Re: [PATCH 09/11] sched: export task_prio to GPL modules

Mathieu Desnoyers
2011-12-01T22:15:04Z

* Peter Zijlstra (peterz@infradead.org) wrote:
> On Thu, 2011-12-01 at 17:04 -0500, Mathieu Desnoyers wrote:
> > * Peter Zijlstra (peterz@infradead.org) wrote:
> > > On Thu, 2011-12-01 at 16:41 -0500, Mathieu Desnoyers wrote:
> > > > LTTng needs this symbol to prepend the current task dynamic priority
> > > > value to events (optional context information).
> > >
> > > I absolutely detest exporting such stuff. It propagates the idea that
> > > task prio actually means something. Also, modules really shouldn't care.
> >
> > People debugging their SCHED_FIFO/SCHED_RR applications, as well as
> > users of priority-inheritance futexes, may happen to find this
> > information extremely useful.
> >
> > Just saying...
>
> Right until the moment we go do deadlines.. Anyway, it still doesn't
> make sense, your sched_switch() tracepoint handler gets this
> information, why do you need this export at all?

If you don't want to trace sched_switch, but just conveniently prepend
this information to all your events, then lttng lets you dynamically
target this extra bit of information. Note that it's not a mandatory
event field: I call those "context" fields that the tracer prepends to
events, as requested by the user.

Thanks,

Mathieu

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.