[JNI] remove rmm argument to set rw access for fabric handles #17553
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Signed-off-by: Alessandro Bellina <[email protected]>
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bdice
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Dec 9, 2024
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ttnghia
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Dec 9, 2024
jlowe
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Dec 9, 2024
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Closes #1753 It is a follow up from #1743 I would like for rapidsai/cudf#17553 to merge first, that way I don't break the build. I've learned that I was using `cudaMemPoolSetAccess` incorrectly. This API should only be used from a `peer` device, not from the device that created the pool. This is the reason why calling `cudaMemPoolSetAccess` with none throws an error as documented here #1753. I have tested that I can still export the fabric handles and import them using UCX in a peer device with the default access that pool owner device gets (read+write is the default). Note that this read+write default access cannot be revoked from the owner, as it wouldn't make sense to have memory that nobody has access to, but peers can call `cudaMemPoolSetAccess` to gain read+write access or to stop accessing (none) a peer's pool memory. Authors: - Alessandro Bellina (https://github.com/abellina) Approvers: - Bradley Dice (https://github.com/bdice) URL: #1754
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Description
This is a follow up from #17526, where fabric handles can be enabled from RMM. That PR also sets the memory access protection flag (
cudaMemPoolSetAccess), but I have learned that this second flag is not needed from the owner device. In fact, it causes confusion because the owning device fails to call this function with some of the flags (access none).cudaMemPoolSetAccessis meant to only be called from peer processes that have imported the pool's handle. In our case, UCX handles this from the peer's side and it does not need to be anywhere in RMM or cuDF.Sorry for the noise. I'd like to get this fix in, and then I am going to fix RMM by removing that API.
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