[gmx-developers] Gromacs with GPU

[Åke Sandgren]

Btw, I mostly see this problem when running gmx tune_pme when the npme
under testing results in there being to few PP processes to utilize all
GPU engines..

On 09/22/2017 01:54 PM, Åke Sandgren wrote:
> Ok, then I'll have to write better instructions for our users.
> 
> On 09/22/2017 01:19 PM, Mark Abraham wrote:
>> Hi,
>>
>> Currently the hwloc support doesn't do much except inspect the hardware
>> and help produce the report in the log file. Obviously it should be used
>> for helping with such placement tasks, and that's why we're adopting it,
>> but nobody has prioritized specializing the task-assignment code yet.
>> For the moment, such things are still up to the user.
>>
>> Mark
>>
>> On Fri, Sep 22, 2017 at 1:10 PM Åke Sandgren <ake.sandgren at hpc2n.umu.se
>> <mailto:ake.sandgren at hpc2n.umu.se>> wrote:
>>
>>     Hi!
>>
>>     I am seeing a possible performance enhancement (possibly) when running
>>     gromacs on nodes with multiple gpu cards.
>>     (And yes I know this is perhaps a mote point since current GPU cards
>>     don't have dual engines per card)
>>
>>     System:
>>     dual socket 14-core broadwell cpus
>>     2 K80 cards, one on each socket.
>>
>>     Gromacs built with hwloc support.
>>
>>     When running a dual node (56 core)
>>
>>     gmx_mpi mdrun -npme 4 -s ion_channel_bench00.tpr -resetstep 20000 -o
>>     bench.trr -x bench.xtc -cpo bench.cpt -c bench.gro -e bench.edr -g
>>     bench.log -ntomp 7 -pin on -dlb yes
>>
>>     job, (slurm + cgroups), gromacs doesn't fully take hwloc info into
>>     account. The job correctly gets allocated on cores, but looking at
>>     nvidia-smi and hwloc-ps i can see that the PP processes are using a
>>     suboptimal selection of GPU engines.
>>
>>     The PP processes are placed one on each CPU socket (according to which
>>     process-ids are using the GPUs and the position of those pids according
>>     to hwloc-ps), but they both uses gpu engines from the same (first)
>>     K80 card.
>>
>>     It would be better to have looked at the hwloc info and selected CUDA
>>     devices 0,2 (or 1,3) instead of 0,1.
>>
>>
>>     Any comments on that?
>>
>>     Attached nvidia-smi + hwloc-ps output
>>
>>     --
>>     Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
>>     Internet: ake at hpc2n.umu.se <mailto:ake at hpc2n.umu.se>   Phone: +46 90
>>     7866134 <tel:090-786%2061%2034> Fax: +46 90-580 14 <tel:090-580%2014>
>>     Mobile: +46 70 7716134 <tel:070-771%2061%2034> WWW:
>>     http://www.hpc2n.umu.se
>>     --
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>>
> 

-- 
Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
Internet: ake at hpc2n.umu.se   Phone: +46 90 7866134 Fax: +46 90-580 14
Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se