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osg apps on gpu cluster


 
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Trajce Nikolov NICK
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PostPosted: Mon Oct 01, 2018 6:43 pm    Post subject:
osg apps on gpu cluster
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Hi Community,


I am totally new to this topic and that is the reason I am pinging you this time. Anyone with some experience or hints? I am after running (Linux) osg app N times so each app to have dedicated GPU, something in this fashion.


I will investigate this too, but any word from you is highly appreciated.


Thanks a bunch as always!


Cheers,
Nick


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trajce nikolov nick

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Chris Hanson
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PostPosted: Mon Oct 01, 2018 7:22 pm    Post subject:
osg apps on gpu cluster
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I think Robert advised me on tweaking this probably 4 years ago for a Windows system with 16 display outputs all running from one EXE, ensuring there were the proper number of contexts and threads all playing nicely so as not to jam up the bus.

What's your hardware profile look like? Which Linux OS? What CPUs and how many, what display cards, and how many, how many outputs, etc. The exact best mechanism may not be invariant across all situations.


On Mon, Oct 1, 2018 at 7:43 PM Trajce Nikolov NICK < (
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Quote:
Hi Community,


I am totally new to this topic and that is the reason I am pinging you this time. Anyone with some experience or hints? I am after running (Linux) osg app N times so each app to have dedicated GPU, something in this fashion.


I will investigate this too, but any word from you is highly appreciated.


Thanks a bunch as always!


Cheers,
Nick


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trajce nikolov nick



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Chris 'Xenon' Hanson, omo sanza lettere. http://www.alphapixel.com/
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Per Nordqvist
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PostPosted: Tue Oct 02, 2018 5:12 am    Post subject:
osg apps on gpu cluster
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Hello Chris, thanks for chipping in.

I and Nick are working to utilize as much of the GPUs as possible, either on single machine or cluster.So hardware is not yet decided, but let's assume ubuntu 16+, multiple modern Nvidia gaming cards, but still single screen.


Cheers
Per



On Mon, 1 Oct 2018, 21:22 Chris Hanson, < (
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Quote:
I think Robert advised me on tweaking this probably 4 years ago for a Windows system with 16 display outputs all running from one EXE, ensuring there were the proper number of contexts and threads all playing nicely so as not to jam up the bus.

What's your hardware profile look like? Which Linux OS? What CPUs and how many, what display cards, and how many, how many outputs, etc. The exact best mechanism may not be invariant across all situations.


On Mon, Oct 1, 2018 at 7:43 PM Trajce Nikolov NICK < (
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)> wrote:

Quote:
Hi Community,


I am totally new to this topic and that is the reason I am pinging you this time. Anyone with some experience or hints? I am after running (Linux) osg app N times so each app to have dedicated GPU, something in this fashion.


I will investigate this too, but any word from you is highly appreciated.


Thanks a bunch as always!


Cheers,
Nick


--
trajce nikolov nick



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--
Chris 'Xenon' Hanson, omo sanza lettere. http://www.alphapixel.com/
Training • Consulting • Contracting
3D • Scene Graphs (Open Scene Graph/OSG) • OpenGL 2 • OpenGL 3 • OpenGL 4 • GLSL • OpenGL ES 1 • OpenGL ES 2 • OpenCL
Legal/IP • Forensics • Imaging • UAVs • GIS • GPS • osgEarth • Terrain • Telemetry • Cryptography • LIDAR • Embedded • Mobile • iPhone/iPad/iOS • Android
@alphapixel facebook.com/alphapixel (775) 623-PIXL [7495]






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robertosfield
OSG Project Lead


Joined: 18 Mar 2009
Posts: 12145

PostPosted: Tue Oct 02, 2018 7:54 am    Post subject:
osg apps on gpu cluster
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Hi Nick & Per,

On Tue, 2 Oct 2018 at 06:12, Per Nordqvist <> wrote:
Quote:
I and Nick are working to utilize as much of the GPUs as possible, either on single machine or cluster.
So hardware is not yet decided, but let's assume ubuntu 16+, multiple modern Nvidia gaming cards, but still single screen.

osgViewer has been written from the ground up to support multiple GPUs
on a single machine with a single application.

The basic concept is the View's master Camera controls the overall
view, and a series of slave Camera's assign to the View handle the
rendering for each graphics card/display. The osgwindow example is
the simplistic example of this in action. A search for addSlave in
the OSG codebase will reveal lots of other examples of it in action -
it can be used for a wide range of tasks.

The OSG out of the box will default to DrawThreadPerContext
ThreadingModel on modern machines, you might find
CullDrawThreadPerContext more appropriate, you could even try
CullThreadPerCameraDrawThreadPerContext if you have plenty of cores to
throw at it.

In 3.6.x you also have support for explicitly controlling Affinity so
you can lock various threads to particular cores.

Another variable you could play with is that you can set up the
OS/desktop so that one single graphics context can span multiple
cards.

Modern graphics cards are beast so you might well be able to handle
quite a few displays just from one card.

Robert.


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Per Nordqvist
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PostPosted: Wed Oct 03, 2018 2:27 pm    Post subject:
osg apps on gpu cluster
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Thank you Robert, these are great leads, will check them out.


