Re: [PATCH] cputopology: Always define CPU topology information [4th try]

From: Ben Hutchings
Date: Wed Jul 16 2008 - 19:11:20 EST

Nathan Lynch wrote:
> Hi Ben-
> Ben Hutchings wrote:
> > Not all architectures and configurations define CPU topology information.
> > This can result in an empty topology directory in sysfs, and requires
> > in-kernel users to protect all uses with #ifdef - see
> > <>.
> >
> > The documentation of CPU topology specifies what the defaults should be
> > if only partial information is available from the hardware. So we can
> > provide these defaults as a fallback.
> I've been looking at adding topology information to powerpc and I came
> across this.
> I understand the need for fallback definitions of the topology APIs
> within the kernel, but I'm not sure I agree with exposing these things
> in sysfs unconditionally -- the default values for physical_package_id
> and core_id don't really make sense on powerpc (and other non-x86
> architectures, I suspect).

In what way are they wrong?

> Would you object to a patch which exposes in sysfs only the topology
> information which the architecture provides?

I was primarily concerned with having the fallbacks available in-kernel.
However, I don't think you will be doing user-space any favours by
requiring checks for missing attributes for ever.


Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
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