[ltt-dev] LTTV Enhancement

Mathieu Desnoyers mathieu.desnoyers at polymtl.ca
Fri Nov 27 12:26:14 EST 2009

* Pierre-Marc Fournier (pierre-marc.fournier at polymtl.ca) wrote:
> Mathieu Desnoyers wrote:
> > * Chris Smowton (cs448 at cam.ac.uk) wrote:
> >> Hey,
> >>
> >> Here's a slightly more constructive patch: this one adds support in
> >> LTTV's generic state monitoring code and its control flow visualiser to
> >> note when a process is woken by another process using the
> >> sched_try_wakeup event.
> >>
> >> Previously the woken process would continue to register its old state
> >> until such time as it got scheduled; here the process transitions to
> >> WAIT_CPU state (like preempted processes, indicating it is ready to run
> >> but not currently scheduled). Ordinarily we see this state exist very
> >> briefly, in between the device driver IRQ (typically) clearing it to run
> >> and the scheduler invocation after irq_exit, but on a heavily loaded
> >> system we might see a large stripe of dark yellow indicating the process
> >> is ready but cannot yet be allocated a core.
> >>
> > 
> > This is indeed the right thing to do ! :) Thanks very much for the
> > patch.
> > 
> > I'll wait for feedback from Pierre-Marc, who maintains the resource
> > view, to see if this view too need to be updated. When I get his OK,
> > I'll pull your patch.
> > 
> This looks like an excellent idea. You have my OK.
> pmf

Yep, I looked at it, and it seems good. I did a bit of coding-style
modification to the new sched_try_wakeup() function and merged the

I think we should probably also deal with the sched wakeup_new_task
event, shouldn't we ? (a patch to support this would be welcome)



Mathieu Desnoyers
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