lkml.org 
[lkml]   [2006]   [Jun]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: More weird latency trace output (was Re: 2.6.17-rt1)
    From
    Date
    On Wed, 2006-06-21 at 22:51 -0400, Lee Revell wrote:
    > How can the latency tracer be reporting 1898us max latency while the
    > trace is of a 12us latency? This must be a bug, correct?

    I've found the bug. The latency tracer uses get_cycles() for
    timestamping, which uses rdtsc, which is unusable for timing on dual
    core AMD64 machines due to the well known "unsynced TSCs" hardware bug.

    Would a patch to convert the latency tracer to use gettimeofday() be
    acceptable?

    Lee

    -
    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: 2006-06-23 03:27    [W:3.642 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site