8 May
2005
8 May
'05
2:15 p.m.
Hi Lee,
Interesting.
But what's the exact behaviour in 2.6 kernels then ?
Does nanosleep() provide non-busywait usec precision using hires timers,
or does it simply do the same as usleep() ?
Eg providing only 1/HZ precison.
cheers,
Benno
http://www.linuxsampler.org
Lee Revell wrote:
Right,
nanosleep() might be a bit more precise than usleep() but for low sleep
values ( AFAIK < 2msec ) it
busywaits when you run your app SCHED_FIFO which in the case of
sustained streams of low sleep values
could chew up all the CPU, not idea for real time audio apps.
Not anymore. From man 2 nanosleep:
Old behaviour
In order to support applications requiring much more precise
pauses (e.g., in order to control some time-critical hardware),
nanosleep would handle pauses of up
to 2 ms by busy waiting with microsecond precision when called
from a process scheduled under a real-time policy like SCHED_FIFO or
SCHED_RR. This special
extension was removed in kernel 2.5.39, hence is still present in
current 2.4 kernels, but not in 2.6 kernels.
Lee