vllm - 💡(How to fix) Fix [Performance]: Significant performance degradation v1/reranker under concurrent requests while swiching from v.0.19.1 to v0.20.2 v0.21.1

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============================== CPU Info

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 45 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 24 On-line CPU(s) list: 0-23 Vendor ID: AuthenticAMD Model name: AMD EPYC 9654 96-Core Processor CPU family: 25 Model: 17 Thread(s) per core: 1 Core(s) per socket: 1 Socket(s): 24 Stepping: 1 BogoMIPS: 4792.79 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl tsc_reliable nonstop_tsc cpuid extd_apicid tsc_known_freq pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw topoext invpcid_single ssbd ibrs ibpb ibrs_enhanced vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves avx512_bf16 clzero wbnoinvd arat avx512vbmi umip pku ospke avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid overflow_recov succor fsrm flush_l1d Hypervisor vendor: VMware Virtualization type: full L1d cache: 768 KiB (24 instances) L1i cache: 768 KiB (24 instances) L2 cache: 24 MiB (24 instances) L3 cache: 768 MiB (24 instances) NUMA node(s): 1 NUMA node0 CPU(s): 0-23 Vulnerability Gather data sampling: Not affected Vulnerability Indirect target selection: Not affected Vulnerability Itlb multihit: Not affected Vulnerability L1tf: Not affected Vulnerability Mds: Not affected Vulnerability Meltdown: Not affected Vulnerability Mmio stale data: Not affected Vulnerability Reg file data sampling: Not affected Vulnerability Retbleed: Not affected Vulnerability Spec rstack overflow: Mitigation; safe RET Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Vulnerability Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; STIBP disabled; PBRSB-eIBRS Not affected; BHI Not affected Vulnerability Srbds: Not affected Vulnerability Tsa: Vulnerable: Clear CPU buffers attempted, no microcode Vulnerability Tsx async abort: Not affected Vulnerability Vmscape: Not affected

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Proposal to improve performance

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Report of performance regression

Model: bge-reranker-v2-m3. Here 3 runs of some sample code for 3 version of vllm. Same code, just different version of vllm. Mean Latency(T) - sec using requests Mean Latency(A) - sec using aiohttp

<!--StartFragment--><!DOCTYPE html><p cid="n1919" mdtype="paragraph" class="md-end-block md-p md-focus" style="box-sizing: border-box; line-height: inherit; orphans: 4; margin: 0.8em 0px; white-space: pre-wrap; position: relative; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><span md-inline="plain" class="md-plain md-expand" style="box-sizing: border-box;">(vllm v0.19.1)</span></p><figure class="md-table-fig table-figure" cid="n1920" mdtype="table" style="box-sizing: border-box; margin: 1.2em 0px; overflow-x: auto; max-width: calc(100% + 16px); padding: 0px; cursor: default; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">
СoncurencyTime (A)Time(T)RPS(A)RPS(T)Mean Latency(A)Mean Latency(T)Max Latency(A)Max Latency(T)Min Latency(A)Min Latency(T)
14.493.70.220.273.933.73.933.73.933.7
515.4515.330.320.3311.7711.6315.115.327.677.74
1029.3228.540.340.3520.9520.0428.9728.5311.8710.87
2053.8958.270.370.3435.0840.0653.4958.2413.2620.25
</figure><br class="Apple-interchange-newline"><!--EndFragment--> <!--StartFragment--><!DOCTYPE html><p cid="n1523" mdtype="paragraph" class="md-end-block md-p md-focus" style="box-sizing: border-box; line-height: inherit; orphans: 4; margin: 0.8em 0px; white-space: pre-wrap; position: relative; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><span md-inline="plain" class="md-plain md-expand" style="box-sizing: border-box;"> (vllm v0.20.2)</span></p><figure class="md-table-fig table-figure md-focus" cid="n1590" mdtype="table" style="box-sizing: border-box; margin: 1.2em 0px; overflow-x: auto; max-width: calc(100% + 16px); padding: 0px; cursor: default; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">
СoncurencyTime (A)Time(T)RPS(A)RPS(T)Mean Latency(A)Mean Latency(T)Max Latency(A)Max Latency(T)Min Latency(A)Min Latency(T)
15.554.890.180.25.094.885.094.885.094.88
521.4420.810.230.2421.1120.7921.1220.821.0920.77
1042.5342.760.240.2342.1942.7142.2142.7442.1642.65
2085.8382.970.230.2485.4382.8985.4882.9685.3682.69
</figure><!--EndFragment--> <!--StartFragment--><!DOCTYPE html><p cid="n1661" mdtype="paragraph" class="md-end-block md-p md-focus" style="box-sizing: border-box; line-height: inherit; orphans: 4; margin: 0.8em 0px; white-space: pre-wrap; position: relative; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><span md-inline="plain" class="md-plain md-expand" style="box-sizing: border-box;"> (vllm v0.21.0)</span></p><figure class="md-table-fig table-figure" cid="n1984" mdtype="table" style="box-sizing: border-box; margin: 1.2em 0px; overflow-x: auto; max-width: calc(100% + 16px); padding: 0px; cursor: default; color: rgb(51, 51, 51); font-family: &quot;Open Sans&quot;, &quot;Clear Sans&quot;, &quot;Helvetica Neue&quot;, Helvetica, Arial, &quot;Segoe UI Emoji&quot;, &quot;SF Pro&quot;, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">
СoncurencyTime (A)Time(T)RPS(A)RPS(T)Mean Latency(A)Mean Latency(T)Max Latency(A)Max Latency(T)Min Latency(A)Min Latency(T)
15.585.060.180.25.095.055.095.055.095.05
521.8621.740.230.2321.4821.7221.4921.7321.4721.7
1043.0342.620.230.2342.6642.5842.6942.6242.6142.52
2085.6285.810.230.2385.2285.7185.2985.7885.1285.6
</figure><!--EndFragment-->

