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@mgoin mgoin commented Jul 4, 2025

Purpose

All the call sites for fused_marlin_moe for FP8 and FP4 MoE methods were neglecting to pass in the layer.workspace that was pre-allocated by the prepare_moe_fp8_layer_for_marlin and prepare_moe_fp4_layer_for_marlin functions.

This means that we were potentially allocating a new workspace (albeit small) on each fused_marlin_moe call

if workspace is None:
workspace = marlin_make_workspace_new(hidden_states.device, 4)

Test Plan

CI and manual correctness tests. Will measure performance to look for potential small benefit

Test Result

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Summary of Changes

Hello @mgoin, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements a targeted performance optimization for Marlin Mixture-of-Experts (MoE) operations, specifically for FP8 and FP4 quantization types. The core change involves modifying the call sites of the fused_marlin_moe function to explicitly pass and reuse a pre-allocated workspace, thereby eliminating redundant memory allocations and enhancing the overall efficiency of these compute-intensive operations.

Highlights

  • Performance Optimization: Ensured that fused_marlin_moe calls for FP8 and FP4 Mixture-of-Experts (MoE) operations consistently reuse a pre-allocated layer.workspace. This prevents redundant memory allocations during each call, leading to improved efficiency.
  • Memory Efficiency: Addressed an oversight where fused_marlin_moe calls were not explicitly passed the pre-allocated workspace, potentially leading to unnecessary memory allocations. The fix ensures the existing workspace is utilized.
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Code Review

This pull request correctly addresses a performance issue by reusing a pre-allocated workspace for FP8 and FP4 Marlin MoE, which avoids repeated memory allocations. The changes are consistently applied across all relevant call sites in compressed_tensors_moe.py, fp8.py, and modelopt.py. The implementation correctly passes the layer.workspace attribute, which is initialized during the layer setup. The code is clean, and the fix is straightforward and correct. I find no issues with this change.

@mgoin mgoin added the ready ONLY add when PR is ready to merge/full CI is needed label Sep 16, 2025
@mgoin mgoin marked this pull request as ready for review September 16, 2025 01:59
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LGTM, thanks for the work!

@mgoin mgoin merged commit dbebb7f into vllm-project:main Sep 16, 2025
47 checks passed
@mgoin mgoin deleted the reuse-workspace-marlin-moe-fp8+fp4 branch September 16, 2025 21:45
FeiDaLI pushed a commit to FeiDaLI/vllm that referenced this pull request Sep 25, 2025
Signed-off-by: mgoin <[email protected]>
Signed-off-by: Michael Goin <[email protected]>
Co-authored-by: Wentao Ye <[email protected]>
charlifu pushed a commit to ROCm/vllm that referenced this pull request Sep 25, 2025
Signed-off-by: mgoin <[email protected]>
Signed-off-by: Michael Goin <[email protected]>
Co-authored-by: Wentao Ye <[email protected]>
Signed-off-by: charlifu <[email protected]>
xuebwang-amd pushed a commit to xuebwang-amd/vllm that referenced this pull request Oct 10, 2025
Signed-off-by: mgoin <[email protected]>
Signed-off-by: Michael Goin <[email protected]>
Co-authored-by: Wentao Ye <[email protected]>
Signed-off-by: xuebwang-amd <[email protected]>
choprahetarth pushed a commit to Tandemn-Labs/vllm that referenced this pull request Oct 11, 2025
Signed-off-by: mgoin <[email protected]>
Signed-off-by: Michael Goin <[email protected]>
Co-authored-by: Wentao Ye <[email protected]>
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