varlen combine scheduler #70
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tlrmchlsmth
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Jun 11, 2025
tlrmchlsmth
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Code looks good to me. Optimization makes sense. Nice work.
Should we try to push this upstream?
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Ya I'm going to make an upstream PR |
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Co-authored-by: Tyler Michael Smith <tysmith@redhat.com> Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
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* varlen combine scheduler Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * move check Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * standard scheduling algo Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better heuristic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better comments Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * put in a more readable heurisitic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * Apply suggestions from code review Co-authored-by: Tyler Michael Smith <tysmith@redhat.com> Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * FA2 8.0 PTX (vllm-project#69) Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> --------- Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> Co-authored-by: Tyler Michael Smith <tysmith@redhat.com>
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* varlen combine scheduler Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * move check Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * standard scheduling algo Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better heuristic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better comments Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * put in a more readable heurisitic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * Apply suggestions from code review Co-authored-by: Tyler Michael Smith <tysmith@redhat.com> Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * FA2 8.0 PTX (#69) Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> --------- Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> Co-authored-by: Tyler Michael Smith <tysmith@redhat.com>
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* varlen combine scheduler Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * move check Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * standard scheduling algo Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better heuristic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * better comments Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * cleanup Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * put in a more readable heurisitic Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * Apply suggestions from code review Co-authored-by: Tyler Michael Smith <tysmith@redhat.com> Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> * FA2 8.0 PTX (#69) Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> --------- Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com> Co-authored-by: Tyler Michael Smith <tysmith@redhat.com> Signed-off-by: Jay Shah <jayhshah@gmail.com>
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Improvement to address: vllm-project/vllm#18619 (comment)
When running the combine with large batch that is almost entirely decode with 1 prefill the previous grid was excessively large making the combine kernel take a long time.
Before this PR the grid size for combine would be
cdiv(max_seqlen_q * num_heads, kBlockM) x batch_sizeafter this PR its(cdiv(total_q * num_heads, kBlockM) + batch_size) x 1which scales much better for large batches that are primarily made up of decodes.e.g. if we have a batch of 256 where the q_seqlens are [600] + [1] * 255, (assuming num_heads 8 and kBlockM 8)
before this PR the grid would be:
cdiv(600 * 8, 8) x 256 = 153600after this PR the grid is:
cdiv(855 * 8, 8) + 256 x 1 = 1111