Messages in this thread | | | Date | Sun, 19 Mar 2006 18:13:36 +0000 | From | Pavel Machek <> | Subject | Re: [PATCH 1/14] RTC: Remove RTC UIP synchronization on x86 |
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Hi!
> Remove RTC UIP synchronization on x86 > > Reading the CMOS clock on x86 and some other arches currently takes up > to one second because it synchronizes with the CMOS second tick-over. > This delay shows up at boot time as well a resume time. > > This is the currently the most substantial boot time delay for > machines that are working towards instant-on capability. Also, a quick > back of the envelope calculation (.5sec * 2M users * 1 boot a day * 10 years) > suggests it has cost Linux users in the neighborhood of a million > man-hours.
Heh, nice manipulation attempt. Note you are also introduced timing error of about 114 years total.
> In my view, there are basically four cases to consider: > > 1) networked, need precise walltime: use NTP > 2) networked, don't need precise walltime: use NTP anyway > 3) not networked, don't need sub-second precision walltime: don't care > 4) not networked, need sub-second precision walltime: > get a network or a radio time source because RTC isn't good enough anyway
Eh, very nice, so I should get radio time source for my notebook?
> So this patch series simply removes the synchronization in favor of a > simple seqlock-like approach using the seconds value.
What about polling RTC from timer interrupt or something like that, so that you get error in range of 5 msec instead of 500 msec? You can do the calibration in parallel, then... Pavel -- Thanks, Sharp! - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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