From: Axel Kohlmeyer (akohlmey_at_gmail.com)
Date: Mon Jun 06 2011 - 06:57:35 CDT
On Mon, Jun 6, 2011 at 7:49 AM, Norman Geist
<norman.geist_at_uni-greifswald.de> wrote:
> Axel, sure I tested my configuration before telling the world. My results
> are very similar to others I found, so let's say my machine is well
> configured. This machine had a dual core processor since I upgraded to a six
> core a few days ago. Before that, the utilisation with both cores was about
> 6%. Don't say this is expectable, because the same gpu runs at 100% with 1
> core at acemd. Theres much capacity on the tesla for namd.
norman,
those are very unusual numbers. somehow you are running a
configuration that spends _very_ little time in the non-bonded
kernel and thus the GPU is not utilized a lot. thus what you
are seeing is mostly the speedup in the non-accelerated part
of NAMD.
for a single task you should see at least see 20% utilization.
what is the speedup that you get for your system when using
a single NAMD task when going from running on the CPU only
to using the GPU?
> The result of the processor change from 2 to 6 was a expectable three times
> faster execution and a three time higher utilisation of the gpu (now near
> 20%). All my tests with increasing numbers of cores (also with the dual
> core) that share a gpu are always three times faster than the cpus alone. 6
the GPU utilization number printed by nvidia-smi is not capturing
the entire performance of the machine, same as the top command
is not a good benchmarking tool.
> cores with 1 Tesla C2050 is the same as 6 cores with 2 Tesla C2050 and every
> core I add, results in speedup. So I could, if I had, add more cores to see
> what happens and when the limit is reached somewhere. But until now, there's
> no bottleneck in pcie bandwidth or gpu utilisation with namd.
i disagree. you are for some unknown reason not moving a lot of work to the GPU.
this doesn't hold for the general use of GPUs with NAMD.
axel.
> The graph shows the monitoring before and after the cpu change with namd and
> a 1.3 million atoms system.
>
> Norman Geist.
>
>
> -----Ursprüngliche Nachricht-----
> Von: Axel Kohlmeyer [mailto:akohlmey_at_gmail.com]
> Gesendet: Montag, 6. Juni 2011 13:30
> An: Norman Geist
> Cc: Namd Mailing List
> Betreff: Re: namd-l: AMD-PhenomII-1075_GTX470 NAMD-CUDA performance
>
> On Mon, Jun 6, 2011 at 7:11 AM, Norman Geist
> <norman.geist_at_uni-greifswald.de> wrote:
>> Dear Axel,
>>
>> What I tried to say was that one thing is of course the bandwidth of the
>> pcie bus. But what's about the utilization of the gpu? If I have a
>> configuration of oversubscription that would still allow communication
>> between cpu and gpu due to enough pcie bandwidth, that wouldn't help me if
>> my gpu is already fully utilized. And that’s what I tried to say. I ran a
>> 1,3 million atoms system on a tesla C2050, shared by 6 cpu cores, the
>> utilization of the gpu is about 20 percent. I haven't worked with the
>
> i wouldn't be surprised to see such a low utilization since
> most of the time is probably spent on moving data in and
> out of the GPU. a 6x oversubscription is pretty extreme.
> the main benefit is probably in the non-GPU accelerated parts
> (which is still a significant amount of work for such a large system).
>
> have you made a systematic test in running different number
> of host processes?
>
> please note that high-end GeForce cards can have as many
> or even more (GTX 580!) cores than a C2050.
>
> the huge difference in cost between the Tesla and the GeForce
> does not automatically translate into different performance for
> a code that doesn't benefit from the features of the Tesla
> (4x double precision units, more memory, ECC memory,
> more reliability). in fact, turning on the ECC of the Tesla may
> even slow it down.
>
> axel.
>
>> geforce cards yet, but I can imagine that the utilization of the gpu would
>> be much higher here because of the less cuda cores, what means that
> further
>> cpu cores wouldn't help here, while they would with the tesla C2050. Maybe
>> my post was too general and not enough directed to namd, sorry for this.
