Add Multi-Rail Support Libfabric Transport #19
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
CUDA 11.3 released cuFlushGPUDirectRDMAWrites API which takes the place of the host transport enforce_cst api. NVSHMEM no longer supports CUDA 11, so these legacy API's can be removed. Signed-off-by: Seth Zegelstein <[email protected]>
The previous is_proxy variable equals qp_index. Change the name everywhere for consistency. Signed-off-by: Seth Zegelstein <[email protected]>
Attempt to request FI_PROGRESS_AUTO to see if the libfabric provider supports it, if it doesn't fall back to FI_PROGRESS_MANUAL. FI_PROGRESS_AUTO means that we do not need to call into the progress engine for submitted operations to complete. This means that we can remove the host endpoint from the progress call, and we only need to progress the host endpoint when user calls nvshmem_quiet() from the host. This allows us to set the threading model as FI_THREAD_COMPELTION because the host only progress the host EP, and the proxy only progresses the proxy EP, leading to compliance with FI_THREAD_COMPLETION. An edge case exists here where the user calls nvshmem_quiet() on the host QP_IDX from a GPU kernel, but this is illegial because the user shouldn't be calling QP API's on QP's not provided to them via the qp creation API's. This patch should offer a performance improvement because it reduces the number of EP's that are progressed in the critical path, and it allows the libfabric provider to reduce locking b/c of threading model FI_THREAD_COMPLETION. Signed-off-by: Seth Zegelstein <[email protected]>
This change implements multi-rail support for the libfabric host proxy transport. The transport changes from having 1 domain with 2 EP's to having 1 host domain on NIC 1 and one proxy domain per NIC. Splitting the host EP and proxy EP into seperate domains was done for simplicity of the code. Every domain resource (including AV) was bound on a 1-1 basis per EP so this change should be a functional no-op. In the future when one implements the QP API on the libfabric host proxy transport, N EP's per domain can be easily extended on this. This code uses a round robin based load balancer to assign messages to NIC's. One NIC will be used for the entire operation call into the libfabric transport (including put-signal), but not including messages that are segmented due to size or MR boundaries. The number of NIC's (domains) per PE are limited by the size of the struct nvshmemt_libfabric_mem_handle_t. A new env variable NVSHMEM_LIBFABRIC_MAX_NIC_PER_PE controls the max number of NIC's per PE. Thank you Justin for contributing an initial implementation of multi-rail which I built on top of. Co-authored-by: Justin Chui <[email protected]> Signed-off-by: Seth Zegelstein <[email protected]>
Contributor
Author
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Making this PR a Draft PR because I have not finished testing yet.