From mboxrd@z Thu Jan 1 00:00:00 1970 From: john stultz Date: Thu, 29 Jul 2004 18:37:51 +0000 Subject: Re: [PATCH] minor cyclone cleanup Message-Id: <1091126270.1388.622.camel@cog.beaverton.ibm.com> List-Id: References: <200407291054.05720.bjorn.helgaas@hp.com> In-Reply-To: <200407291054.05720.bjorn.helgaas@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Thu, 2004-07-29 at 10:13, Bjorn Helgaas wrote: > On Thursday 29 July 2004 11:02 am, john stultz wrote: > > Stay tuned! As soon as I finish reworking the NTP code bI'll be mailing > > out code. > > Ah, an NTP expert :-) Ha! Hardly. Although after looking at the kernel code, I'm starting to wonder if anyone was ever. And even if I learn a thing or two about the topic, I'm sure to disavow all knowledge for fear of being pigeon-holed for the rest of my life ;) > What do you think about adding an RTC driver > to NTP? On our boxes (and I suspect many others), the system clock > is driven by the interval timer. But the RTC is much more accurate, > so it'd be nice if NTP knew how to use it. With my re-work, the system clock is driven from a time-source, not the interval timer. That time-source is the only semi-arch-specific bit in the code, so it can be the ITC, the cyclone counter, HPET, or even the RTC. Its not all that different then ia64's time_interpolator infrastructure, just cleaned up and simplified a bit. > The RTC is terribly slow and has low resolution, but in the absence of > anything better, it'd be nice if we could use it. Indeed, using the RTC for gettimeofday and friends would be quite painful, and almost so low res as to be worthless, so I doubt you'd really want to use it. > Is this possible? Feasible? I know the NTP guys would probably > laugh us out of the room, but not everybody has a fancy clock > attached to their box. Another idea would be to make a userspace daemon who would read the RTC and use the kernel's adjtimex() syscall to manipulate time. This would be just like the userspace NTP daemon, only using the RTC instead of a timeserver. Not having sub-second resolution would mean it would have to be conservative and take quite some time to sync up, but it would be possible. Whats wrong with using regular NTP, btw? thanks -john