Add lock in prefill and generate to prevent starvation #126
Conversation
This file contains 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
wang2yn84
reviewed
Jun 13, 2024
Based on practice (my tests ), we don't need do a lock for insert. The insert resource in minimal (no compute, only a slot pre allocated) resource, it doesn't block prefill or vice visa. |
qihqi
approved these changes
Jun 14, 2024
| @@ -38,6 +39,8 @@ def __init__( | |||
| self.batch_size = batch_size | |||
| self.is_disaggregated = is_disaggregated | |||
| self.pod_slice_name = pod_slice_name | |||
| if not self.is_disaggregated: | |||
| self._lock = threading.Lock() | |||
There was a problem hiding this comment.
lets use RLock. For lock if the thread already have the lock and it try to lock again it will deadlock
There was a problem hiding this comment.
Use lock (without R) should be the right way. The jetstream may have the issue before (same thread call prefill or decode concurrently), there is no recursion in prefill or decode code.
If a thread call the both prefill and decode or itself method multiple time without unlock, then there is a bug on jetstream.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
Current issues
In current jetstream orchestrator, decode can start after prefill start but before prefill finished. Jax multiple controller run mix of prefill and decode step at certain time, this will cause deadlock and hang the jax program (suppose there are n chips, prefill wait n -1 prefill finished, decode wait another n -1 decode finish, but neither of them can reach all n finished).
Fix
Add lock in prefill and generate to make sure the two function are executed in sequential.
Long term fix
Refactor jetstream and let orchestrator handle the function call correctly in multiple controller jax.