Changed scheduler to use deques instead of lists #2290
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WoosukKwon
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Jan 2, 2024
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Hi @NadavShmayo, thanks for submitting the PR! Yes, it seems we should use deque instead of list for the queues in our scheduler. I left some minor comments on the PR. Please take a look at them!
WoosukKwon
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Jan 7, 2024
Hey, sorry for the delayed response. Regarding the changes in the Thanks for the review! 😄 |
hongxiayang
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Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
njhill
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Jan 20, 2024
vllm-project#2290 changed the scheduler seq group lists to be deques for more efficient updates, but missed one place where the `running` deque gets converted back to a list.
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Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
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Currently the scheduler uses lists to store the running, waiting and swapped requests.
When iterating over each state queue we pop the first item and append to a new list, which is not good for performance since each pop is O(N) time complexity, which means the scheduler currently runs in O(N^2) time complexity (a pop happens for each item in the state queue).
Instead of using lists we could use deques, since we can pop the first item from a deque in O(1) time complexity, making the scheduler run in O(N) time complexity instead of O(N^2).
I wasn't sure whether I should keep the same types in the SchedulerOutputs class and cast from a deque to a list before returning the result, but since it seems to work with the SchedulerOutputs contains deques instead of lists I decided to change the types.