Re: [PATCH v3 1/5] perf_event: introduce 'inject' event and get HZ

Ingo Molnar
2009-12-30T09:44:35Z

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, 2009-12-30 at 10:28 +0100, Ingo Molnar wrote:
> > * Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > > On Tue, 2009-12-29 at 13:21 +0800, Xiao Guangrong wrote:
> > > > 'inject' event is a very useful feature and it's suggested by Ingo
> > > > [ See http://lkml.org/lkml/2009/12/28/31 ]
> > >
> > > I really dislike the name, event injection to me would be like a write()
> > > interface where you provide the actual event data to be stuffed in the
> > > output stream.
> > >
> > > This just seems like a very weird way of getting data out. A kind of like
> > > sysconf() but done very strange.
> >
> > What kind of API would you suggest?
>
> sysconf() seems ideal for getting single, mostly constant variables out
> of the kernel, we already have non POSIX (read Linux specific) names in
> there.
>
> _SC_KERNEL_RELOCATION_OFFSET
> _SC_KERNEL_HZ
>
> or somethings like that comes to mind.

Nah. HZ might be static here but we'll have more dynamic parameters so the
sysconf API is rather inflexible there.

I was thinking of something that fits into existing perf API schemes, to keep
it simple and self-sufficient, and to allow for extensions/etc.

Ingo