On Fri, 24 Aug 2018, Peter Zijlstra wrote:
> > +++ b/include/uapi/linux/perf_event.h
> > @@ -143,6 +143,8 @@ enum perf_event_sample_format {
> > PERF_SAMPLE_PHYS_ADDR = 1U << 19,
> >
> > PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */
> > +
> > + __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63,
> > };
> >
>
> Hurphm.. visible yes, but as you say, also quite useless. Does it really
> make sense to document that?
Well, it should probably be documented either in the manpage or else in
perf_event.h (even if it's just "internal use, don't use") as we can't
really expect people to download a git tree and do a git-blame to try to
figure out what this mysterious field is all about.
Also, this change increased the size of the enum from 32 to 64 bits on
32-bit machines, though that only really matters if the user is doing
something really weird with enum variables.
Vince
