[Bug]: assert total_num_scheduled_tokens > 0

[sakunkun]

Your current environment

The output of `python collect_env.py`

Collecting environment information...
PyTorch version: 2.5.1+cu124
Is debug build: False
CUDA used to build PyTorch: 12.4
ROCM used to build PyTorch: N/A

OS: Ubuntu 22.04.3 LTS (x86_64)
GCC version: (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Clang version: Could not collect
CMake version: Could not collect
Libc version: glibc-2.35

Python version: 3.12.8 (main, Dec  4 2024, 08:54:12) [GCC 11.4.0] (64-bit runtime)
Python platform: Linux-6.8.0-41-generic-x86_64-with-glibc2.35
Is CUDA available: True
CUDA runtime version: Could not collect
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration: 
GPU 0: NVIDIA L40S
GPU 1: NVIDIA L40S
GPU 2: NVIDIA L40S
GPU 3: NVIDIA L40S

Nvidia driver version: 535.154.05
cuDNN version: Could not collect
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Architecture:                         x86_64
CPU op-mode(s):                       32-bit, 64-bit
Address sizes:                        46 bits physical, 57 bits virtual
Byte Order:                           Little Endian
CPU(s):                               128
On-line CPU(s) list:                  0-127
Vendor ID:                            GenuineIntel
BIOS Vendor ID:                       Intel(R) Corporation
Model name:                           Intel(R) Xeon(R) Gold 6430
BIOS Model name:                      Intel(R) Xeon(R) Gold 6430
CPU family:                           6
Model:                                143
Thread(s) per core:                   2
Core(s) per socket:                   32
Socket(s):                            2
Stepping:                             8
CPU max MHz:                          3400.0000
CPU min MHz:                          800.0000
BogoMIPS:                             4200.00
Flags:                                fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cat_l2 cdp_l3 intel_ppin cdp_l2 ssbd mba ibrs ibpb stibp ibrs_enhanced tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb intel_pt avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local split_lock_detect user_shstk avx_vnni avx512_bf16 wbnoinvd dtherm ida arat pln pts hwp hwp_act_window hwp_epp hwp_pkg_req vnmi avx512vbmi umip pku ospke waitpkg avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg tme avx512_vpopcntdq la57 rdpid bus_lock_detect cldemote movdiri movdir64b enqcmd fsrm md_clear serialize tsxldtrk pconfig arch_lbr ibt amx_bf16 avx512_fp16 amx_tile amx_int8 flush_l1d arch_capabilities
Virtualization:                       VT-x
L1d cache:                            3 MiB (64 instances)
L1i cache:                            2 MiB (64 instances)
L2 cache:                             128 MiB (64 instances)
L3 cache:                             120 MiB (2 instances)
NUMA node(s):                         2
NUMA node0 CPU(s):                    0-31,64-95
NUMA node1 CPU(s):                    32-63,96-127
Vulnerability Gather data sampling:   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:   Not affected
Vulnerability Spec store bypass:      Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:             Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:             Mitigation; Enhanced / Automatic IBRS; IBPB conditional; RSB filling; PBRSB-eIBRS SW sequence; BHI BHI_DIS_S
Vulnerability Srbds:                  Not affected
Vulnerability Tsx async abort:        Not affected

Versions of relevant libraries:
[pip3] flashinfer==0.1.6+cu121torch2.4
[pip3] numpy==1.26.4
[pip3] nvidia-cublas-cu12==12.4.5.8
[pip3] nvidia-cuda-cupti-cu12==12.4.127
[pip3] nvidia-cuda-nvrtc-cu12==12.4.127
[pip3] nvidia-cuda-runtime-cu12==12.4.127
[pip3] nvidia-cudnn-cu12==9.1.0.70
[pip3] nvidia-cufft-cu12==11.2.1.3
[pip3] nvidia-curand-cu12==10.3.5.147
[pip3] nvidia-cusolver-cu12==11.6.1.9
[pip3] nvidia-cusparse-cu12==12.3.1.170
[pip3] nvidia-ml-py==12.560.30
[pip3] nvidia-nccl-cu12==2.21.5
[pip3] nvidia-nvjitlink-cu12==12.4.127
[pip3] nvidia-nvtx-cu12==12.4.127
[pip3] pyzmq==26.2.0
[pip3] torch==2.5.1
[pip3] torchvision==0.20.1
[pip3] transformers==4.47.1
[pip3] triton==3.1.0
[conda] Could not collect
ROCM Version: Could not collect
Neuron SDK Version: N/A
vLLM Version: 0.6.5
vLLM Build Flags:
CUDA Archs: Not Set; ROCm: Disabled; Neuron: Disabled
GPU Topology:
GPU0    GPU1    GPU2    GPU3    NIC0    NIC1    NIC2    NIC3    NIC4    NIC5    NIC6    NIC7    NIC8    NIC9    NIC10     NIC11   NIC12   NIC13   NIC14   NIC15   NIC16   NIC17   NIC18   NIC19   NIC20   NIC21   NIC22   NIC23   NIC24     NIC25   CPU Affinity    NUMA Affinity   GPU NUMA ID
GPU0     X      SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     0-31,64-95      0               N/A
GPU1    SYS      X      SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     0-31,64-95      0               N/A
GPU2    SYS     SYS      X      SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     32-63,96-127    1               N/A
GPU3    SYS     SYS     SYS      X      SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     32-63,96-127    1               N/A
NIC0    SYS     SYS     SYS     SYS      X      PIX     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC1    SYS     SYS     SYS     SYS     PIX      X      SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC2    SYS     SYS     SYS     SYS     SYS     SYS      X      PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC3    SYS     SYS     SYS     SYS     SYS     SYS     PIX      X      SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC4    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS      X      PIX     SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC5    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     PIX      X      SYS     SYS     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC6    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS      X      PIX     SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC7    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     PIX      X      SYS     SYS       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC8    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS      X      PIX       SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC9    SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     PIX      X        SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS     SYS       SYS     SYS
NIC10   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS        X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC11   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC12   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC13   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC14   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC15   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC16   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC17   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC18   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX     PIX       PIX     PIX
NIC19   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX     PIX       PIX     PIX
NIC20   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX     PIX       PIX     PIX
NIC21   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX     PIX       PIX     PIX
NIC22   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X      PIX       PIX     PIX
NIC23   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX      X        PIX     PIX
NIC24   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX        X      PIX
NIC25   SYS     SYS     SYS     SYS     SYS     SYS     PIX     PIX     SYS     SYS     SYS     SYS     SYS     SYS       PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX     PIX       PIX      X 

