* Peter Zijlstra <[email protected]> wrote:
> > It also allows system-wide profiling after you've modified a
> > library to self-profile, while your suggestion does not
> > allow that.
>
> But its no long self-profiling when some other process is
> involved. And system wide is definitely not self.
If I'm a library developer and want to self-profile my
modifications, then it's entirely appropriate to do a
system-wide profile to see the system-wide use of this library!
System-wide and self-profiling is not exclusive. Think of it as
a narrow, precise filter applied to a given area of
functionality only.
AFAICS the alternative, under your method, would be to recompile
every single app in the system - that's cumbersome beyond
imagination, I wouldn't even call it a solution, let alone a
quality implementation.
> > > It really isn't that hard to make userspace do what is
> > > needed, it just takes a bit of work.
> >
> > Even if your suggested solution was available (it isn't), my
> > suggested approach is easier to use and covers more
> > usecases.
> >
> > User-space expecting the kernel to provide usable and
> > minimal interfaces is not 'being silly'. It's the
> > fundamental task of a kernel to provide them.
>
> Bloating the interface for something that is already well
> possible is.
There's no 'bloat' worth speaking off: a single bit out of an
already allocated bitmap, plus a single check in an already
existing loop, plus a single new command-line flag to the
tooling side and minimal glue.
There's no runtime overhead to any other perf functionality, at
all.
Thanks,
Ingo
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