>>
>> Norman Geist.
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Axel Kohlmeyer [mailto:akohlmey_at_gmail.com]
>> Gesendet: Montag, 6. Juni 2011 12:50
>> An: Norman Geist
>> Cc: Francesco Pietra; Namd Mailing List
>> Betreff: Re: namd-l: AMD-PhenomII-1075_GTX470 NAMD-CUDA performance
>>
>> On Mon, Jun 6, 2011 at 5:51 AM, Norman Geist
>> <norman.geist_at_uni-greifswald.de> wrote:
>>> Hi Francesco,
>>>
>>> As your output shows, both gtx cards were in use.
>>>
>>> Pe 1 sharing CUDA device 1 -> This is gtx 1
>>> Pe 0 sharing CUDA device 0 -> This is gtx 2
>>>
>>> The driver you get from nvidia and from your os is the same I think. The
>> nvidia driver must be compiled for your platform, the os driver already
> is.
>>>
>>> If more gpus bring better performance regards heavily on your hardware
> and
>> system size. Just try if 6 cpus sharing on gtx is slower or the same as
>> 6cpus sharing 2 gtx cards. I think the oversubscription of such a gtx is
>> limited very quick and u should get better performance while using both
> the
>> cards.
>>
>> of course, oversubscribing GPUs can only help up to a point. it doesn't
>> create more GPUs, it only allows you to use it more efficiently. think of
>> it like hyperthreading. that also it a trick to improve utilization of
>> the different
>> units on the CPU, but it cannot replace a full processor core and its
>> efficiency
>> is limited to how much the different units of the CPU are occupied and
>> by the available memory bandwidth.
>>
>>>Not so if using a Tesla C2050. This card can be shared by more than 6
> cores
>> without running into a bottleneck if plugged into a pcie 2.0 x16 slot.
>>
>> this is nonsense. as far as the CUDA code in NAMD is concerned there is
> not
>> much of a difference between a Tesla and a GeForce card. In fact the
>> high-end
>> GeForce cards are often faster due to having higher memory and processor
>> clocks.
>> there is, however, the bottleneck of having sufficient PCI-e bus
>> bandwidth available,
>> but that affects both type of cards.
>>
>> axel.
>>
>>> Best regards.
>>>
>>> Norman Geist.
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: owner-namd-l_at_ks.uiuc.edu [mailto:owner-namd-l_at_ks.uiuc.edu] Im
> Auftrag
>> von Francesco Pietra
>>> Gesendet: Montag, 6. Juni 2011 11:16
>>> An: NAMD
>>> Betreff: Fwd: namd-l: AMD-PhenomII-1075_GTX470 NAMD-CUDA performance
>>>
>>> I forgot to show the output log:
>>>
>>> Charm++> scheduler running in netpoll mode.
>>> Charm++> Running on 1 unique compute nodes (6-way SMP).
>>> Charm++> cpu topology info is gathered in 0.000 seconds.
>>> Info: NAMD CVS-2011-06-04 for Linux-x86_64-CUDA
>>>
>>> Info: Based on Charm++/Converse 60303 for net-linux-x86_64-iccstatic
>>> Info: Built Sat Jun 4 02:22:51 CDT 2011 by jim on lisboa.ks.uiuc.edu
>>> Info: 1 NAMD CVS-2011-06-04 Linux-x86_64-CUDA 6 gig64 francesco
>>> Info: Running on 6 processors, 6 nodes, 1 physical nodes.
>>> Info: CPU topology information available.
