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SubjectRe: [perfmon] Re: [perfmon2] perfmon2 merge news
> Yes, horribly more complicated because of locking issues within perfmon.
> As soon as you expose a file descriptor, you need some locking to prevent
> multiple user threads (malicious or not) to compete to access the PMU state.

Why do you need the file descriptor?

One of the main problems with perfmon is the complicated user interface.

Naively I would assume just some thread global state should be sufficient.

> I think the value add of NMI can be as well achieved with advanced PMU features
> such as Intel Core 2 PEBS.

True probably, although only on CPUs that support PEBS. Dropping features
for old CPUs is unfortunately quite difficult in Linux, and in this case
probably not an option because there are so many of them (e.g. all of AMD
not Fam10h)

-Andi
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