CPU usage whilst using GPU acceleration

General questions about Indigo, the scene format, rendering etc...
Post Reply
13 posts • Page 1 of 1
Stinkie
Indigo 100
Posts: 616
Joined: Sat Oct 27, 2007 9:22 pm

CPU usage whilst using GPU acceleration

Post by Stinkie » Sat Nov 17, 2012 6:50 am

Quick question: is it normal for the cpu usage to be relatively low while gpu acceleration is turned on?

User avatar
Polinalkrimizei
Posts: 647
Joined: Sat May 02, 2009 6:59 am

Re: CPU usage whilst using GPU acceleration

Post by Polinalkrimizei » Sat Nov 17, 2012 7:39 am

Quick answer: That depends.

Sometimes my CPU goes as low as around 70% when using GPU, that depends on its power (the faster the CPU the more data it will shovel to the GPU and the more busy it will get).

How low is your CPU usage? What are your specs? Is it a complex scene?

Stinkie
Indigo 100
Posts: 616
Joined: Sat Oct 27, 2007 9:22 pm

Re: CPU usage whilst using GPU acceleration

Post by Stinkie » Sat Nov 17, 2012 8:59 am

Pretty low. It rarely goes over 50%, except for when the image is being refreshed. My cpu is a i7-3930K, my gpu a N680GTX Twin Frozr 4GD5/OC. Scene complexity isn't very high, I think -my SketchUp models are generally fairly simple.

User avatar
Pibuz
1st Place 100
Posts: 2646
Joined: Tue Dec 11, 2007 7:58 am
Location: Padua, Italy
3D Software: SketchUp

Re: CPU usage whilst using GPU acceleration

Post by Pibuz » Sun Nov 18, 2012 2:46 am

Sounds like a so-called bottle neck: I'm not a technician, but sounds like your GPU is very fast compared to your CPU power (which is fair good already, I'd say). Lycium will surely add some more precise info :)

User avatar
dag
Posts: 189
Joined: Tue Feb 02, 2010 2:28 am

Re: CPU usage whilst using GPU acceleration

Post by dag » Sun Nov 18, 2012 3:28 am

Pibuz wrote:sounds like your GPU is very fast compared to your CPU power
Wouldn't then the cpu use more since it has to feed the gpu faster?

My cpu uses 100% and that's an i7 with hd 5770.
Are you using all cpu threads?

Stinkie
Indigo 100
Posts: 616
Joined: Sat Oct 27, 2007 9:22 pm

Re: CPU usage whilst using GPU acceleration

Post by Stinkie » Sun Nov 18, 2012 3:42 am

Pibuz wrote:Sounds like a so-called bottle neck (...)
That's what I figured, though I'm no expert either. Dammit, my gpu is too fast! Ah, luxury problems! :)

User avatar
Pibuz
1st Place 100
Posts: 2646
Joined: Tue Dec 11, 2007 7:58 am
Location: Padua, Italy
3D Software: SketchUp

Re: CPU usage whilst using GPU acceleration

Post by Pibuz » Sun Nov 18, 2012 3:48 am

er..busted! :lol: :lol:

I don't know what I'm talking about precisely, I just liked the bottle-neck figure of speech :lol:
I only know I'm currently experiencing a similar issue, running on a machine with a GTX480 and an old q6600 quad core

User avatar
CTZn
Posts: 7240
Joined: Thu Nov 16, 2006 4:34 pm
Location: Paris, France

Re: CPU usage whilst using GPU acceleration

Post by CTZn » Sun Nov 18, 2012 5:46 am

The case is sounding fishy to me to be honest.

Ideally, when the CPU is not at full throttle that would mean that the GPU can not process the CPU data fast enough.

That's unlikely, given the common reports of modern GPU's being throttled by the CPU, not the other way around.
Stinkie wrote:Quick question: is it normal for the cpu usage to be relatively low while gpu acceleration is turned on?
No, not according to a mass of reported behaviour.

So yes it's a bottleneck, but not as one would expect, hence the topic isn't it.

I'm not an hardware amateur either, but if the "Twin" refers to a double core embedding perhaps is Indigo currently able to mobilize just one.

Did you download the latest drivers ? dag's suggestion is making sense as well, just in case.

To be clarified IMHO.
obsolete asset

Stinkie
Indigo 100
Posts: 616
Joined: Sat Oct 27, 2007 9:22 pm

Re: CPU usage whilst using GPU acceleration

Post by Stinkie » Sun Nov 18, 2012 8:22 am

Downloaded the latest drivers -no change. I checked whether I'm using all threads, and I am.

User avatar
Zom-B
1st Place 100
Posts: 4700
Joined: Tue Jul 04, 2006 4:18 pm
Location: ´'`\_(ò_Ó)_/´'`
Contact:

Re: CPU usage whilst using GPU acceleration

Post by Zom-B » Sun Nov 18, 2012 11:03 am

CPU & GPU usage is very related to the scene! A exterior often lets your GPU cry, since a lot of rays get bounced back into space and killed early and for interiors and endless bouncing rays the GPU needs to wait for the CPU.
(I hope I don't mixed that up!)
polygonmanufaktur.de

User avatar
galinette
1st Place Winner
Posts: 923
Joined: Sat Jan 09, 2010 1:39 am
Location: Nantes, France
Contact:

Re: CPU usage whilst using GPU acceleration

Post by galinette » Mon Nov 19, 2012 8:18 pm

Don't forget the bus and I/Os when thinking about bottleneck. CPU and GPU are not the only two components that can limit the speed : the bus between the two has a limited bandwidth and non-zero latency, that can clamp performances.

Etienne
Eclat-Digital Research
http://www.eclat-digital.com

Stinkie
Indigo 100
Posts: 616
Joined: Sat Oct 27, 2007 9:22 pm

Re: CPU usage whilst using GPU acceleration

Post by Stinkie » Tue Nov 20, 2012 7:55 am

Guess I'm scr*wed. 8)

User avatar
CADMonkey
Posts: 22
Joined: Thu Sep 09, 2010 9:45 pm
Location: West Yorkshire

Re: CPU usage whilst using GPU acceleration

Post by CADMonkey » Wed Nov 21, 2012 9:32 pm

I find this also.

I can quite happy work on other projects whilst rendering using GPU. (I actually find it pretty handy)

my system is i7-2600 (3.4GHz)
16 GB ram
Nvidia Qadro 4000 GFX card

Post Reply
13 posts • Page 1 of 1

Who is online

Users browsing this forum: No registered users and 25 guests