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Are there any real world examples of applications taking advantage of 128GB+ of VRAM?

theorist9 said:
However, the GPUs in the DGX are connected by NVLink, so I thought that was answered (in the negative) by your quote from the NVIDIA developer, who said "NVLink provides a fast interconnect between GPUs, but does not aggregate those GPUs into a single logical device."
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I read this as each of the dGPU will have their own kernel processes running, but each of those processes can potentially read data off other dGPU's VRAMs. If this is the case, probably have to code the dGPU kernels to understand this fact and make the GPU codes more complicated.

Apple's UMA with UltraFusion makes this a lot more elegant IMHO.
 
theorist9 said:
It would be cool if they could, but what about this?:

Plus Maxxon (the maker of Redshift) says:

"Redshift does not combine the VRAM when using multiple GPUs. This is a limitation of current GPU technology and not related to Redshift in particular." [emphasis mine.]

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Read up on nvlink (section 3) for octane. Basically octane treats the 2nd nvlink GPU’s vram as fast out of core memory (nvlink in the 2xxx series has about 100 GBps bandwith - much faster than PCI-e and system ram) but you will need around 3x-4x System ram to fully saturate the combined vram of nvlinked cards and keep octane chugging along.
 
senttoschool said:
Why would this ratio be linear? I assume that macOS takes a static amount of the memory but macOS does not take more memory if you have more.
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I tried searching for the 128 GB ultra redshift to see if the ratio holds but didn’t find much info.
It would be a relief actually if the ratio doesn’t hold at higher ram capacities.
 
singhs.apps said:
I tried searching for the 128 GB ultra redshift to see if the ratio holds but didn’t find much info.
It would be a relief actually if the ratio doesn’t hold at higher ram capacities.
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Everything I know about software engineering suggests that apps do not take a linear amount of RAM. If it does, there's some really bad programming going on.

If a Mac has 1TB of RAM, does macOS automatically consume 200GB of RAM? No.
 
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senttoschool said:
Everything I know about software engineering suggests that apps do not take a linear amount of RAM. If it does, there's some really bad programming going on.

If a Mac has 1TB of RAM, does macOS automatically consume 200GB of RAM? No.
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I could be wrong but got the sense that redshift couldn’t eat up more ram because the system didn’t allow the extra headroom.
Needs more investigation and less opaque responses from Apple and developers alike.
 
singhs.apps said:
I tried searching for the 128 GB ultra redshift to see if the ratio holds but didn’t find much info.
It would be a relief actually if the ratio doesn’t hold at higher ram capacities.
Click to expand...
Here you go

47229207-3E0A-4FC8-BC58-808C14D5235A.jpeg
 
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singhs.apps said:
So the ratio holds (kind of).
I wonder if it’s an OS level hard limit or Redshift is the limiting factor.
Also, how is the scaling viz the M1 Max 64 GB variety?
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It doesn't hold.

64GB - 42GB = 22GB
128GB - 96GB = 32GB

Either way, I'm not sure what's going on here. macOS does not/should not take up more RAM if you have more RAM. It's possible that these tests are not standardized and one person ran it with more apps opened than the other.
 
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senttoschool said:
It doesn't hold.

64GB - 42GB = 22GB
128GB - 96GB = 32GB

Either way, I'm not sure what's going on here. macOS does not/should not take up more RAM if you have more RAM. It's possible that these tests are not standardized and one person ran it with more apps opened than the other.
Click to expand...

It appears the ratio holds. A user reporting 48 Gb available to redshift ( 6GB up from 42 GB if I remember correctly ) on his m1 max. I have a m1 max MBP. Will test myself later this week.
 
singhs.apps said:
It appears the ratio holds. A user reporting 48 Gb available to redshift ( 6GB up from 42 GB if I remember correctly ) on his m1 max. I have a m1 max MBP. Will test myself later this week.
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Really depends on the applications being used. Some applications allocate more buffer from memory if they see the system have more to offer, thus reducing the "VRAM" for the GPU.

If we just look at memory consumed when macOS boots up, we will likely see a plateauing of memory used if plotting memory used against total memory installed. The larger the amount of memory installed, the more memory is required by the OS to keep track of all the memory pages, but as the amount of memory grows, it will outpace the memory used, without any apps asking for memory.

Most OSes will also reserve some memory for essential services like networking, file I/O, etc, so the more memory that's installed, they more will be reserved, but I would think it will also plateau off after a certain size. But if there's more memory not use when a file is loaded, most OSes will just use the free memory up to cache the files loaded, but these allocated memory regions will be freed up if applications ask for memory if there're no more free regions available.

In short, I don't think there's any magic ratio.
 
quarkysg said:
In short, I don't think there's any magic ratio.
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No one’s talking about any magic ratio.
If the same task is conducted on two systems, one of which has higher amount of ram, all else being equal, it’s fair to expect more ram is made available for said task in the system with the higher amount, if needed.

But in both cases only 75% of system ram is allocated. Doesn’t matter if system ram is 64GB or 128 GB.
64 GB - 48 GB allocated
128 GB - 96 GB allocated
 
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