I've read this more like that you can use FF h/w for this, including already existing h/w if needed, but you're likely to have better results on a GPU anyway.
DirectStorage GPU Decompression, RTX IO, Smart Access Storage
- Thread starter DavidGraham
- Start date
This is what I like to see (check the frametime graphs at the bottom)
On the CPU you can easily tell when the decompression is happening with that large cluster of spikes. On the GPU you can see two spikes, and those only happen because the scene is being reloaded, and then displayed after loading. In the middle, it's comparatively perfectly smooth as it decompresses. This test obviously shows a blank screen while it loads, but you can imagine that in streaming during gameplay scenarios... on the CPU you might see some hitches, while on the GPU it would remain perfectly smooth.
------------------------CPU---------------------------------------------------------GPU----------------------------
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On the CPU you can easily tell when the decompression is happening with that large cluster of spikes. On the GPU you can see two spikes, and those only happen because the scene is being reloaded, and then displayed after loading. In the middle, it's comparatively perfectly smooth as it decompresses. This test obviously shows a blank screen while it loads, but you can imagine that in streaming during gameplay scenarios... on the CPU you might see some hitches, while on the GPU it would remain perfectly smooth.
------------------------CPU---------------------------------------------------------GPU----------------------------
-
This depends on the decompression implementation I suppose. CPU decompression can (ans should really in case of streaming) certainly be implemented without locking rendering thread(s).
The bigger issue here is that GDeflate don't seem to run that well on CPUs at the moment which may be an issue when choosing on how to store the assets in the first place.
Yea you're right, but there are some games out there which don't do the best job of this.
Now I think Forza Horizon 5 is a good example of what I'm saying. The game has loading screens, but once it loads the open world, you're basically in there. If you fast travel somewhere, you'll get another quick loading screen, but it's super fast. FH5 uses videos for their traditional loading screens.. and of course the stuttering that happens during these loads is inconsequential, because you're not playing anything. However... when you enter races, the game cuts to your vehicle in the showroom, in real-time, and does some panning around.. and this loading can cause stuttering.. like this:
(1h29m)
There's also games which load behind pre-rendered video, and often times those can have stuttering issues as well. I'm thinking GPU decompression helps solve a lot of those potential stutters.
I'm struggling to follow that video tbh but I would assume that the GPU is simply being bottlenecked there by the SSD throughput whereas the CPU is clearly unable to keep up with the SSD throughput. I'm not seeing where you are getting the 90% GPU usage from though? I saw variation between 55-81% during what I assume was the actual decompression stage but it's not clear what was changing between runs to vary that usage.
Intels Demo for example shows a 2.7x speed up on an Arc A770 over a 12900K while reducing CPU usage from 100% to 0%.
Seems to run well enough to be a reasonable solution for even a cpu.
Guess if you're going to be using this, your likely to have a reasonable minimum spec for your game.
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Did wonder if one of the reasons we hadn't heard much about BCPack was due to waiting for a compatible PC way of packaging assets.
So even if this isn't directly BCPack compatible, by the sounds of it you may organise the assets the same, and maybe use gDeflate on PC and BCPack on XS.
Could see Forza:M being first to make big use of DS in full on PC & console.
So even if this isn't directly BCPack compatible, by the sounds of it you may organise the assets the same, and maybe use gDeflate on PC and BCPack on XS.
Could see Forza:M being first to make big use of DS in full on PC & console.
Thanks, couldn't remember if XS supported deflate or not.
I've given up until it happens of BCPack being on PC as everything around BCPack in general has been extremely quiet and NDA'd.
But the way you have to package /compress for gDeflate sounds like it would be similar for BCPack due to tile streaming.
So could use gDeflate on PC and BCPack on console, but the assets are structured the same way.
Until current gen only, probably not been big enough reasons to implement it.
Yah, looking at it again your numbers look to be more correct.
It's DirectStorage it literally sits under DirectX.
So nothing to do with PS.
MS is about getting people to use their GDK for cross platform development PC and Xbox. So I expect them to make it as easy as possible.
I wasn't too sure if gDeflate would work well at 64k tile granularity so was half expecting it to be at the mip level.
But in terms of wider development as in PS5, gDeflate will be open source with a reference implementation available.
But even if it's not used on PS5, I expect a similar streaming method to be available making use of its hardware.
Just use different compression format.
With the era of cross gen I don't think there's been much need in getting JIT streaming working on current gen.
Hoping that changes with current gen only & this release.
LordVulkan
Newcomer
GDflate/Deflate and BCPack have completely different purposes.
GDFlate/Deflate (like RAD's Oodle Kraken) are lossless data compression formats, can be used on everything and always apply to all the data you send to the GPU and can be implemented in HW blocks like PS5 and Xbox consoles have done.
BCPack and others (such as RAD's Oodle Texture) are texture compression encoding algorithms for S3TC formats (see https://en.wikipedia.org/wiki/S3_Texture_Compression), these formats are very widespread and are what the GPU ends up needing in VRAM for rendeing. They are not decompressed before being written to VRAM.
So, every common workflow should first compress the textures to an S3TC format using whatever texture compression algorithm (on PC you can use Basis Universal which Bionomial donated to Khronos for standardization a few years ago) and then package everything with the lossless data compression algorithm.
