4 ms·

Agreed, if there's no latency cost and no cost to maintaining the queue. But if your queue is never emptying, you've hit an equilibrium where you're persistent

Agreed, if there's no latency cost and no cost to maintaining the queue. But if your queue is never emptying, you've hit an equilibrium where you're persistently overloaded and constantly load shedding. In that case you can reduce the queue size so that it is only just not emptying - you'll still be running at 100% capacity and shedding the same amount of demand. And if there was a latency cost or a cost per item in the queue, you reduce those. Edit: if you have an external control loop that is matching supply and demand, you could be persistently queuing without load shedding, in which case you might want to maintain the standing queue. In the absense of an external control loop, supply and demand will pretty much never be in precise equilibrium, in which case a persistent queue will pretty much always also mean you're load-shedding.

sethammons 3y ago
> But if your queue is never emptying, you've hit an equilibrium where you're persistently overloaded and constantly load shedding I believe this is an incorrect assertion. You have hit equilibrium, yes. But you are not load shedding unless you are preventing new queue entrants. And if you are allowing new entrants and the latency is acceptable to customers, you are not overloaded. Like you said, you are at an equilibrium.
datadrivenangel 3y ago
It sounds like the above poster is in a situation with multiple priority queues, where as long as latency and throughput for high priority items is good, having higher latency for lower priority items is fine, and could be a form of low-cost back pressure on new orders or signalling to improve the throughput a little bit.
sokoloff 3y ago
As long as we are consistently emptying the queue of all orders due to be produced on the next shift, I think we are correctly sized while losing nothing (no load-shedding or turning orders away), even though we carry an overall non-zero backlog essentially permanently. Having 48 hours of weekend where order volume is way down, but processing volume is constant is a key part of maintaining this equilibrium.

sethammons 3y ago

> But if your queue is never emptying, you've hit an equilibrium where you're persistently overloaded and constantly load shedding I believe this is an incorrect assertion. You have hit equilibrium, yes. But you are not load shedding unless you are preventing new queue entrants. And if you are allowing new entrants and the latency is acceptable to customers, you are not overloaded. Like you said, you are at an equilibrium.

datadrivenangel 3y ago

It sounds like the above poster is in a situation with multiple priority queues, where as long as latency and throughput for high priority items is good, having higher latency for lower priority items is fine, and could be a form of low-cost back pressure on new orders or signalling to improve the throughput a little bit.

sokoloff 3y ago

As long as we are consistently emptying the queue of all orders due to be produced on the next shift, I think we are correctly sized while losing nothing (no load-shedding or turning orders away), even though we carry an overall non-zero backlog essentially permanently. Having 48 hours of weekend where order volume is way down, but processing volume is constant is a key part of maintaining this equilibrium.