From dab226628dde97abb9ce9d0d1281c0dbfaba0a3a Mon Sep 17 00:00:00 2001 From: Mike Lothian Date: Sun, 27 Sep 2026 13:29:47 +0100 Subject: [PATCH 17/18] vulkan : stage large writes to host-visible VRAM through a DMA copy Assisted-by: Claude Code (Claude Opus 5.5) --- ggml/src/ggml-vulkan/ggml-vulkan-buffers.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/ggml/src/ggml-vulkan/ggml-vulkan-buffers.cpp b/ggml/src/ggml-vulkan/ggml-vulkan-buffers.cpp index 4d4c84951..82571f916 100644 --- a/ggml/src/ggml-vulkan/ggml-vulkan-buffers.cpp +++ b/ggml/src/ggml-vulkan/ggml-vulkan-buffers.cpp @@ -496,8 +496,9 @@ bool ggml_vk_buffer_write_async(vk_context subctx, vk_buffer& dst, size_t offset void ggml_vk_buffer_write_2d(vk_buffer& dst, size_t offset, const void * src, size_t spitch, size_t dpitch, size_t width, size_t height) { VK_LOG_DEBUG("ggml_vk_buffer_write_2d(" << width << ", " << height << ")"); - // Buffer is already mapped - if(dst->memory_property_flags & vk::MemoryPropertyFlagBits::eHostVisible) { + // Buffer is already mapped. Large writes to host-visible VRAM (resizable BAR) are faster as a DMA copy than CPU stores over PCIe. + const bool bar = (dst->memory_property_flags & vk::MemoryPropertyFlagBits::eDeviceLocal) && !dst->device->uma; + if ((dst->memory_property_flags & vk::MemoryPropertyFlagBits::eHostVisible) && !(bar && width * height >= (4u << 20))) { GGML_ASSERT(dst->memory_property_flags & vk::MemoryPropertyFlagBits::eHostCoherent); if (width == spitch && width == dpitch) { -- 2.55.0