TimelinePoint

Remarks

The unit of cross-queue synchronisation, and deliberately not a handle. A caller waits for a submission it made rather than for a semaphore it allocated, which is the difference between "the compute segment's dispatches have finished" and "somebody signalled something". Submitting is how one is obtained — Submit returns the point its own work reaches — so the natural way to use this is also the correct one.

⚠ It is a plain record and one can be built by hand, which nothing should do. A value beyond what will ever be signalled is a device-side hang with no validation message and no stack. The type cannot prevent it — the constructor is what deserialisation, the debugger and a test all need — so the check lives where it is cheap instead: NullDevice refuses a point its queues never issued.

⚠ One counter per queue, never one per device. A single counter shared across queues would have to be signalled with increasing values by submissions that finish in an order nobody controls, and a timeline semaphore signalled backwards is invalid usage. Per queue, submissions finish in the order they were made and the counter only climbs.

⚠ Queue is which submitter, not which hardware queue. On a device whose graphics and compute kinds land on one family they share a counter, so a Compute point and a Graphics point are two values on the same timeline — and waiting for one from the other is satisfied by submission order alone. That is exactly what makes a one-queue device produce the same frame as a two-queue one.

Fields and properties (4)

• public QueueKind Queue

  Whose history it is a point in.

• public ulong Value

  How many submissions that queue has to have finished to have reached it. Counted from 1; 0 is None, the point every queue has already passed.

• public static TimelinePoint None

  The point every queue has already reached, which waiting for costs nothing.

• public bool IsNone

  Whether it is None.

Methods (1)

• public TimelinePoint(QueueKind Queue, ulong Value)

  A point in one queue's submission history, which another submission may wait for.

Used by (9)

• CommandRecorderTestsVixen.Graphics.Null.Tests
• DeviceQueuesVixen.Graphics.RenderGraph
• ICommandSubmitterVixen.Graphics
• NullSubmitterVixen.Graphics.Null
• TimelinePointTestsVixen.Graphics.Tests
• TimelineSubmissionTestsVixen.Graphics.RenderGraph.Tests
• TimelineSubmitTestsVixen.Graphics.Vulkan.Tests
• VulkanDeviceVixen.Graphics.Vulkan
• VulkanQueueVixen.Graphics.Vulkan