From: Jeff Bolz <redacted>
Date: Thu, 5 Feb 2026 07:48:33 +0000 (-0600)
Subject: vulkan: Set k_load_shmem to false when K is too large (#19301)
X-Git-Tag: upstream/0.0.8067~123
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=3409ab842d988c3e0dc0d3110dd793a5e187d37e;p=pkg%2Fggml%2Fsources%2Fllama.cpp

vulkan: Set k_load_shmem to false when K is too large (#19301)
---

diff --git a/ggml/src/ggml-vulkan/ggml-vulkan.cpp b/ggml/src/ggml-vulkan/ggml-vulkan.cpp
index af57685a3..2f6570181 100644
--- a/ggml/src/ggml-vulkan/ggml-vulkan.cpp
+++ b/ggml/src/ggml-vulkan/ggml-vulkan.cpp
@@ -3204,9 +3204,10 @@ static void ggml_vk_load_shaders(vk_device& device) {
         const uint32_t D_lsb = D ^ (D & (D-1));
         uint32_t D_split = std::min(std::min(device->subgroup_size, 8u), D_lsb / 4);
 
-        // Nvidia prefers shared memory use to load large tiles of K
+        // Nvidia prefers shared memory use to load large tiles of K.
+        // Switch to loading from global memory when it would use too much shared memory.
         // AMD prefers loading K directly from global memory
-        const uint32_t k_load_shmem = device->vendor_id == VK_VENDOR_ID_NVIDIA ? 1 : 0;
+        const uint32_t k_load_shmem = device->vendor_id == VK_VENDOR_ID_NVIDIA && hsk < 256 ? 1 : 0;
 
         return {wg_size, rows_cols[0], rows_cols[1], hsk, hsv, clamp, D_split, device->subgroup_size, k_load_shmem};
     };
@@ -8412,7 +8413,7 @@ static bool ggml_vk_flash_attn_coopmat_shmem_support(const vk_device& device, co
     const uint32_t sfshstride = (hsk <= 128) ? (Br + 8) : Br;
     const uint32_t sfsh = Bc * sfshstride * acctype;
 
-    const bool k_load_shmem = device->vendor_id == VK_VENDOR_ID_NVIDIA;
+    const bool k_load_shmem = device->vendor_id == VK_VENDOR_ID_NVIDIA && hsk < 256;
     const uint32_t kshstride = (k_load_shmem ? hsk_pad : MatBr) / 4 + 2;
     const uint32_t vsh_stride = MatBc / 4 * row_split;
     const uint32_t ksh = ((kshstride >= vsh_stride) ? (Bc * kshstride) : (Bc * vsh_stride)) * f16vec4;