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cl_ext_buffer_device_address #1159

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pjaaskel
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@pjaaskel pjaaskel commented May 7, 2024

The basic cl_mem buffer API doesn't enable access to the underlying raw pointers in the device memory, preventing its use in host side data structures that need pointer references to objects. This API adds a minimal increment on top of cl_mem that provides such capabilities.

The version 0.1.0 is implemented in PoCL and rusticl for prototyping, but everything's still up for discussion. chipStar is the first client that uses the API.

@karolherbst
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any motivation to get this merged? Or anything else needed to discuss before merging this? Could also try to bring it up at the CL WG if needed.

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any motivation to get this merged? Or anything else needed to discuss before merging this? Could also try to bring it up at the CL WG if needed.

Yep, this is still being discussed in the WG. I personally think it's useful as is and shouldn't harm anything if merged as it even has 2 implementations now.

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@pjaaskel
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Thanks @SunSerega

@SunSerega
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Alright, and now the problem I found in #1171 is visible here because the Presubmit workflow has been properly rerun.

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pjaaskel commented Sep 4, 2024

One thing I'm wondering about is how should clCreateSubBuffer behave when being executed on a bda memory object? Should it fail or succeed? I'm fine with either, just wondering if some of the behavior needs to be formalized.

CL_MEM_DEVICE_PTR_EXT and CL_MEM_DEVICE_PTRS_EXT comes to my mind, which should probably return the address + the sub buffer offset, at least that's how I have implemented it so far.

Yes, this was the idea. I'll add a mention in the next update.

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pjaaskel commented Sep 9, 2024

Updated according to @karolherbst comments.

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I've already implemented the extension fully in rusticl/mesa (including sharing the same address across devices) and I think it's fine, however I'd still urge to address the concerns I have for layered implementations implementing it on top of Vulkan. I've already considered the constraints when implementing it, however I think it's better to provide clients to query if address sharing across multiple devices is supported or not.

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pjaaskel and others added 4 commits September 24, 2024 15:25
The basic cl_mem buffer API doesn't enable access to the underlying raw
pointers in the device memory, preventing its use in host side
data structures that need pointer references to objects.
This API adds a minimal increment on top of cl_mem that provides such
capabilities.

The version 0.1.0 is implemented in PoCL and rusticl for prototyping,
but everything's still up for discussion. chipStar is the first client
that uses the API.
Co-authored-by: Sun Serega <sunserega2@gmail.com>
Changed the CL_MEM_DEVICE_ADDRESS_EXT wording for multi-device
cases "all", not "any", covering a case where not all devices
can ensure the same address across the context. In that case
CL_INVALID_VALUE can be returned.  Defined sub-buffer address
computation to be 'base_addr + origin'. Added error conditions
for clSetKernelExecInfo when the device doesn't support
device pointers.
...and renamed them to CL_MEM_DEVICE_SHARED_ADDRESS_EXT and
CL_MEM_DEVICE_PRIVATE_ADDRESS_EXT. The first one guarantees the
same address across all devices in the context, whereas the latter
allows per-device addresses.
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@pjaaskel
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@SunSerega thanks!

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@karolherbst I asked about this in the CL/memory WG. We need to submit CTS tests and this might be good to go then with this one. Do you have good tests in Rusticl side we could use? The test in PoCL is quite basic (and needs to be updated), but can be used as a starting point also.

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@karolherbst I asked about this in the CL/memory WG. We need to submit CTS tests and this might be good to go then with this one. Do you have good tests in Rusticl side we could use? The test in PoCL is quite basic (and needs to be updated), but can be used as a starting point also.

I haven't written any more tests and only used the one in pocl. But I can probably help out with writing tests here.

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3 participants