Use unspecified QoS in QueueScheduler when QoS is unspecified #880
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Issue
after doing a bit of research on how libdispatch's 'quality of service' (QoS) propagation logic works, i noticed that the default behavior of
QueueScheduler
is slightly different than what one would get if just using aDispatchQueue
. i'm not sure if this was intentional, but in practice the consequence is that if you do something like this:you end up with the inferred QoS of the scheduled block being set to 'default' QoS, whereas it would be 'user initiated' if using a vanilla
DispatchQueue
. this patch changes the defaultqos
parameter from.default
to.unspecified
to matchDispatchQueue
's default behavior. this change might alter behavior of existing code; hopefully not in a detrimental way, but rather will apply the appropriate QoS propagation that one would assume would occur by default. unfortunately, i realize it's probably impossible to determine if this will cause undesirable changes in existing client code, so i'm open to a different approach or not making this change (though IMO it is semantically more appropriate).Description
QueueScheduler
'sqos
parameter from.default
to.unspecified
Checklist