Re: [Starpu-devel] Strange behaviour using GPUs

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

Thanks Nathalie,

I'll try this when I'll happen to be scheduled on a GPU node... (plafrim 
scheduler is quite strange today...)

XL.

Le 9 juil. 2013 à 14:38, Nathalie Furmento a écrit :

> Xavier,
> 
> There was indeed a bug in 1.1.0rc1 which made dmda queues LIFOs . This has 
> been fixed in the branch. We actually found out by seeing MAGMA 
> performances dropping down.
> 
> Could you please try and let us know if that also fixes your problem? I am 
> planning to release 1.1.0rc2 tomorrow, but you could also try by checking 
> out the svn repository.
> 
> Thanks,
> 
> Nathalie
> 
> in On 09/07/2013 14:19, Xavier Lacoste wrote:
>> Hello,
>> 
>> I tried to compare ParSEC and StarPU using full machines (mirage) on 
>> PaStiX.
>> We achieve to have good scaling with ParSEC by statically scheduling task 
>> on GPUs.
>> So, I tried to reproduce the same scheduling with StarPU 1.1.0rc1 and 
>> obtained strange behavious.
>> My GPUs take all there time FetchingInput and PushingOutputs.
>> 
>> The output trace can be seen here : 
>> http://img401.imageshack.us/img401/5213/1pb.png
>> Or, on plafrim cluster :
>> 9 CPUs + 3 GPUs
>> /lustre/lacoste/rsync/log_mirage_AUDI_dmda+LLT+flop+cmin20+frat8+distFlop+selfCopy+fxt_9_3_4231_20130709_120332_crit2_0.5GPUmem.trace
>> 10 + 2 :
>> /lustre/lacoste/rsync/log_mirage_AUDI_dmda+LLT+flop+cmin20+frat8+distFlop+selfCopy+fxt_10_2_4231_20130709_120332_crit2_0.5GPUmem.trace
>> 11 + 1 :
>> /lustre/lacoste/rsync/log_mirage_AUDI_dmda+LLT+flop+cmin20+frat8+distFlop+selfCopy+fxt_11_1_4231_20130709_120332_crit2_0.5GPUmem.trace
>> 12 + 0 :
>> /lustre/lacoste/rsync/log_mirage_AUDI_dmda+LLT+flop+cmin20+frat8+distFlop+selfCopy+fxt_12_0_4231_20130709_120332_crit2_0.5GPUmem.trace
>> 
>> The results are good with 12 CPUs + 0, adding 1 or 2 GPUs bring no loss, 
>> but no gain either, adding three slows down the run time by a factor 10.
>> 
>> Do you have any idea of what can explain this behaviour ?
>> 
>> With a dynamic scheduling, GPUs are usefull with a small number of CPUs 
>> but not with the whole machine.
>> (My cost model may not be accurate enough for the moment... 
>> http://img515.imageshack.us/img515/2348/njz.png)
>> 
>> Thanks,
>> 
>> XL.
>> _______________________________________________
>> Starpu-devel mailing list
>> Starpu-devel@lists.gforge.inria.fr
>> http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/starpu-devel
>