Excessive system RAM usage when rendering with Iray

andya_b341b7c5f5

I am seeing very high system RAM usage while rendering- higher than seems reasonable to me - and wonder if this is normal?

I am running DS 4.9.4.122 Beta on a 3 year old gaming laptop which has 16Gb of system RAM and a GTX980M with 8Gb of memory.  It's running Win 8.1.  I'm rendering a scene with an HDRI, some simple scenery, two G3F with hair and basic clothing.  Before rendering, DS is taking up less than 3Gb system RAM.  When I start rendering this increases till it peaks about 12Gb for DS alone, so about 95% of system RAM is in use in total.  Rendering is still taking place on the GTX980M, which is just as well.  I've seen this with many similar scenes so I doubt it is due to one 'rogue' product.

Does this seem 'normal'?  It seems excessive to me, given the actual rendering is still on the GPU.  What's all this RAM needed for since we are not rendering on the CPU?  If it's not 'normal', what could I do to normalize it such that I could perhaps add another character to the scene, or some less basic clothing?

(Yes, I'll update to 4.11 in due course, just don't need the potential issues right now!)

Richard Haseltine

DS has to prepare the data to be sent to the GPU, so yes it can eat a lot - though that does sound like a heavy load, have you increased the SubD levels on the figures?

ebergerly

I've seen multipliers of around 2 to 3. In other words, the system RAM is 2 to 3 times the GPU VRAM. 

With big scenes I can get 30+GB of system RAM used, which fills up my 1080ti's 11GB of VRAM 

andya_b341b7c5f5

Richard Haseltine said:

DS has to prepare the data to be sent to the GPU, so yes it can eat a lot - though that does sound like a heavy load, have you increased the SubD levels on the figures?

Thanks, that would make sense, but I don't think so - I mean SubD is 'on' in the sense the resolution is 'High Resolution' not 'Base', but I haven't hiked the SubD level above 1.  I will check though it seems to apply across most, if not all, the scenes I am rendering and I am sure I haven't routinely pumped up the SubD levels.  I would only do that for a specific purpose, not as a general practice.

andya_b341b7c5f5

ebergerly said:

I've seen multipliers of around 2 to 3. In other words, the system RAM is 2 to 3 times the GPU VRAM. 

With big scenes I can get 30+GB of system RAM used, which fills up my 1080ti's 11GB of VRAM 

OK, interesting.  So not just me, which is reassuring.  My fingers and toes are crossed that the GTX 1080Ti will become more affordable as an end of line item once the 20 series cards come out in force.  If it does I may raid the coffers and splurge on something with one of those (or maybe two 1080s) and a mountain of system RAM!  Till then, still hoping to reduce RAM usage.

Richard Haseltine

andya_b341b7c5f5 said:

Richard Haseltine said:

DS has to prepare the data to be sent to the GPU, so yes it can eat a lot - though that does sound like a heavy load, have you increased the SubD levels on the figures?

Thanks, that would make sense, but I don't think so - I mean SubD is 'on' in the sense the resolution is 'High Resolution' not 'Base', but I haven't hiked the SubD level above 1.  I will check though it seems to apply across most, if not all, the scenes I am rendering and I am sure I haven't routinely pumped up the SubD levels.  I would only do that for a specific purpose, not as a general practice.

For Iray it's the render SubD level that matters, the plain SubD level is used in the Viewport (and for export).

andya_b341b7c5f5

Richard Haseltine said:

andya_b341b7c5f5 said:

Richard Haseltine said:

DS has to prepare the data to be sent to the GPU, so yes it can eat a lot - though that does sound like a heavy load, have you increased the SubD levels on the figures?

Thanks, that would make sense, but I don't think so - I mean SubD is 'on' in the sense the resolution is 'High Resolution' not 'Base', but I haven't hiked the SubD level above 1.  I will check though it seems to apply across most, if not all, the scenes I am rendering and I am sure I haven't routinely pumped up the SubD levels.  I would only do that for a specific purpose, not as a general practice.

For Iray it's the render SubD level that matters, the plain SubD level is used in the Viewport (and for export).

OK, so I have never knowingly changed the render SubD, and it has never been more than 2 whenever I have looked at it. So, unless a lot of products set this higher by default...