lkml.org 
[lkml]   [2005]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: HZ question


On Tue, 13 Sep 2005, Mark Hounschell wrote:

> On a 100HZ kernel ANY requested delay via udelay or
> pthread_cond_timedwait of less than 10000usecs is unreliable and the the
> actual results are totally unacceptable.
>
> On a 1000HZ kernel the number is 1000 usecs.
>
> I'm not asking the kernel running at 1000hz to actually give me 500 usec
> delay if I ask. I do expect it to be at least 500 usec and within +- a
> single HZ however.

The kernel just cannot guarantee the latter. Rounding is only one of
many issues here.
Do you also want to know about CONFIG_PREEMPT, SMP, current load, future
load in order to estimate the delay you want to ask for?

OTOH, I'm not a soft real-time expert, so I'll stop commenting here.

Tim
-
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/

\
 
 \ /
  Last update: 2005-09-13 18:04    [from the cache]
©2003-2011 Jasper Spaans