Tool/software: Linux
Hi all
I was using usleep in DM8168 and found something strange. we know DM8168 run in 100HZ(CONFIG_HZ) by default， it means the minimum sleep time is 10 ms(microsecond).we can't sleep for less that 10ms, because that's the resolution of the scheduler.right?
But after testing,i get this:
root@dm816x:~/xxx# ./test_sleep
function time(usec) realTime reduce
-------------------------------------------------------------------
----------------------------
usleep 500000 500082 82
select 500000 500513 513
----------------------------
usleep 100000 100086 86
select 100000 100142 142
----------------------------
usleep 50000 50072 72
select 50000 50072 72
----------------------------
usleep 10000 10071 71
select 10000 10072 72
----------------------------
usleep 1000 1073 73
select 1000 1071 71
----------------------------
usleep 900 970 70
select 900 972 72
----------------------------
usleep 500 571 71
select 500 572 72
----------------------------
usleep 100 181 81
select 100 172 72
----------------------------
usleep 10 80 70
select 10 81 71
----------------------------
usleep 1 71 70
select 1 72 71
----------------------------
usleep 0 70 70
select 0 4 4
----------------------------
usleep 0 71 71
select 0 4 4
it seems the minimum sleep time is only 70us with usleep,and 4us with select.how usleep can broke up the scheduler?
Can anyone tell me ?
Best Regards
