Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect

[Ingo Molnar <mingo@kernel.org>]

* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Fri, 2012-07-27 at 09:26 +0200, Ingo Molnar wrote:
> > 
> > Maybe someone on Cc: would be interested in implementing this 
> > new perf events feature? 
> 
> Why would we go build new kernel interfaces because userspace 
> is silly?

Because it's (much) easier to use the existing perf tools almost 
as-is instead of librarizing your own.

It would also allow other usecases, like self-profiling a 
library and then profiling it within the context of a larger app 
that you don't want to rebuild and which dynamically links this 
library.

It also allows system-wide profiling after you've modified a 
library to self-profile, while your suggestion does not allow 
that.

> 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.

Thanks,

	Ingo