[ltt-dev] [patch] add tracepoints to trace activate/deactivate task

[peterz@infradead.org (Peter Zijlstra)]

On Mon, 2008-12-08 at 17:38 -0500, Jason Baron wrote:
> On Mon, Dec 08, 2008 at 08:54:10PM +0100, Peter Zijlstra wrote:
> > On Mon, 2008-12-08 at 14:49 -0500, Jason Baron wrote:
> > > hi,
> > > 
> > > I thought it would be useful to track when a task is
> > > 'activated/deactivated'. This case is different from wakeup/wait, in that
> > > task can be activated and deactivated, when the scheduler re-balances
> > > tasks, the allowable cpuset changes, or cpu hotplug occurs. Using these
> > > patches I can more precisely figure out when a task becomes runnable and
> > > why. 
> > 
> > Then I still not agree with it because it does not expose the event that
> > did the change.
> > 
> > If you want the cpu allowed mask, put a tracepoint there. If you want
> > migrate information (didn't we have that?) then put one there, etc.
> > 
> 
> well, with stap backtrace I can figure out the event, otherwise i'm
> sprinkling 14 more trace events in the scheduler...I can go down that
> patch if people think its better?

what events are you interested in? some of them are just straight
syscall things like nice.

But yes, I'd rather you'd do the events - that's what tracepoints are
all about, marking indivudual events, not some fugly hook for stap.