Repository: ggml-org/llama.cpp
Pull request: vulkan: enable mmvq for q2_k on NVIDIA

See https://github.com/ggml-org/llama.cpp/pull/16900#issuecomment-3590059550.

```
before:

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -fa 1 -n 128 -p 0 -r 10 --prio 1 -m c:\models\Llama-3.2-1B.Q2_K.gguf -m c:\models\Qwen_Qwen3-30B-A3B-Q2_K.gguf -m c:\models\Qwen2.5-7B-Instruct-1M-Q2_K.gguf
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 5090 (NVIDIA) | uma: 0 | fp16: 1 | bf16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |            test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | --------------: | -------------------: |
| llama 1B Q2_K - Medium         | 546.50 MiB |     1.24 B | Vulkan     |  99 |  1 |           tg128 |        947.00 ± 9.72 |
| qwen3moe 30B.A3B Q2_K - Medium |  10.15 GiB |    30.53 B | Vulkan     |  99 |  1 |           tg128 |        310.39 ± 5.99 |
| qwen2 7B Q2_K - Medium         |   2.80 GiB |     7.62 B | Vulkan     |  99 |  1 |           tg128 |        273.41 ± 3.16 |

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -fa 1 -n 128 -p 0 -r 10 --prio 1 -m c:\models\Llama-3.2-1B.Q2_K.gguf -m c:\models\Qwen_Qwen3-30B-A3B-Q2_K.gguf -m c:\models\Qwen2.5-7B-Instruct-1M-Q2_K.gguf
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 4070 (NVIDIA) | uma: 0 | fp16: 1 | bf16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |            test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | --------------: | -------------------: |
| llama 1B Q2_K - Medium         | 546.50 MiB |     1.24 B | Vulkan     |  99 |  1 |           tg128 |        474.11 ± 6.99 |
| qwen3moe 30B.A3B Q2_K - Medium |  10.15 GiB |    30.53 B | Vulkan     |  99 |  1 |           tg128 |        163.50 ± 8.40 |
| qwen2 7B Q2_K - Medium         |   2.80 GiB |     7.62 B | Vulkan     |  99 |  1 |           tg128 |        109.54 ± 0.35 |

after:

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -fa 1 -n 128 -p 0 -r 10 --prio 1 -m c:\models\Llama-3.2-1B.Q2_K.gguf -m c:\models\Qwen_Qwen3-30B-A3B-Q2_K.gguf -m c:\models\Qwen2.5-7B-Instruct-1M-Q2_K.gguf
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 5090 (NVIDIA) | uma: 0 | fp16: 1 | bf16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |            test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | --------------: | -------------------: |
| llama 1B Q2_K - Medium         | 546.50 MiB |     1.24 B | Vulkan     |  99 |  1 |           tg128 |       1006.78 ± 5.04 |
| qwen3moe 30B.A3B Q2_K - Medium |  10.15 GiB |    30.53 B | Vulkan     |  99 |  1 |           tg128 |        321.59 ± 6.88 |
| qwen2 7B Q2_K - Medium         |   2.80 GiB |     7.62 B | Vulkan     |  99 |  1 |           tg128 |       308.31 ± 15.10 |

Z:\github\jeffbolznv\llama.cpp\build\bin\RelWithDebInfo>llama-bench.exe -fa 1 -n 128 -p 0 -r 10 --prio 1 -m c:\models\Llama-3.2-1B.Q2_K.gguf -m c:\models\Qwen_Qwen3-30B-A3B-Q2_K.gguf -m c:\models\Qwen2.5-7B-Instruct-1M-Q2_K.gguf
ggml_vulkan: Found 1 Vulkan devices:
ggml_vulkan: 0 = NVIDIA GeForce RTX 4070 (NVIDIA) | uma: 0 | fp16: 1 | bf16: 1 | warp size: 32 | shared memory: 49152 | int dot: 1 | matrix cores: NV_coopmat2
| model                          |       size |     params | backend    | ngl | fa |            test |                  t/s |
| ------------------------------ | ---------: | ---------: | ---------- | --: | -: | --------------: | -------------------: |
| llama 1B Q2_K - Medium         | 546.50 MiB |     1.24 B | Vulkan     |  99 |  1 |           tg128 |        524.19 ± 3.78 |
| qwen3moe 30B.A3B Q2_K - Medium |  10.15 GiB |    30.53 B | Vulkan     |  99 |  1 |           tg128 |        183.29 ± 9.55 |
| qwen2 7B Q2_K - Medium         |   2.80 GiB |     7.62 B | Vulkan     |  99 |  1 |           tg128 |        124.85 ± 0.24 |
```

Changed files:
filename: ggml/src/ggml-vulkan/ggml-vulkan.cpp
patch: @@ -6948,6 +6948,10 @@ static bool ggml_vk_should_use_mmvq(const vk_device& device, uint32_t m, uint32_
     // Quantization overhead is not worth it for small k
     switch (device->vendor_id) {
     case VK_VENDOR_ID_NVIDIA:
+        if (src0_type == GGML_TYPE_Q2_K) {
+            return true;
+        }
+
         if (k <= 4096) {
             return false;
         }