Release/v26.5#90
Merged
Merged
Conversation
The dispatch/MLP MoE activations are already expert-sharded via activation_exp. Since AI-Hypercomputer#4007, their batch dim also maps to activation_batch_moe, which includes 'expert'. Under single-node expert parallelism (ici_expert_parallelism=-1) this double-maps two tensor dims onto the 'expert' mesh axis, so GSPMD falls back from expert-parallel AllToAll to FSDP-style AllGather+ReduceScatter, regressing throughput for few-large-expert models (e.g. Mixtral-8x7b: ~7.4k -> ~10.9k tok/s/device at bs=11 on 8x MI355X). Add a config flag moe_dispatch_no_expert_sharding (default false) that selects a new activation_batch_no_exp rule ([data, fsdp, fsdp_transpose], no 'expert') for the training dispatch/MLP batch axis. Enable it for mixtral-8x7b. Default-false keeps every other model and all TPU/non-EP paths byte-identical; the flag only changes sharding when the 'expert' mesh axis size > 1.
…e-expert geometry as 8x7b, so it benefits from the same expert-parallel MoE dispatch/MLP sharding.
…oe_dispatch_no_expert_sharding the expert dim is sharded by 'expert' and the batch dim is not, guarding the expert-parallel dispatch/MLP sharding.
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
Description
Start with a short description of what the PR does and how this is a change from
the past.
The rest of the description includes relevant details and context, examples:
If the change fixes a bug or a Github issue, please include a link, e.g.,:
FIXES: b/123456
FIXES: #123456
You can also provide a comma-separated list. If you don't want to close a bug but
simply to reference it, use BUGS, e.g.:
BUGS: b/123456
Notice 1: Once all tests pass, the "pull ready" label will automatically be assigned.
This label is used for administrative purposes. Please do not add it manually.
Notice 2: For external contributions, our settings currently require an approval from a MaxText maintainer to trigger CI tests.
Tests
Please describe how you tested this change, and include any instructions and/or
commands to reproduce.
Checklist
Before submitting this PR, please make sure (put X in square brackets):
gemini-reviewlabel.