lkml.org 
[lkml]   [2009]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Linux 2.6.29-rc6
    Linus Torvalds wrote:
    >
    > Jesper, here's a patch that actually tries to take teh TSC error really
    > into account, and which I suspect will result (on your machine) in failing
    > the fast PIT calibration.
    >
    > It also has a few extra printk's for debugging, and to see just what the
    > values are on your machine.
    >
    > The idea behind the patch is to just keep track of how big the difference
    > was in TSC values between two successive reads of the PIT timer. We only
    > really care about the difference when the MSB turns around, and we only
    > really care about the two end points. The maximum error in TSC estimation
    > will simply be the sum of the differences at those points (d1 and d2).
    >
    > We can then compare the maximum error with the actual TSC differences
    > between those points, and see if the max error is within 500 ppm. That
    > _should_ mean that it all works - assuming that the PIT itself is running
    > at the correct frequency, of course!
    >
    > Regardless of whether is succeeds or not, it will print out some debug
    > messages, which will be interesting to see.


    [ 0.000000] Fast TSC delta=34227730, error=6223+6219=12442
    [ 0.000000] Fast TSC calibration using PIT
    [ 0.000000] Detected 2312.045 MHz processor.

    Using "ntpq -c peers" .. the offset steadily grows as time goes.

    Full dmesg: http://krogh.cc/~jesper/dmesg-linux-2.6.29-rc8-linus1.txt

    jk@quad11:~$ ntpdc -c kerninfo
    pll offset: 0.085167 s
    pll frequency: -18.722 ppm
    maximum error: 0.137231 s
    estimated error: 0.008823 s
    status: 0001 pll
    pll time constant: 6
    precision: 1e-06 s
    frequency tolerance: 500 ppm



    --
    Jesper




    \
     
     \ /
      Last update: 2009-03-15 16:47    [W:0.026 / U:0.980 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site