Tobias Hector tobski
In Vulkan, users can specify device-scope queue priorities.
In some cases it may be useful to extend this concept to a system-wide
This device extension allows applications to query the global queue
priorities supported by a queue family, and then set a priority when
The default queue priority is
Implementations can report which global priority levels are treated differently by the implementation. It is intended primarily for use in system integration along with certain platform-specific priority enforcement rules.
The driver implementation will attempt to skew hardware resource allocation in favour of the higher-priority task. Therefore, higher-priority work may retain similar latency and throughput characteristics even if the system is congested with lower priority work.
The global priority level of a queue shall take precedence over the
per-process queue priority
Abuse of this feature may result in starving the rest of the system from
Therefore, the driver implementation may deny requests to acquire a priority
above the default priority (
the caller does not have sufficient privileges.
In this scenario
VK_ERROR_NOT_PERMITTED_EXT is returned.
The driver implementation may fail the queue allocation request if resources
required to complete the operation have been exhausted (either by the same
process or a different process).
In this scenario
VK_ERROR_INITIALIZATION_FAILED is returned.
1) Can we additionally query whether a caller is permitted to acquire a specific global queue priority in this extension?
RESOLVED: No. Whether a caller has enough privilege goes with the OS, and the Vulkan driver cannot really guarantee that the privilege will not change in between this query and the actual queue creation call.
2) If more than 1 queue using global priority is requested, is there a good way to know which queue is failing the device creation?
RESOLVED: No. There is not a good way at this moment, and it is also not quite actionable for the applications to know that because the information may not be accurate. Queue creation can fail because of runtime constraints like insufficient privilege or lack of resource, and the failure is not necessarily tied to that particular queue configuration requested.
For more information, see the Vulkan Specification
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