lkml.org 
[lkml]   [2009]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH RFC: kvm tsc virtualization 13/20] Combine observed TSC deviation into moving average
    Date
    Signed-off-by: Zachary Amsden <zamsden@redhat.com>
    ---
    arch/x86/kvm/x86.c | 14 +++++++++++---
    1 files changed, 11 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index c66dede..8bd362b 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -914,6 +914,7 @@ static void sync_tsc_helper(int measure_cpu, s64 *delta, atomic_t *ready)
    /*
    * Average and trim the samples of any outliers; we use > 2 x sigma
    */
    +static u64 tsc_deviation;
    static s64 average_samples(s64 *samples, unsigned num_samples)
    {
    unsigned i, j;
    @@ -936,6 +937,11 @@ static s64 average_samples(s64 *samples, unsigned num_samples)
    stddev = stddev / (num_samples - 1);
    stddev = int_sqrt(stddev);

    + /* Accumulate deviation measurement into a moving average */
    + tsc_deviation = tsc_deviation ?
    + ((tsc_deviation << 4) - tsc_deviation + stddev) >> 4 :
    + stddev;
    +
    /* Throw out anything outside 2x stddev */
    stddev <<= 1;
    average = 0, j = 0;
    @@ -950,10 +956,12 @@ static s64 average_samples(s64 *samples, unsigned num_samples)
    }
    if (j > 0)
    average = average / j;
    - else
    + else {
    printk(KERN_ERR "kvm: TSC samples failed to converge!\n");
    - pr_debug("%s: mean = %lld, stddev = %llu, average = %lld\n",
    - __func__, mean, stddev, average);
    + average = mean;
    + }
    + pr_debug("%s: mean=%lld, stddev=%llu, average=%lld hdev=%llu\n",
    + __func__, mean, stddev, average, tsc_deviation);

    return average;
    }
    --
    1.6.5.2


    \
     
     \ /
      Last update: 2009-12-15 05:13    [W:0.019 / U:60.724 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site