On 02.07.2008, at 14:29, Werner Coetzee wrote:
Hi
Can anyone explain why gwthread is using the poll function to sleep
(using milliseconds as timeout), and not maybe the select function
(using microseconds as timeout)?
Kannel can use poll or select. It's a platform specific decision by ./
configure as not all have poll as far as I remember.
Select has an issue if you have a lot of file descriptors open as it
uses an array of many fd's. poll is much smarter there.
The reason why kannel uses poll on a pipe to sleep is for the simple
reason that a thread can be woken up before the sleep time expires by
sending a byte to the pipe.
We have the requirement to be able to sleep for less than a
millisecond, which the current gwthread_sleep can't provide.
If its for pure sleeping of such small time amounts, you might consult
your operating system's documentation. maybe usleep() or nanosleep()
is better for such cases. However be aware that if you sleep such
small amounts, accuracy can become an issue. Unix kernels are not real
time kernels.
usleep() on MacOS X says:
DESCRIPTION
The usleep() function suspends execution of the calling thread
until either useconds microseconds have elapsed or a signal is deliv-
ered to the thread whose action is to invoke a signal-catching
function or to terminate the thread or process. The actual time
slept may be longer, due to system latencies and possible
limitations in the timer resolution of the hardware.
This function is implemented, using nanosleep(2), by pausing for
useconds microseconds or until a signal occurs. Consequently, in
this implementation, sleeping has no effect on the state of
process timers and there is no special handling for SIGALRM.
Andreas Fink
Fink Consulting GmbH
Global Networks Schweiz AG
BebbiCell AG
IceCell ehf
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