There is one more variant I wonder about:
If I run two osg apps on one screen, with multiple graphics cards,
can I then share the loads between the GPUs?
Something like "GPU Affinity"?


Kind regards
Per





On Tue, 2 Oct 2018 at 09:54, Robert Osfield < (
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Quote:
Hi Nick & Per,

On Tue, 2 Oct 2018 at 06:12, Per Nordqvist < (
Only registered users can see emails on this board!
Get registred or enter the forums!
)> wrote:
Quote:
I and Nick are working to utilize as much of the GPUs as possible, either on single machine or cluster.
So hardware is not yet decided, but let's assume ubuntu 16+, multiple modern Nvidia gaming cards, but still single screen.

osgViewer has been written from the ground up to support multiple GPUs
on a single machine with a single application.

The basic concept is the View's master Camera controls the overall
view, and a series of slave Camera's assign to the View handle the
rendering for each graphics card/display.  The osgwindow example is
the simplistic example of this in action.  A search for addSlave in
the OSG codebase will reveal lots of other examples of it in action -
it can be used for a wide range of tasks.

The OSG out of the box will default to DrawThreadPerContext
ThreadingModel on modern machines, you might find
CullDrawThreadPerContext more appropriate, you could even try
CullThreadPerCameraDrawThreadPerContext if you have plenty of cores to
throw at it.

In 3.6.x you also have support for explicitly controlling Affinity so
you can lock various threads to particular cores.

Another variable you could play with is that you can set up the
OS/desktop so that one single graphics context can span multiple
cards.

Modern graphics cards are beast so you might well be able to handle
quite a few displays just from one card.

Robert.
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robertosfield
OSG Project Lead


Joined: 18 Mar 2009
Posts: 12145

PostPosted: Wed Oct 03, 2018 2:57 pm    Post subject:
osg apps on gpu cluster
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Hi Per,

On Wed, 3 Oct 2018 at 15:27, Per Nordqvist <> wrote:
Quote:
There is one more variant I wonder about:
If I run two osg apps on one screen, with multiple graphics cards,
can I then share the loads between the GPUs?
Something like "GPU Affinity"?

There are various implementation of doing this, with varying levels of
hardware/driver support. This is historical known as SLI.

Personally, I double avoid the complexity as I doubt for vis-sim use
case it's going to help too much.

Robert.


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d_a_heitbrink (David Heitbrink)
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Joined: 23 Sep 2013
Posts: 52

PostPosted: Thu Oct 04, 2018 8:41 pm    Post subject:
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GPU affinity is really only available with Quadro cards. AMD has there own system that is a little more complicated, and has a few more features....but I am not really experienced with those, and I believe they are only usable on the FirePro/Radeon Pro cards.

We have found setting the GPU affinity is an absolute must for multi GPU systems on windows.

Basically from what I understand, windows will by default dispatch the OpenGL commands to what it thinks is the fastest GPU in the system, then copies the result to the other GPU(s). Linux by default dispatches the commands to the GPU attached to the display the window is on......so setting the GPU affinity is most likely only worth while if you are using windows.

FYI I think this was the talk I sat through on the subject:
https://docplayer.net/29825650-Programming-multi-gpus-for-scalable-rendering-shalini-venkataraman-senior-applied-engineer-nvidia.html

I do have an modification of OSG I could share that sets the GPU affinity mask.....but its ugly.

You might also have to think about synchronization if you are driving multiple projectors that are blended to form a single image...and if you have a decent amount of motion, you can get noticeable tearing in the blend regions.
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Trajce Nikolov NICK
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PostPosted: Fri Oct 05, 2018 6:45 am    Post subject:
osg apps on gpu cluster
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Thanks David,


Quote:
You might also have to think about synchronization if you are driving multiple projectors that are blended to form a single image...and if you have a decent amount of motion, you can get noticeable tearing in the blend regions.


The output is not that much important in our case and there are no blending or such (projectors etc). Anyway, this is the info I believe we need to start investigate ...


Thanks again !


Cheers,
Nick


p.s.

Quote:
I do have an modification of OSG I could share that sets the GPU affinity mask.....but its ugly.

Anything will help at this point Smile



On Thu, Oct 4, 2018 at 10:50 PM David Heitbrink < (
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Quote:
GPU affinity is really only available with Quadro cards. AMD has there own system that is a little more complicated, and has a few more features....but I am not really experienced with those, and I believe they are only usable on the FirePro/Radeon Pro cards.

We have found setting the GPU affinity is an absolute must for multi GPU systems on windows.

Basically from what I understand, windows will by default dispatch the OpenGL commands to what it thinks is the fastest GPU in the system, then copies the result to the other GPU(s). Linux by default dispatches the commands to the GPU attached to the display the window is on......so setting the GPU affinity is most likely only worth while if you are using windows.

FYI I think this was the talk I sat through on the subject:
https://docplayer.net/29825650-Programming-multi-gpus-for-scalable-rendering-shalini-venkataraman-senior-applied-engineer-nvidia.html

I do have an modification of OSG I could share that sets the GPU affinity mask.....but its ugly.

You might also have to think about synchronization if you are driving multiple projectors that are blended to form a single image...and if you have a decent amount of motion, you can get noticeable tearing in the blend regions.

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http://forum.openscenegraph.org/viewtopic.php?p=75038#75038





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