>>> Info: Charm++/Converse parallel runtime startup completed at 0.00653386 s
>>> Pe 3 sharing CUDA device 1 first 1 next 5
>>> Pe 3 physical rank 3 binding to CUDA device 1 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Pe 1 sharing CUDA device 1 first 1 next 3
>>> Pe 1 physical rank 1 binding to CUDA device 1 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Pe 5 sharing CUDA device 1 first 1 next 1
>>> Did not find +devices i,j,k,... argument, using all
>>> Pe 5 physical rank 5 binding to CUDA device 1 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Pe 0 sharing CUDA device 0 first 0 next 2
>>> Pe 0 physical rank 0 binding to CUDA device 0 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Pe 2 sharing CUDA device 0 first 0 next 4
>>> Pe 2 physical rank 2 binding to CUDA device 0 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Pe 4 sharing CUDA device 0 first 0 next 0
>>> Pe 4 physical rank 4 binding to CUDA device 0 on gig64: 'GeForce GTX
>>> 470' Mem: 1279MB Rev: 2.0
>>> Info: 1.64104 MB of memory in use based on CmiMemoryUsage
>>>
>>>
>>>
>>>
>>> ---------- Forwarded message ----------
>>> From: Francesco Pietra <chiendarret_at_gmail.com>
>>> Date: Mon, Jun 6, 2011 at 9:54 AM
>>> Subject: namd-l: AMD-PhenomII-1075_GTX470 NAMD-CUDA performance
>>> To: NAMD <namd-l_at_ks.uiuc.edu>
>>>
>>>
>>> Hello:
>>>
>>> I have assembled a gaming machine with
>>>
>>> Gigabyte GA890FXA-UD5
>>> AMD PhenomII 1075T (3.0 GHz)
>>> 2xGTX-470
>>> AMD Edition 1280MB GDDRV DX11 DUAL DVI / MINI HDMI SLI ATX
>>> 2x 1TB HD software RAID1
>>> 16 GB RAM DDR3 1600 MHz
>>> Debian amd64 whyzee
>>> NAMD_CVS-2011-06-04_Linux-x86_64-CUDA.tar.gz
>>> No X server (ssh to machines with X server)
>>>
>>> In my .bashrc:
>>>
>>> NAMD_HOME=/usr/local/namd-cuda_4Jun2010nb
>>> PATH=$PATH:$NAMD_HOME/bin/namd2; export NAMD_HOME PATH
>>> PATH="/usr/local/namd-cuda_4Jun2010nb/bin:$PATH"; export PATH
>>>
>>> if [ "LD_LIBRARY_PATH" ]; then
>>> export
>> LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/namd-cuda_4Jun2010nb
>>> else
>>> export LD_LIBRARY_PATH="/usr/local/namd-cuda_4Jun2010nb"
>>>
>>>
>>> I lauched a RAMD rrn on a >200,000-atoms system with
>>>
>>> charmrun $NAMD_HOME/bin/namd2 ++local +p6 +idepoll ++verbose
>>> filename.conf 2>&1 | tee filename.log
>>>
>>> It runs fine, approximately (by judging from "The last velocity output
>>> at each ten-steps writing) ten times faster than a 8-CPU shared-mem
>>> machine with dual-opteron 2.2 GHz.
>>>
>>> I did nothing as to indicating the GTX-470 to use. Can both be used?
>>> Is that the same (in terms of performance) using the nvidia-provided
>>> cuda driver or the one available with the OS (Debian)?. Sorry for the
>>> last two naive questions, perhaps resulting from the stress of the
>>> enterprise. I assume that "nvidia-smi" is of no use for these graphic
>>> cards.
>>>
>>> Thanks a lot for advice
>>>
>>> francesco pietra
>>>
>>>
>>>
>>
>>
>>
>> --
>> Dr. Axel Kohlmeyer
>> akohlmey_at_gmail.com http://goo.gl/1wk0
>>
>> Institute for Computational Molecular Science
>> Temple University, Philadelphia PA, USA.
>>
>>
>
>
>
> --
> Dr. Axel Kohlmeyer
> akohlmey_at_gmail.com http://goo.gl/1wk0
>
> Institute for Computational Molecular Science
> Temple University, Philadelphia PA, USA.
>
-- Dr. Axel Kohlmeyer akohlmey_at_gmail.com http://goo.gl/1wk0 Institute for Computational Molecular Science Temple University, Philadelphia PA, USA.
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