Re: [Starpu-devel] reducing STARPU_OPENCL_PIPELINE to 0

[Samuel Thibault <samuel.thibault@inria.fr>]

Hello,

(trying to catch up after my vacancies)

Jeff Hand, le Thu 04 Jun 2015 11:25:21 -0500, a écrit :
> ================================================================
> [starpu][_starpu_opencl_driver_init] Warning: reducing 
> STARPU_OPENCL_PIPELINE
> to 0 because blocking drivers are not enabled (and simgrid is not enabled)
> ================================================================

Oops, the message is bogus: it complains because blocking drivers are
enabled, which prevents from pipelining tasks (which can not be done
without blocking drivers).

> According to "backport r12085 from trunk: Advise the user to use
> --enable-blocking-drivers to avoid consuming real CPU for virtual CPU 
> idling" 
> my assumption is "--enable-blocking-drivers" is preferred.

This commit is about simgrid mode only, not about non-simgrid mode.

> As a test, I removed the code setting the pipeline to 0.  The performance
> seemed to be about the same.  The StarPU tests passed and my tests passed 
> with
> the modification.

I'd say it's just by luck that it happens to be actually working :)
It'll however actually be running one task at a time, i.e. just as if
STARPU_OPENCL_PIPELINE was set to 0.

Samuel