Messages in this thread | | | Date | Mon, 13 Jun 2005 09:54:47 -0700 | From | Nish Aravamudan <> | Subject | Re: latency error (~2ms) with nanosleep |
| |
On 6/13/05, Chris Friesen <cfriesen@nortel.com> wrote: > quade wrote: > > Playing around with the (simple) measurement of latency-times > > I noticed, that the systemcall "nanosleep" has always a minimal > > latency from about ~2ms (haven't run it all night, so...). It > > seems to be a systematical error. > > Known issue. The x86 interrupt usually has a period of slightly less > than a ms. It will therefore generally add nearly a whole ms to ensure > that it does not ever wait for *less* than specified.
Exactly. And the sys_nanosleep() code adds one more if the parameter has any positive value at all:
expire = timespec_to_jiffies(&t) + (t.tv_sec || t.tv_nsec); current->state = TASK_INTERRUPTIBLE; expire = schedule_timeout(expire);
Thanks, Nish - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |