vsdo_datapage.h WTF?

[Nathan Lynch]

Benjamin Herrenschmidt wrote:
> On Sun, 2006-10-08 at 00:58 +1000, Anton Blanchard wrote:
> > Hi,
> > 
> > > No. There -used- to be this systemcfg structure that was exposed to
> > > userspace on ppc64. I made it deprecated. However, for the sake of
> > > backward compatbility, I kept vdso datapage with the exact same layout
> > > for the first part of it (before the syscall maps) and haven't removed
> > > the mmap call for it, but it will be gone soon.
> > 
> > We need a way to export cache size/associativity information (sysfs,
> > /proc/device-tree parsing?) and a plan to fix the applications using it
> > first.
> 
> The application using it can still use its own copy of the old header
> tho. And that's why I haven't removed the /proc file and will probably
> not do in the near future.
> 
> Regarding cache infos, I noticed the lack of anything useful in the
> device-tree on Power5 LPAR or did I miss something ? Which means that on
> recent machines, the kernel doesn't even know.

On shared-processor partitions device nodes for caches are not
provided at all.  In dedicated mode the caches can be correlated to
their respective processors by looking at the "l2-cache" properties
iirc.