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Eval bug: Server Returns Empty Responses Under High Load #13703

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@prd-tuong-nguyen

Description

@prd-tuong-nguyen

Name and Version

Image: https://github.com/ggml-org/llama.cpp/pkgs/container/llama.cpp/421179669?tag=server-cuda-b5452

Operating systems

Linux

GGML backends

CUDA

Hardware

L40S GPU (aws g6e.xlarge instance)

Models

https://huggingface.co/lmstudio-community/gemma-3-27b-it-GGUF/resolve/main/gemma-3-27b-it-Q4_K_M.gguf

Problem description & steps to reproduce

Command: docker run -p 8080:8080 -it --gpus all ghcr.io/ggml-org/llama.cpp:server-cuda --port 8080 --host 0.0.0.0 --parallel 16 --ctx-size 49152 --cont-batching --slot-prompt-similarity 0.3 --n-gpu-layers 100000000 --flash-attn --no-warmup --jinja --lora-init-without-apply --lora-scaled ... -m ...
After the high-load requests (50 CCU), the server response empty content even the completion_tokens is ok
This is the difference in log:
The error version:

llama_kv_cache_unified_iswa: creating non-SWA KV cache, size = 49152 cells
llama_kv_cache_unified:      CUDA0 KV buffer size =  3840.00 MiB
llama_kv_cache_unified: size = 3840.00 MiB ( 49152 cells,  10 layers), K (f16): 1920.00 MiB, V (f16): 1920.00 MiB
llama_kv_cache_unified_iswa: creating     SWA KV cache, size = 18432 cells
llama_kv_cache_unified:      CUDA0 KV buffer size =  7488.00 MiB
llama_kv_cache_unified: size = 7488.00 MiB ( 18432 cells,  52 layers), K (f16): 3744.00 MiB, V (f16): 3744.00 MiB
llama_context:      CUDA0 compute buffer size =   130.62 MiB
llama_context:  CUDA_Host compute buffer size =    35.63 MiB
llama_context: graph nodes  = 2489
llama_context: graph splits = 2
common_init_from_params: KV cache shifting is not supported for this context, disabling KV cache shifting

The previous version (work well):

llama_kv_cache_unified: kv_size = 49152, type_k = 'f16', type_v = 'f16', n_layer = 62, can_shift = 1, padding = 256
llama_kv_cache_unified:      CUDA0 KV buffer size = 23808.00 MiB
llama_kv_cache_unified: KV self size  = 23808.00 MiB, K (f16): 11904.00 MiB, V (f16): 11904.00 MiB
llama_context:      CUDA0 compute buffer size =   522.50 MiB
llama_context:  CUDA_Host compute buffer size =   202.51 MiB
llama_context: graph nodes  = 2365
llama_context: graph splits = 2

Example response error:

{
    "id": "chatcmpl-lck9Lm6T24oN61ZuwgXtfzWxYBLhKzkO",
    "created": 1747909068,
    "model": "google/gemma-3-27b-it",
    "object": "chat.completion",
    "system_fingerprint": "b5428-f0adb80b",
    "choices": [
        {
            "finish_reason": "length",
            "index": 0,
            "message": {
                "content": "l",
                "role": "assistant",
                "tool_calls": null,
                "function_call": null,
                "refusal": null
            }
        }
    ],
    "usage": {
        "completion_tokens": 45,
        "prompt_tokens": 630,
        "total_tokens": 675,
        "completion_tokens_details": null,
        "prompt_tokens_details": null
    },
    "service_tier": null,
    "timings": {
        "prompt_n": 630,
        "prompt_ms": 430.044,
        "prompt_per_token_ms": 0.6826095238095238,
        "prompt_per_second": 1464.9663755336665,
        "predicted_n": 45,
        "predicted_ms": 1818.511,
        "predicted_per_token_ms": 40.41135555555555,
        "predicted_per_second": 24.74551982363593
    }
}

First Bad Commit

This image is still working fine: https://github.com/ggml-org/llama.cpp/pkgs/container/llama.cpp/419241486?tag=server-cuda-b5428

