Re: LinuxPPS low-level IRQs timestamps & ldisc

[Rodolfo Giometti]

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@xxxxxxxxxxxx
Linux Device Driver                             giometti@xxxxxxxx
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UNIX programming                     skype:     rodolfo.giometti
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