linux-kernel - Re: LinuxPPS low-level IRQs timestamps & ldisc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080602202135.GF3700@mea-ext.zmailer.org>
Date:	Mon, 2 Jun 2008 23:21:35 +0300
From:	Matti Aarnio <matti.aarnio@...iler.org>
To:	Rodolfo Giometti <giometti@...eenne.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: LinuxPPS low-level IRQs timestamps & ldisc

On Mon, Jun 02, 2008 at 07:22:03PM +0200, Rodolfo Giometti wrote:
...
> 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...

Perhaps I am looking for unattainable..  but I have HP/Agilent 58534A
(a.k.a Symmetricom 58534A) "GPS Timing Antenna",  which specifications
are telling that it should attain 1PPS timing jitter of less than 40 ns
in proper stabilized position hold mode.

Can that level be handled with standard PC hardware, or should the time
keeping and core parts of NTP be delegated into FPGA entirely ?
Stratum-1 is rather demanding, after all...

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

Thanks,  Matti
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/