Misc discussion on performance

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Your current environment (if you think it is necessary)

Collecting environment information...

    System Info

============================== OS : Ubuntu 22.04.5 LTS (x86_64) GCC version : (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0 Clang version : Could not collect CMake version : Could not collect Libc version : glibc-2.35

============================== PyTorch Info

PyTorch version : 2.11.0+cu130 Is debug build : False CUDA used to build PyTorch : 13.0 ROCM used to build PyTorch : N/A XPU used to build PyTorch : N/A

============================== Python Environment

Python version : 3.12.13 (main, Mar 4 2026, 09:23:07) [GCC 11.4.0] (64-bit runtime) Python platform : Linux-5.15.0-176-generic-x86_64-with-glibc2.35

============================== CUDA / GPU Info

Is CUDA available : True CUDA runtime version : 13.0.88 CUDA_MODULE_LOADING set to : GPU models and configuration : GPU 0: NVIDIA L40S Nvidia driver version : 570.211.01 cuDNN version : Could not collect HIP runtime version : N/A MIOpen runtime version : N/A Is XNNPACK available : True

============================== CPU Info

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 45 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 24 On-line CPU(s) list: 0-23 Vendor ID: AuthenticAMD Model name: AMD EPYC 9654 96-Core Processor CPU family: 25 Model: 17 Thread(s) per core: 1 Core(s) per socket: 1 Socket(s): 24 Stepping: 1 BogoMIPS: 4792.79 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl tsc_reliable nonstop_tsc cpuid extd_apicid tsc_known_freq pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw topoext invpcid_single ssbd ibrs ibpb ibrs_enhanced vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves avx512_bf16 clzero wbnoinvd arat avx512vbmi umip pku ospke avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid overflow_recov succor fsrm flush_l1d Hypervisor vendor: VMware Virtualization type: full L1d cache: 768 KiB (24 instances) L1i cache: 768 KiB (24 instances) L2 cache: 24 MiB (24 instances) L3 cache: 768 MiB (24 instances) NUMA node(s): 1 NUMA node0 CPU(s): 0-23 Vulnerability Gather data sampling: Not affected Vulnerability Indirect target selection: Not affected Vulnerability Itlb multihit: Not affected Vulnerability L1tf: Not affected Vulnerability Mds: Not affected Vulnerability Meltdown: Not affected Vulnerability Mmio stale data: Not affected Vulnerability Reg file data sampling: Not affected Vulnerability Retbleed: Not affected Vulnerability Spec rstack overflow: Mitigation; safe RET Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Vulnerability Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; STIBP disabled; PBRSB-eIBRS Not affected; BHI Not affected Vulnerability Srbds: Not affected Vulnerability Tsa: Vulnerable: Clear CPU buffers attempted, no microcode Vulnerability Tsx async abort: Not affected Vulnerability Vmscape: Not affected

============================== Versions of relevant libraries

[pip3] flashinfer-python==0.6.8.post1 [pip3] numpy==2.2.6 [pip3] nvidia-cublas==13.1.0.3 [pip3] nvidia-cuda-cupti==13.0.85 [pip3] nvidia-cuda-nvrtc==13.0.88 [pip3] nvidia-cuda-runtime==13.0.96 [pip3] nvidia-cudnn-cu13==9.19.0.56 [pip3] nvidia-cudnn-frontend==1.18.0 [pip3] nvidia-cufft==12.0.0.61 [pip3] nvidia-cufile==1.15.1.6 [pip3] nvidia-curand==10.4.0.35 [pip3] nvidia-cusolver==12.0.4.66 [pip3] nvidia-cusparse==12.6.3.3 [pip3] nvidia-cusparselt-cu13==0.8.0 [pip3] nvidia-cutlass-dsl==4.4.2 [pip3] nvidia-cutlass-dsl-libs-base==4.4.2 [pip3] nvidia-ml-py==13.595.45 [pip3] nvidia-nccl-cu13==2.28.9 [pip3] nvidia-nvjitlink==13.0.88 [pip3] nvidia-nvshmem-cu13==3.4.5 [pip3] nvidia-nvtx==13.0.85 [pip3] pyzmq==27.1.0 [pip3] tokenspeed-triton==3.7.10.post20260505 [pip3] torch==2.11.0+cu130 [pip3] torch_c_dlpack_ext==0.1.5 [pip3] torchaudio==2.11.0+cu130 [pip3] torchvision==0.26.0+cu130 [pip3] transformers==5.8.1 [pip3] triton==3.6.0 [conda] Could not collect

