should be added to all missing archs. IMO 
performance is not an issue in getting NR_CPUS from userspace.


- Davide


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