Re: Can't sleep less than 20 ms
Marcus Meissner (marcus@jet.franken.de)
Fri, 2 Jul 1999 17:18:26 +0200
In article <19990702073845.A27173@revue.linux-kernel-luna.science-computing.de> you write:
>On Thu, Jul 01, 1999 at 06:12:24PM -0400, Dong Liu wrote:
>> Hi,
>>
>> I know Linux on i386 has a timer resolution of 10 ms, but
>> why I can't sleep for 10 ms, I can only sleep at
>> interval of 20 , 30, 40 ... ms.
>
>this is what the man page says :
>
>(from man 3 usleep)
>...
>DESCRIPTION
> The usleep() function suspends execution of the calling
> process for usec microseconds. The sleep may be length
> ened slightly by any system activity or by the time spent
> processing the call.
>...
Won't help, usleep(3) uses nanosleep(2) which uses the 1/HZ (10ms) timers
under the normal scheduling type. Check the manpage on nanosleep(2).
If you set the scheduler to SCHED_RR or SCHED_FIFO nanosleep(2) does up
to 2ms busy waits (finegrained sleep) and then switches back to the standard
10ms timer.
Ciao, Marcus
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