Vulkan 是一个低开销、跨平台的二维和三维图形与计算的应用程序接口，由 Khronos 在2015年在 GDC 上首次发布。它旨在提供高效能和更均衡的 CPU 和 GPU 占用，类似于 Direct3D 12 和 AMD Mantle。

本文主要记录一下在 llvmpipe 软渲染 Vulkan 驱动下， 一个 vulkan 应用程序 (demo) 的执行过程。

VK_ICD_FILENAMES

Vulkan 驱动的探测和加载是通过 ICD (Installable Client Driver) 机制实现的。当环境上同时存在多个 Vulkan 驱动时，使用环境变量 VK_ICD_FILENAMES 来选择指定的 vulkan 驱动

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{
    "name": "VK_ICD_FILENAMES",
    "value": "/home/luc/mesa-install/share/vulkan/icd.d/lvp_icd.x86_64.json"
}

MESA_VK_WSI_PRESENT_MODE

Vulkan 程序的送显由 WSI (Window System Interface) 层实现，支持以下模式

  • fifo
  • relaxed
  • mailbox
  • immediate

Call Stack

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libvulkan_lvp.so!llvmpipe_create_screen(struct sw_winsys * winsys) (\home\luc\gh\forked\src\gallium\drivers\llvmpipe\lp_screen.c:1149)
libvulkan_lvp.so!sw_screen_create_named(struct sw_winsys * winsys, const struct pipe_screen_config * config, const char * driver) (\home\luc\gh\forked\src\gallium\auxiliary\target-helpers\sw_helper.h:43)
libvulkan_lvp.so!sw_screen_create_vk(struct sw_winsys * winsys, const struct pipe_screen_config * config, _Bool sw_vk) (\home\luc\gh\forked\src\gallium\auxiliary\target-helpers\sw_helper.h:90)
libvulkan_lvp.so!pipe_loader_sw_create_screen(struct pipe_loader_device * dev, const struct pipe_screen_config * config, _Bool sw_vk) (\home\luc\gh\forked\src\gallium\auxiliary\pipe-loader\pipe_loader_sw.c:427)
libvulkan_lvp.so!pipe_loader_create_screen_vk(struct pipe_loader_device * dev, _Bool sw_vk, _Bool driver_name_is_inferred) (\home\luc\gh\forked\src\gallium\auxiliary\pipe-loader\pipe_loader.c:181)
libvulkan_lvp.so!lvp_physical_device_init(struct lvp_physical_device * device, struct lvp_instance * instance, struct pipe_loader_device * pld) (\home\luc\gh\forked\src\gallium\frontends\lavapipe\lvp_device.c:1240)
libvulkan_lvp.so!lvp_enumerate_physical_devices(struct vk_instance * vk_instance) (\home\luc\gh\forked\src\gallium\frontends\lavapipe\lvp_device.c:1416)
libvulkan_lvp.so!enumerate_physical_devices_locked(struct vk_instance * instance) (\home\luc\gh\forked\src\vulkan\runtime\vk_instance.c:434)
libvulkan_lvp.so!enumerate_physical_devices(struct vk_instance * instance) (\home\luc\gh\forked\src\vulkan\runtime\vk_instance.c:459)
libvulkan_lvp.so!vk_common_EnumeratePhysicalDevices(VkInstance _instance, uint32_t * pPhysicalDeviceCount, VkPhysicalDevice * pPhysicalDevices) (\home\luc\gh\forked\src\vulkan\runtime\vk_instance.c:475)
libvulkan.so.1![Unknown/Just-In-Time compiled code] (Unknown Source:0)
libvulkan.so.1!vkEnumeratePhysicalDevices (Unknown Source:0)
vk::DispatchLoaderStatic::vkEnumeratePhysicalDevices(const vk::DispatchLoaderStatic * const this, VkInstance instance, uint32_t * pPhysicalDeviceCount, VkPhysicalDevice * pPhysicalDevices) (\usr\local\include\vulkan\vulkan.hpp:1047)
vk::Instance::enumeratePhysicalDevices<std::allocator<vk::PhysicalDevice>, vk::DispatchLoaderStatic>(const vk::DispatchLoaderStatic & d, const vk::Instance * const this) (\usr\local\include\vulkan\vulkan_funcs.hpp:120)
vks::Context::pickDevice(vks::Context * const this, const vk::SurfaceKHR & surface) (\home\luc\gh\VulkanExamples\base\vks\context.hpp:426)
vks::Context::createDevice(vks::Context * const this, const vk::SurfaceKHR & surface) (\home\luc\gh\VulkanExamples\base\vks\context.hpp:233)
vkx::ExampleBase::initVulkan(vkx::ExampleBase * const this) (\home\luc\gh\VulkanExamples\base\vulkanExampleBase.cpp:123)
vkx::ExampleBase::run(vkx::ExampleBase * const this) (\home\luc\gh\VulkanExamples\base\vulkanExampleBase.cpp:75)
main(const int argc, const char ** argv) (\home\luc\gh\VulkanExamples\examples\deferredmultisampling\deferredmultisampling.cpp:684)

Debug Options

就像其它 Gallium 驱动一样，llvmpipe 也提供了很多调试和性能测试的选项, 这此选项通过环境变量 LP_DEBUG 和 LP_PERF 来设置

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debug_parse_flags_option: help for LP_DEBUG:
|        pipe [0x0000000000000001]
|        tgsi [0x0000000000000002]
|         tex [0x0000000000000004]
|       setup [0x0000000000000010]
|        rast [0x0000000000000020]
|       query [0x0000000000000040]
|      screen [0x0000000000000080]
|    counters [0x0000000000000800]
|       scene [0x0000000000001000]
|       fence [0x0000000000002000]
| no_fastpath [0x0000000000080000]
|      linear [0x0000000000100000]
|     linear2 [0x0000000000200000]
|         mem [0x0000000000004000]
|          fs [0x0000000000008000]
|          cs [0x0000000000010000]
| accurate_a0 [0x0000000000800000]
|        mesh [0x0000000001000000]
debug_parse_flags_option: help for LP_PERF:
|         texmem [0x0000000000000001]
|      no_mipmap [0x0000000000000004]
|      no_linear [0x0000000000000008]
|  no_mip_linear [0x0000000000000002]
|         no_tex [0x0000000000000010]
|       no_blend [0x0000000000000020]
|       no_depth [0x0000000000000040]
|   no_alphatest [0x0000000000000080]
| no_rast_linear [0x0000000000000100]
|       no_shade [0x0000000000000200]

Gears

Vulkan 应用的“神奇”之处在于，场景在变，而它的 draw() 函数却不随着被反复调用

VulkanExamples-gears