Relevant log output

ggml_cuda_init: GGML_CUDA_FORCE_MMQ:    no
ggml_cuda_init: GGML_CUDA_FORCE_CUBLAS: no
ggml_cuda_init: found 1 CUDA devices:
  Device 0: NVIDIA L40S, compute capability 8.9, VMM: yes
load_backend: loaded CUDA backend from /app/libggml-cuda.so
load_backend: loaded CPU backend from /app/libggml-cpu-haswell.so
warn: LLAMA_ARG_HOST environment variable is set, but will be overwritten by command line argument --host
build: 5439 (33983057) with cc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0 for x86_64-linux-gnu
system info: n_threads = 2, n_threads_batch = 2, total_threads = 4

system_info: n_threads = 2 (n_threads_batch = 2) / 4 | CUDA : ARCHS = 500,610,700,750,800,860,890 | USE_GRAPHS = 1 | PEER_MAX_BATCH_SIZE = 128 | CPU : SSE3 = 1 | SSSE3 = 1 | AVX = 1 | AVX2 = 1 | F16C = 1 | FMA = 1 | BMI2 = 1 | LLAMAFILE = 1 | OPENMP = 1 | AARCH64_REPACK = 1 | 

main: binding port with default address family
main: HTTP server is listening, hostname: 0.0.0.0, port: 8080, http threads: 18
main: loading model
srv    load_model: loading model '/models/gemma-3-27b-it-Q4_K_M.gguf'
llama_model_load_from_file_impl: using device CUDA0 (NVIDIA L40S) - 45036 MiB free
llama_model_loader: loaded meta data with 40 key-value pairs and 808 tensors from /models/gemma-3-27b-it-Q4_K_M.gguf (version GGUF V3 (latest))
llama_model_loader: Dumping metadata keys/values. Note: KV overrides do not apply in this output.
llama_model_loader: - kv   0:                       general.architecture str              = gemma3
llama_model_loader: - kv   1:                               general.type str              = model
llama_model_loader: - kv   2:                               general.name str              = Gemma 3 27b It
llama_model_loader: - kv   3:                           general.finetune str              = it
llama_model_loader: - kv   4:                           general.basename str              = gemma-3
llama_model_loader: - kv   5:                         general.size_label str              = 27B
llama_model_loader: - kv   6:                            general.license str              = gemma
llama_model_loader: - kv   7:                   general.base_model.count u32              = 1
llama_model_loader: - kv   8:                  general.base_model.0.name str              = Gemma 3 27b Pt
llama_model_loader: - kv   9:          general.base_model.0.organization str              = Google
llama_model_loader: - kv  10:              general.base_model.0.repo_url str              = https://huggingface.co/google/gemma-3...
llama_model_loader: - kv  11:                               general.tags arr[str,1]       = ["image-text-to-text"]
llama_model_loader: - kv  12:                      gemma3.context_length u32              = 131072
llama_model_loader: - kv  13:                    gemma3.embedding_length u32              = 5376
llama_model_loader: - kv  14:                         gemma3.block_count u32              = 62
llama_model_loader: - kv  15:                 gemma3.feed_forward_length u32              = 21504
llama_model_loader: - kv  16:                gemma3.attention.head_count u32              = 32
llama_model_loader: - kv  17:    gemma3.attention.layer_norm_rms_epsilon f32              = 0.000001
llama_model_loader: - kv  18:                gemma3.attention.key_length u32              = 128
llama_model_loader: - kv  19:              gemma3.attention.value_length u32              = 128
llama_model_loader: - kv  20:                      gemma3.rope.freq_base f32              = 1000000.000000
llama_model_loader: - kv  21:            gemma3.attention.sliding_window u32              = 1024
llama_model_loader: - kv  22:             gemma3.attention.head_count_kv u32              = 16
llama_model_loader: - kv  23:                   gemma3.rope.scaling.type str              = linear
llama_model_loader: - kv  24:                 gemma3.rope.scaling.factor f32              = 8.000000
llama_model_loader: - kv  25:                       tokenizer.ggml.model str              = llama
llama_model_loader: - kv  26:                         tokenizer.ggml.pre str              = default
llama_model_loader: - kv  27:                      tokenizer.ggml.tokens arr[str,262144]  = ["<pad>", "<eos>", "<bos>", "<unk>", ...
llama_model_loader: - kv  28:                      tokenizer.ggml.scores arr[f32,262144]  = [-1000.000000, -1000.000000, -1000.00...
llama_model_loader: - kv  29:                  tokenizer.ggml.token_type arr[i32,262144]  = [3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 3, ...
llama_model_loader: - kv  30:                tokenizer.ggml.bos_token_id u32              = 2
llama_model_loader: - kv  31:                tokenizer.ggml.eos_token_id u32              = 1
llama_model_loader: - kv  32:            tokenizer.ggml.unknown_token_id u32              = 3
llama_model_loader: - kv  33:            tokenizer.ggml.padding_token_id u32              = 0
llama_model_loader: - kv  34:               tokenizer.ggml.add_bos_token bool             = true
llama_model_loader: - kv  35:               tokenizer.ggml.add_eos_token bool             = false
llama_model_loader: - kv  36:                    tokenizer.chat_template str              = {{ bos_token }}\n{%- if messages[0]['r...
llama_model_loader: - kv  37:            tokenizer.ggml.add_space_prefix bool             = false
llama_model_loader: - kv  38:               general.quantization_version u32              = 2
llama_model_loader: - kv  39:                          general.file_type u32              = 15
llama_model_loader: - type  f32:  373 tensors
