使用时间线信号量时的 vkQueueSubmit 块

Question

我需要在两个 GPU 批次之间运行 CPU 上的一个函数。为此，我使用时间线信号量。据我所知，vkQueueSubmit 不会阻塞。但是，当我提交这些 GPU 批次时它会阻塞：

uint64_t host_wait = timeline;
uint64_t host_signal = ++timeline;

uint64_t wait0 = timeline;
uint64_t signal0 = ++timeline;
uint64_t wait1 = timeline;
uint64_t signal1 = ++timeline;

VkPipelineStageFlags wait_mask = VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT;

VkTimelineSemaphoreSubmitInfo sp_submit0 = {
    .sType                     = VK_STRUCTURE_TYPE_TIMELINE_SEMAPHORE_SUBMIT_INFO,
    .waitSemaphoreValueCount   = 1,
    .pWaitSemaphoreValues      = &wait0,
    .signalSemaphoreValueCount = 1,
    .pSignalSemaphoreValues    = &signal0,
};
VkSubmitInfo submit0 = {
    .sType                = VK_STRUCTURE_TYPE_SUBMIT_INFO,
    .pNext                = &sp_submit0,
    .waitSemaphoreCount   = 1,
    .pWaitSemaphores      = &timeline_semaphore,
    .pWaitDstStageMask    = &wait_mask,
    .signalSemaphoreCount = 1,
    .pSignalSemaphores    = &timeline_semaphore,
};

VkTimelineSemaphoreSubmitInfo sp_submit1 = {
    .sType                     = VK_STRUCTURE_TYPE_TIMELINE_SEMAPHORE_SUBMIT_INFO,
    .waitSemaphoreValueCount   = 1,
    .pWaitSemaphoreValues      = &wait1,
    .signalSemaphoreValueCount = 1,
    .pSignalSemaphoreValues    = &signal1,
};
VkSubmitInfo submit1 = {
    .sType                = VK_STRUCTURE_TYPE_SUBMIT_INFO,
    .pNext                = &sp_submit1,
    .waitSemaphoreCount   = 1,
    .pWaitSemaphores      = &timeline_semaphore,
    .pWaitDstStageMask    = &wait_mask,
    .commandBufferCount   = 1,
    .pCommandBuffers      = &command_buffer,
    .signalSemaphoreCount = 1,
    .pSignalSemaphores    = &timeline_semaphore,
};

VkSubmitInfo infos[2] = { submit0, submit1 };
vkQueueSubmit(queue, 2, infos, fence);
// here vkQueueSubmit blocks the thread

WaitSemaphore(timeline_semaphore, host_wait);
some_function();
SignalSemaphore(timeline_semaphore, host_signal);

没有return它会阻塞几秒钟，我认为这有点像死锁。在调试器中，我看到来自 vkQueueSubmit 的 SleepEx 函数调用：vk_icdGetInstanceProcAddrSG -> ... -> SleepEx.

但是vkQueueSubmit在这个样本中没有阻塞（合并批处理）：

uint64_t host_wait = timeline;
uint64_t host_signal = ++timeline;

uint64_t wait1 = timeline;
uint64_t signal1 = ++timeline;

VkPipelineStageFlags wait_mask = VK_PIPELINE_STAGE_TOP_OF_PIPE_BIT;

VkTimelineSemaphoreSubmitInfo sp_submit1 = {
    .sType                     = VK_STRUCTURE_TYPE_TIMELINE_SEMAPHORE_SUBMIT_INFO,
    .waitSemaphoreValueCount   = 1,
    .pWaitSemaphoreValues      = &wait1,
    .signalSemaphoreValueCount = 1,
    .pSignalSemaphoreValues    = &signal1,
};
VkSubmitInfo submit1 = {
    .sType                = VK_STRUCTURE_TYPE_SUBMIT_INFO,
    .pNext                = &sp_submit1,
    .waitSemaphoreCount   = 1,
    .pWaitSemaphores      = &timeline_semaphore,
    .pWaitDstStageMask    = &wait_mask,
    .commandBufferCount   = 1,
    .pCommandBuffers      = &command_buffer,
    .signalSemaphoreCount = 1,
    .pSignalSemaphores    = &timeline_semaphore,
};

VkSubmitInfo infos[1] = { submit1 };
vkQueueSubmit(queue, 1, infos, fence);

WaitSemaphore(timeline_semaphore, host_wait);
some_function();
SignalSemaphore(timeline_semaphore, host_signal);

为什么 vkQueueSubmit 在第一个代码示例中阻塞？这个问题的可能原因是什么？我在 Windows 10 和 Radeon RX 570（驱动程序 20.4.2）上使用 Vulkan 1.2 (SDK 1.2.135)。

编辑：当我将命令缓冲区添加到 submit0 时，vkQueueSubmit 不会阻塞。这是驱动程序中的错误吗？

Answer 1

Doing something odd like submitting a batch with no work is far more likely to be the cause.

The spec doesn’t have performance requirements. The fact that something is legal does not make it a good idea. Broadly speaking, if there are two ways to do a thing, do it the obvious way. And sending an empty batch isn’t exactly obvious

https://community.khronos.org/t/vkqueuesubmit-blocks-when-using-timeline-semaphores/105704/2

使用时间线信号量时的 vkQueueSubmit 块

vkQueueSubmit blocks when using timeline semaphores

c++

vulkan