This has been the common workflow for years but the CPU was in charge of decoding each data stream, now we have dedicated HW blocks for that purpose on consoles and, on PC, now the GPU can do the job itself many times faster than CPU that allows to catch up with NVMe bandwidth capabilities.
Thanks for that.
Understand what you mean, but this bit was a bit unclear, so for any one else.
BCPack & kraken are decompressed resulting in S3TC which is also a compression format that is directly readable by the gpu so doesn't need to be decompressed also.
Hopefully not misleading here.
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So does that mean there all compatible with eachother.
I.e use gDeflate inside BCPack, kraken inside BCPack also?
Reason I ask is that if it was just at the mip level that easily makes sense, but these are dealing with tiles inside of the mips? Guess they all have that ability.
It's the only thing you can do, massage the hardware format's bitstream to make it more compressable by general purpose coders. You can not compete with the hardware sampler's speed of decoding, and drop that representation entirely. In the most extreme case, Binomial's, they invent internal representations which are entirely different but fully transcodable to hardware formats. Not only to make them more compressible, but also to make them scalable for quality.
Maybe one day there can be i/o shaders, that means programmable samplers/input blocks, and programmable rops/output blocks. Then you can truly approach rate-distortion limits (with "rate" also be computation cost, or overall latency "cost", not just size).
Ext3h
Regular
"Existing IP" refers to ready-to-license building blocks. Unfortunately not to already existing or even integrated FF H/W.
Actually that's only the fallback solution.
Unless I'm entirely mistaken, then AMD has already demonstrated that they can stream directly to BAR from NVMe, for a specific combination of own chipset, CPU generation, GPU and qualified NVMe devices which work with their own (not the MS one) NVMe driver, but still with standard NTFS.
It's not as tricky as people tend to make it for a vendor which has control over all the involved components. Just requires clean tracking of resources over multiple driver stacks. The file system overhead some are so afraid of are not that bad when you can just build lookup tables in RAM as a one-time cost per application. Even alignment issues and alike don't make much of a difference for typical asset sizes - just something the GPU driver needs to mask.
Not expecting it from Intel any time soon though, their driver stack looks ... fractured. And NVidia will likely struggle until this is eventually properly standardized.
Going to system RAM does have a huge impact on the CPU after all. With PCIe 4.0 4x on the storage side, that's still 16GB/s of memory bandwidth (half-duplex!) burnt. Accounting for some inefficiencies, that's almost one DDR4 memory channels bandwidth worth lost. One of these nasty details you won't see in a synthetic benchmark (due to lack of easily accessible load statistics!), but which will bite you later on.
BC itself doesn't exactly have a place in the storage formats any more. It doesn't produce a bitstream suitable for further packing.
You would be using any of the image formats suitable for (respectively their compression ends in) deflate compression (there are many!). Requires some additional post-processing on the GPU side, in order to reverse the additonal transformations which were enabling the image to achieve an actually decent compression rate in the first place.
What we are seeing showcased right now - GDeflate being applied directly to an RGB bitmap or vertex buffers - represents still a very early stage of development. Expect compression rates to get much better as people figure that out.
Chaining a BC encoder on the GPU, after the decompression, would be more viable to get the VRAM impact back down to where you originally had it when using BC family compression throughout the entire pipeline.
Without locking - yes. But don't forget about the size of the working set for the read-only lookup tables. Easy to run parallel decompression (from the same parameter set), but likely to trash L2/L3 for other workloads.
There is actually one elephant in the room:
What to do with all the target systems not getting an update with official DirectStorage support? Windows 10 is still going to stay for a long, long time.
The way it looks there are some constraints you simply can't work around without it, specifically the reduction of GPU uploads from 4 memory transfers down to 2 or 0 (AMD only).
But you are also facing the need to maintain a common format for your assets. With the current tendency that MS will recommend you to use the IHVs proprietary implementation of GDeflate - that's looking like something you can't even consider targeting for a very long time. The "software fallback" - for now - isn't provided for a significant portion of your target audience either.
So you will be reliant on shipping your own kernels for GDeflate support (and whatever future extensions you will need) as a fallback solution for the foreseeable future.
Using CPU decompression for the fallback path would be a huge mistake, after all at that point you have already dropped at least the previously used texture compressions schemes, now causing a vastly higher load (CPU and caches for decompression, memory and PCIe bandwidth for the now doubled data rates).
Win10 has DirectStorage support. It doesn't have bypass I/O but I don't think that this will mean much.
Not sure what you mean here. GDeflate is a common storage format which is then can be decoded by either IHVs decoders or DX s/w fallback - which I presume will be a GPU compute solution too just not that optimized as a custom IHV provided one may be. CPU decompression is likely a secondary fallback solution here - which you could argue isn't even necessary as a h/w which won't be able to run GPU compute decompressor (SM 6.0) is very unlikely to be able to run a game made for DS 1.1 API.
Ext3h
Regular
It does? Completely missed that. So as long as your GPU is getting driver updates (at all) you should be good? Or is this tied to a specific Windows 10 minor release?
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