Re: [Starpu-devel] Performance decreasing by adding empty tasks

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Samuel Thibault, le Mon 13 Feb 2012 15:46:21 +0100, a écrit :
> Xavier Lacoste, le Wed 08 Feb 2012 15:26:40 +0100, a écrit :
> > Do you have any clue ?
> 
> Not really. We'd need to know why
> 
> > I also noticed on all my Gantt diagramms (even with the best ones) that
> > I have one task isolated, a large amount of "blocked" time and then my 
> > task
> > (I can send Gantts)
> 
> that ↑ happens. You can for instance try to create a DAG (section
> "Performance feedback", "Off-line performance feedback" of the
> documentation). Perhaps your use of StarPU implies a lot of useless
> dependencies between tasks.

Also, do your empty tasks have a performance model? In such case the
scheduler tries to switch to a greedy strategy, which might get wrong.

In any case we need to get a closer look on your application, to check
what happens in the scheduler in your case.

Samuel