Re: [Starpu-devel] GPU issue with r12137

[Xavier Lacoste <xavier.lacoste@inria.fr>]

Indeed, this error is very strange...
Yes I have only one GPU with 11 cores. I can try different configuration if 
you want.


Le 3 avr. 2014 à 14:24, Samuel Thibault <samuel.thibault@ens-lyon.org> a 
écrit :

> Xavier Lacoste, le Thu 03 Apr 2014 13:44:00 +0200, a écrit :
>> I runned the test several time because i didn't believe this can be the
>> cause....
>> 
>> Indeed doing :
>> 
>> diff --git a/src/datawizard/coherency.c b/src/datawizard/coherency.c
>> index 6e67156..8e82163 100644
>> --- a/src/datawizard/coherency.c
>> +++ b/src/datawizard/coherency.c
>> @@ -172,13 +172,13 @@ static int worker_supports_direct_access(unsigned 
>> node,
>> unsigned handling_node)
>>                        enum starpu_node_kind kind = starpu_node_get_kind
>> (handling_node);
>>                        /* GPUs not always allow direct remote access: if 
>> CUDA4
>>                         * is enabled, we allow two CUDA devices to
>> communicate. */
>> -                       return
>> -#if 0
>> +                       return kind ==
>> +#if 1
>>                                /* CUDA does not seem very safe with 
>> concurrent
>>                                 * transfer queueing, avoid queueing from 
>> CPUs
>> */
>> -                               kind == STARPU_CPU_RAM ||
>> +                               STARPU_CPU_RAM ||
>> #endif
>> -                               kind == STARPU_CUDA_RAM;
>> +                               STARPU_CUDA_RAM;
>>                }
>> #else
>>                        /* Direct GPU-GPU transfers are not allowed in 
>> general
>> */
>> 
>> solves the issue.
> 
> Uh?!
> 
> Since kind can not be both STARPU_CPU_RAM || STARPU_CUDA_RAM, it
> basically means always returning 0.  What is really disturbing is that
> all it does is disabling GPU-GPU direct transfers.  You are testing with
> just one GPU, aren't you?
> 
> Samuel