llama_model_loader: - type q4_K:  374 tensors
llama_model_loader: - type q6_K:   61 tensors
print_info: file format = GGUF V3 (latest)
print_info: file type   = Q4_K - Medium
print_info: file size   = 15.40 GiB (4.90 BPW) 
load: special_eos_id is not in special_eog_ids - the tokenizer config may be incorrect
load: special tokens cache size = 6414
load: token to piece cache size = 1.9446 MB
print_info: arch             = gemma3
print_info: vocab_only       = 0
print_info: n_ctx_train      = 131072
print_info: n_embd           = 5376
print_info: n_layer          = 62
print_info: n_head           = 32
print_info: n_head_kv        = 16
print_info: n_rot            = 128
print_info: n_swa            = 1024
print_info: n_swa_pattern    = 6
print_info: n_embd_head_k    = 128
print_info: n_embd_head_v    = 128
print_info: n_gqa            = 2
print_info: n_embd_k_gqa     = 2048
print_info: n_embd_v_gqa     = 2048
print_info: f_norm_eps       = 0.0e+00
print_info: f_norm_rms_eps   = 1.0e-06
print_info: f_clamp_kqv      = 0.0e+00
print_info: f_max_alibi_bias = 0.0e+00
print_info: f_logit_scale    = 0.0e+00
print_info: f_attn_scale     = 7.7e-02
print_info: n_ff             = 21504
print_info: n_expert         = 0
print_info: n_expert_used    = 0
print_info: causal attn      = 1
print_info: pooling type     = 0
print_info: rope type        = 2
print_info: rope scaling     = linear
print_info: freq_base_train  = 1000000.0
print_info: freq_scale_train = 0.125
print_info: n_ctx_orig_yarn  = 131072
print_info: rope_finetuned   = unknown
print_info: ssm_d_conv       = 0
print_info: ssm_d_inner      = 0
print_info: ssm_d_state      = 0
print_info: ssm_dt_rank      = 0
print_info: ssm_dt_b_c_rms   = 0
print_info: model type       = 27B
print_info: model params     = 27.01 B
print_info: general.name     = Gemma 3 27b It
print_info: vocab type       = SPM
print_info: n_vocab          = 262144
print_info: n_merges         = 0
print_info: BOS token        = 2 '<bos>'
print_info: EOS token        = 1 '<eos>'
print_info: EOT token        = 106 '<end_of_turn>'
print_info: UNK token        = 3 '<unk>'
print_info: PAD token        = 0 '<pad>'
print_info: LF token         = 248 '<0x0A>'
print_info: EOG token        = 1 '<eos>'
print_info: EOG token        = 106 '<end_of_turn>'
print_info: max token length = 48
load_tensors: loading model tensors, this can take a while... (mmap = true)
load_tensors: offloading 62 repeating layers to GPU
load_tensors: offloading output layer to GPU
load_tensors: offloaded 63/63 layers to GPU
load_tensors:        CUDA0 model buffer size = 15773.70 MiB
load_tensors:   CPU_Mapped model buffer size =  1102.50 MiB
.........................................................................................
llama_context: constructing llama_context
llama_context: n_seq_max     = 16
llama_context: n_ctx         = 49152
llama_context: n_ctx_per_seq = 3072
llama_context: n_batch       = 2048
llama_context: n_ubatch      = 128
llama_context: causal_attn   = 1
llama_context: flash_attn    = 1
llama_context: freq_base     = 1000000.0
llama_context: freq_scale    = 0.125
llama_context: n_ctx_per_seq (3072) < n_ctx_train (131072) -- the full capacity of the model will not be utilized
llama_context:  CUDA_Host  output buffer size =    16.00 MiB
llama_kv_cache_unified_iswa: creating non-SWA KV cache, size = 49152 cells
llama_kv_cache_unified:      CUDA0 KV buffer size =  3840.00 MiB
llama_kv_cache_unified: size = 3840.00 MiB ( 49152 cells,  10 layers), K (f16): 1920.00 MiB, V (f16): 1920.00 MiB
llama_kv_cache_unified_iswa: creating     SWA KV cache, size = 18432 cells
llama_kv_cache_unified:      CUDA0 KV buffer size =  7488.00 MiB
llama_kv_cache_unified: size = 7488.00 MiB ( 18432 cells,  52 layers), K (f16): 3744.00 MiB, V (f16): 3744.00 MiB
llama_context:      CUDA0 compute buffer size =   130.62 MiB
llama_context:  CUDA_Host compute buffer size =    35.63 MiB
llama_context: graph nodes  = 2489
llama_context: graph splits = 2
common_init_from_params: KV cache shifting is not supported for this context, disabling KV cache shifting
llama_adapter_lora_init_impl: loading lora adapter from '/models/adapters/care_augment_river_v0.1.31.gguf' ...
llama_adapter_lora_init_impl:      CUDA0 LoRA buffer size =   433.03 MiB
llama_adapter_lora_init_impl: loaded 868 tensors from lora file
common_init_from_params: setting dry_penalty_last_n to ctx_size = 49152
srv          init: initializing slots, n_slots = 16
slot         init: id  0 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  1 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  2 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  3 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  4 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  5 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  6 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  7 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  8 | task -1 | new slot n_ctx_slot = 3072
slot         init: id  9 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 10 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 11 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 12 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 13 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 14 | task -1 | new slot n_ctx_slot = 3072
slot         init: id 15 | task -1 | new slot n_ctx_slot = 3072
main: model loaded
main: chat template, chat_template: {{ bos_token }}
{%- if messages[0]['role'] == 'system' -%}
    {%- if messages[0]['content'] is string -%}
        {%- set first_user_prefix = messages[0]['content'] + '

