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    SubjectRe: [PATCH] x86: Export tsc related information in sysfs
    On 05/26/2010 03:49 PM, john stultz wrote:
    > On Wed, 2010-05-26 at 14:44 -0400, Brian Bloniarz wrote:
    >> On 05/26/2010 12:25 PM, john stultz wrote:
    >>> Brian: is this something the NTPd folks actually want? Has anyone
    >>> checked with them before we hand down the solution from high upon on
    >>> lkml mountain?
    >> I haven't checked, it's been a while since I dealt with
    >> this problem. The NTP maintainers definitely complain about the
    >> quick TSC calibration code like it's a bug:
    >> (e.g.
    >> Anyway I'll reach out before I spend any time investing in
    >> a solution that they don't want (and you don't like :).
    >>> Personally I think NTPd should be a little more savvy about how far it
    >>> trusts the drift file when it starts up. Since I believe its
    >>> fast-startup mode can quickly estimate the drift well within 100ppm,
    >>> which is about the maximum variance I've seen from the calibration code.
    >> The workaround we went with was to remove the drift file on
    >> every reboot. But in our experience, even with iburst, converging takes
    >> a long time. I don't have hard numbers since it's been a long time since
    >> I investigated the problem, but we defined failure as >1ms offset syncing
    >> to a server in our LAN, and a cold NTP boot takes 10-20 hours to get
    >> there.
    > Ok. If its been awhile, you may find recent kernels (2.6.31+) are much
    > faster to converge due to adjustments made to the SHIFT_PLL constant.
    > This was done explicitly to address issues similar to what you describe
    > above.

    My tests were pre-2.6.31, this is really good to know. I'll take
    another look on recent kernels.

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      Last update: 2010-05-26 22:25    [W:0.023 / U:1.144 seconds]
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