Messages in this thread | | | Date | Tue, 14 Jun 2005 10:57:44 +0200 | From | quade <> | Subject | Re: latency error (~2ms) with nanosleep |
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On Mon, Jun 13, 2005 at 09:54:47AM -0700, Nish Aravamudan wrote: > 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/ - 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/
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