tmp: env chunk size override

ggml/src/ggml-vulkan/ggml-vulkan.cpp

@@ -17961,6 +17961,12 @@ static bool ggml_backend_vk_register_host_buffer(void * buffer, size_t size) {
         if (chunk == 0) {
             continue;
         }
+        if (getenv("GGML_VK_PIN_CHUNK")) {
+            size_t env_chunk = strtoull(getenv("GGML_VK_PIN_CHUNK"), nullptr, 10);
+            if (env_chunk > 0) {
+                chunk = env_chunk & ~(align - 1);
+            }
+        }
 
         uint8_t * p = static_cast<uint8_t *>(buffer);
         size_t remaining = size;