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

NIC Legend:

  NIC0: mlx5_0
  NIC1: mlx5_1
  NIC2: mlx5_2
  NIC3: mlx5_3
  NIC4: mlx5_4
  NIC5: mlx5_5
  NIC6: mlx5_6
  NIC7: mlx5_7
  NIC8: mlx5_8
  NIC9: mlx5_9
  NIC10: mlx5_10
  NIC11: mlx5_11
  NIC12: mlx5_12
  NIC13: mlx5_13
  NIC14: mlx5_14
  NIC15: mlx5_15
  NIC16: mlx5_16
  NIC17: mlx5_17
  NIC18: mlx5_18
  NIC19: mlx5_19
  NIC20: mlx5_20
  NIC21: mlx5_21
  NIC22: mlx5_22
  NIC23: mlx5_23
  NIC24: mlx5_24
  NIC25: mlx5_25

NVIDIA_VISIBLE_DEVICES=all
NVIDIA_REQUIRE_CUDA=cuda>=12.1 brand=tesla,driver>=470,driver<471 brand=unknown,driver>=470,driver<471 brand=nvidia,driver>=470,driver<471 brand=nvidiartx,driver>=470,driver<471 brand=geforce,driver>=470,driver<471 brand=geforcertx,driver>=470,driver<471 brand=quadro,driver>=470,driver<471 brand=quadrortx,driver>=470,driver<471 brand=titan,driver>=470,driver<471 brand=titanrtx,driver>=470,driver<471 brand=tesla,driver>=525,driver<526 brand=unknown,driver>=525,driver<526 brand=nvidia,driver>=525,driver<526 brand=nvidiartx,driver>=525,driver<526 brand=geforce,driver>=525,driver<526 brand=geforcertx,driver>=525,driver<526 brand=quadro,driver>=525,driver<526 brand=quadrortx,driver>=525,driver<526 brand=titan,driver>=525,driver<526 brand=titanrtx,driver>=525,driver<526
NVIDIA_DRIVER_CAPABILITIES=compute,utility
VLLM_USAGE_SOURCE=production-docker-image
CUDA_VERSION=12.1.0
LD_LIBRARY_PATH=/usr/local/lib/python3.12/dist-packages/cv2/../../lib64:/usr/local/nvidia/lib:/usr/local/nvidia/lib64
VLLM_USE_V1=1
CUDA_MODULE_LOADING=LAZY

Model Input Dumps

No response

🐛 Describe the bug

When V1 and prefix_caching are enabled, when allocating slots for requests in the waiting queue, the function immediately _touch(computed_blocks) at the beginning, incrementing their ref_cnt by 1. If free_block_queue.num_free_blocks is insufficient to allocate new blocks, the function returns None, causing the scheduling loop to break directly. At this point, the request remains in the waiting queue, but the ref_cnt of all blocks in computed_blocks has been incremented. This situation recurs, eventually leading to some blocks having a ref_cnt greater than 0 even though no request is using them.

# ===============scheduler
request = self.waiting[0]
computed_blocks = self.kv_cache_manager.get_computed_blocks(
    request)
......
new_blocks = self.kv_cache_manager.allocate_slots(
    request, num_new_tokens, computed_blocks)
if new_blocks is None:
    break

self.waiting.popleft()

#================kv_cache_manager
   def allocate_slots(
        self,
        request: Request,
        num_tokens: int,
        computed_blocks: List[KVCacheBlock],
    ) -> Optional[List[KVCacheBlock]]:
        """Allocate slots for a new request.

        Args:
            request: The request to allocate slots.
            num_tokens: The number of tokens to allocate. Note that this does
                not include the tokens that have already been computed.
            computed_blocks: The blocks that have already been computed.

        Returns:
            A list of new allocated blocks.
        """
        if num_tokens == 0:
            raise ValueError(
                f"num_tokens must be greater than 0, got {num_tokens}")

        # Touch the computed blocks to make sure they won't be evicted.
        num_evictable_computed_blocks = 0
        if self.enable_caching:
            self._touch(computed_blocks)

            # If a computed block of a request is an eviction candidate (in the
            # free queue and ref_cnt == 0), it cannot be counted as a free block
            # when allocating this request.
            num_evictable_computed_blocks = len(
                [blk for blk in computed_blocks if blk.ref_cnt == 0])
        else:
            assert not computed_blocks, (
                "Computed blocks should be empty when "
                "prefix caching is disabled")

        num_required_blocks = cdiv(num_tokens, self.block_size)
        if (num_required_blocks > self.free_block_queue.num_free_blocks -
                num_evictable_computed_blocks):
            # Cannot allocate new blocks.
            return None

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