lkml.org 
[lkml]   [2006]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/14] RTC: Remove RTC UIP synchronization on x86
    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/

    \
     
     \ /
      Last update: 2006-03-21 16:15    [from the cache]
    ©2003-2011 Jasper Spaans. Advertise on this site