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: <20090624102915.4df3fa85@lxorguk.ukuu.org.uk>
Date:	Wed, 24 Jun 2009 10:29:15 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	john stultz <johnstul@...ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Miroslav Lichvar <mlichvar@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [GIT pull] ntp updates for 2.6.31

> On Tue, 2009-06-23 at 15:36 +0200, Ingo Molnar wrote:
> > The PPS patches i've seen just export IRQ timestamps to user-space.

Correct. They improve the sampling information quality and help cut down
on jitter between the IRQ sampling and using the timestamp. The jitter is
what matters most here and NTP can figure out constant latencies rather
well.

> At some point that stops being NTP. NTP has quite a bit of userland
> policy for filtering and managing a number of different network clocks
> (other ntp servers, PPS sources, etc).
> 
> >From what you're describing (direct offset from a hardware time device
> used to steer the clock directly in kernel), you might want to look at
> the STP code in s390 (stp_sync_clock).

And also hardware distributed timing systems like those that distribute a
clock with ethernet signals.

Alan
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