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SubjectRe: LinuxPPS low-level IRQs timestamps & ldisc
On Mon, Jun 02, 2008 at 04:48:40PM +0100, Alan Cox wrote:
> > I prefere avoid the if clause for getnstimeofday() since each
> > instruction delay may decrease time precision, so:
>
> Why should everyone else pay the cost of the getnstimeofday they don't
> need ?
>
> The single conditional check at the start won't make the slightest
> material difference to your accuracy.

In the past we noticed that just moving up the getnstimeofday() of
only one instruction, from:

port->icount.dcd++;
getnstimeofday(&ts);

to:

getnstimeofday(&ts);
port->icount.dcd++;

the time precision improved from 5ms to 2ms...

However, if you prefere that I add the if clause, I'll do it.

Thanks,

Rodolfo

--

GNU/Linux Solutions e-mail: giometti@enneenne.com
Linux Device Driver giometti@linux.it
Embedded Systems phone: +39 349 2432127
UNIX programming skype: rodolfo.giometti


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