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SubjectRe: [RFC 0/3] Basic support for LWP

* Hans Rosenfeld <hans.rosenfeld@amd.com> wrote:

> But thats not required to use LWP instructions. Maybe Robert will add
> it to perf some day, or maybe not. It is completely optional, and how
> it is implemented at some point in the future is completely irrelevant
> to the basic support of LWP.

It isnt irrelevant. If the concept is implemented in a crappy way, if
there are random user-space libraries that do not properly expose these
capabilities and do not allow them to extend existing perf functionality
in a natural way then we might be better off not adding overhead to the
scheduler and not enabling it at all.

So thoughts need to be made what the point of it all is and how it
integrates into perf. If it doesnt integrate, if the whole plan is to
just get it to user-space where it can be messed up freely in some CPU
specific way then color me thoroughly uninterested. We have a generic
instrumentation framework for a reason.

We very much want to know the structure of that area and want to make
use of it not just on a per task basis. We also want to expose it all in
a more generalized form.

I cannot believe something like this was committed into silicon without
at minimum talking to people who have a clue about where it will (and
should) all go ...

Ingo


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