' -%}
    {%- else -%}
        {%- set first_user_prefix = messages[0]['content'][0]['text'] + '

' -%}
    {%- endif -%}
    {%- set loop_messages = messages[1:] -%}
{%- else -%}
    {%- set first_user_prefix = "" -%}
    {%- set loop_messages = messages -%}
{%- endif -%}
{%- for message in loop_messages -%}
    {%- if (message['role'] == 'user') != (loop.index0 % 2 == 0) -%}
        {{ raise_exception("Conversation roles must alternate user/assistant/user/assistant/...") }}
    {%- endif -%}
    {%- if (message['role'] == 'assistant') -%}
        {%- set role = "model" -%}
    {%- else -%}
        {%- set role = message['role'] -%}
    {%- endif -%}
    {{ '<start_of_turn>' + role + '
' + (first_user_prefix if loop.first else "") }}
    {%- if message['content'] is string -%}
        {{ message['content'] | trim }}
    {%- elif message['content'] is iterable -%}
        {%- for item in message['content'] -%}
            {%- if item['type'] == 'image' -%}
                {{ '<start_of_image>' }}
            {%- elif item['type'] == 'text' -%}
                {{ item['text'] | trim }}
            {%- endif -%}
        {%- endfor -%}
    {%- else -%}
        {{ raise_exception("Invalid content type") }}
    {%- endif -%}
    {{ '<end_of_turn>
' }}
{%- endfor -%}
{%- if add_generation_prompt -%}
    {{'<start_of_turn>model
'}}
{%- endif -%}
, example_format: '<start_of_turn>user
You are a helpful assistant

Hello<end_of_turn>
<start_of_turn>model
Hi there<end_of_turn>
<start_of_turn>user
How are you?<end_of_turn>
<start_of_turn>model
'
main: server is listening on http://0.0.0.0:8080 - starting the main loop

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