- Mon Jan 14, 2019 10:44 pm
#80065
Quick question: At what priority does a tmr timer alarm callback run? I've tried to trace it in source but keep getting lost in the weeds. I'm guessing from information in the FAQ that it's posting a task to the medium priority queue, but since the task queues have very different timing constraints, I want to be sure.
- Sat Jan 19, 2019 4:27 pm
#80151
No answers yet, so I devised an experiment. Drop some tasks on each queue and also start some timers, see how they group:
What I expected to see was the tmr 1 2 3 messages grouped with one set of task queue messages, probably the priority 1, 'med' ones. What I got was this:
It appears that tmr callbacks run at a higher priority even than high-priority task callbacks. This would suggest that tmr callbacks should be really, really brief. Per the Developer FAQ, "The general recommendation is to keep medium priority tasks under 2mSec and low priority tasks under 15 mSec in duration. " There's no specific recommendation for high priority tasks, but I would assume it would be something under 2mSec. What would be the recommendation for tmr callbacks, I wonder?
Code: Select all
function task_print(x)
print(x)
end
node.task.post(0, function() task_print('low 1') end)
node.task.post(0, function() task_print('low 2') end)
t1 = tmr.create()
t1:alarm(1, tmr.ALARM_SINGLE, function() task_print('tmr 1') end)
node.task.post(0, function() task_print('low 3') end)
node.task.post(1, function() task_print('med 1') end)
node.task.post(1, function() task_print('med 2') end)
t2 = tmr.create()
t2:alarm(1, tmr.ALARM_SINGLE, function() task_print('tmr 2') end)
node.task.post(1, function() task_print('med 3') end)
node.task.post(2, function() task_print('hig 1') end)
node.task.post(2, function() task_print('hig 2') end)
t3 = tmr.create()
t3:alarm(1, tmr.ALARM_SINGLE, function() task_print('tmr 3') end)
node.task.post(2, function() task_print('hig 3') end)
print('Setup done')What I expected to see was the tmr 1 2 3 messages grouped with one set of task queue messages, probably the priority 1, 'med' ones. What I got was this:
Code: Select all
dofile("logtmr.lua")
Setup done
> tmr 1
tmr 2
tmr 3
hig 1
hig 2
hig 3
med 1
med 2
med 3
low 1
low 2
low 3
It appears that tmr callbacks run at a higher priority even than high-priority task callbacks. This would suggest that tmr callbacks should be really, really brief. Per the Developer FAQ, "The general recommendation is to keep medium priority tasks under 2mSec and low priority tasks under 15 mSec in duration. " There's no specific recommendation for high priority tasks, but I would assume it would be something under 2mSec. What would be the recommendation for tmr callbacks, I wonder?