============================== vLLM Info

ROCM Version : Could not collect vLLM Version : 0.21.0 vLLM Build Flags: CUDA Archs: 7.5 8.0 8.6 8.9 9.0 10.0 12.0+PTX; ROCm: Disabled; XPU: Disabled GPU Topology: GPU0 CPU Affinity NUMA Affinity GPU NUMA ID GPU0 X 0-23 0 N/A

Legend:

X = Self SYS = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI) NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node PHB = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU) PXB = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge) PIX = Connection traversing at most a single PCIe bridge NV# = Connection traversing a bonded set of # NVLinks

============================== Environment Variables

NVIDIA_VISIBLE_DEVICES=all NVIDIA_REQUIRE_CUDA=cuda>=13.0 brand=unknown,driver>=535,driver<536 brand=grid,driver>=535,driver<536 brand=tesla,driver>=535,driver<536 brand=nvidia,driver>=535,driver<536 brand=quadro,driver>=535,driver<536 brand=quadrortx,driver>=535,driver<536 brand=nvidiartx,driver>=535,driver<536 brand=vapps,driver>=535,driver<536 brand=vpc,driver>=535,driver<536 brand=vcs,driver>=535,driver<536 brand=vws,driver>=535,driver<536 brand=cloudgaming,driver>=535,driver<536 brand=unknown,driver>=550,driver<551 brand=grid,driver>=550,driver<551 brand=tesla,driver>=550,driver<551 brand=nvidia,driver>=550,driver<551 brand=quadro,driver>=550,driver<551 brand=quadrortx,driver>=550,driver<551 brand=nvidiartx,driver>=550,driver<551 brand=vapps,driver>=550,driver<551 brand=vpc,driver>=550,driver<551 brand=vcs,driver>=550,driver<551 brand=vws,driver>=550,driver<551 brand=cloudgaming,driver>=550,driver<551 brand=unknown,driver>=565,driver<566 brand=grid,driver>=565,driver<566 brand=tesla,driver>=565,driver<566 brand=nvidia,driver>=565,driver<566 brand=quadro,driver>=565,driver<566 brand=quadrortx,driver>=565,driver<566 brand=nvidiartx,driver>=565,driver<566 brand=vapps,driver>=565,driver<566 brand=vpc,driver>=565,driver<566 brand=vcs,driver>=565,driver<566 brand=vws,driver>=565,driver<566 brand=cloudgaming,driver>=565,driver<566 brand=unknown,driver>=570,driver<571 brand=grid,driver>=570,driver<571 brand=tesla,driver>=570,driver<571 brand=nvidia,driver>=570,driver<571 brand=quadro,driver>=570,driver<571 brand=quadrortx,driver>=570,driver<571 brand=nvidiartx,driver>=570,driver<571 brand=vapps,driver>=570,driver<571 brand=vpc,driver>=570,driver<571 brand=vcs,driver>=570,driver<571 brand=vws,driver>=570,driver<571 brand=cloudgaming,driver>=570,driver<571 brand=unknown,driver>=575,driver<576 brand=grid,driver>=575,driver<576 brand=tesla,driver>=575,driver<576 brand=nvidia,driver>=575,driver<576 brand=quadro,driver>=575,driver<576 brand=quadrortx,driver>=575,driver<576 brand=nvidiartx,driver>=575,driver<576 brand=vapps,driver>=575,driver<576 brand=vpc,driver>=575,driver<576 brand=vcs,driver>=575,driver<576 brand=vws,driver>=575,driver<576 brand=cloudgaming,driver>=575,driver<576 TORCH_CUDA_ARCH_LIST=7.5 8.0 8.6 8.9 9.0 10.0 12.0+PTX NVIDIA_DRIVER_CAPABILITIES=compute,utility VLLM_USAGE_SOURCE=production-docker-image CUDA_VERSION=13.0.2 VLLM_ENABLE_CUDA_COMPATIBILITY=0 LD_LIBRARY_PATH=/usr/local/nvidia/lib64:/usr/local/cuda/lib64:/usr/local/nvidia/lib:/usr/local/nvidia/lib64:/usr/local/cuda/lib64 VLLM_LOGGING_LEVEL=DEBUG PYTORCH_NVML_BASED_CUDA_CHECK=1 TORCHINDUCTOR_COMPILE_THREADS=1 TORCHINDUCTOR_CACHE_DIR=/tmp/torchinductor_root

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vllm - 💡(How to fix) Fix [Performance]: Significant performance degradation v1/reranker under concurrent requests while swiching from v.0.19.1 to v0.20.2 v0.21.1