lkml.org 
[lkml]   [2002]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: Periodic clock tick considered harmful (was: Re: HZ, preferably as
    Date
    From
    > First blush is HELL YES!  The issue is accounting.  When you
    > ask how long a program ran, you are looking at the
    > accounting that happens on a tick. This is where one of two

    Thats also an implementation issue. Note that the current code is also
    wildly inaccurate. Mr Shannon says we are good to at best 50 run/sleep
    changes a second. I've got "100% busy" workloads that are 99% asleep.

    Tracking cpu usage at task switch works a lot better for newer processors
    which as well as having rdtsc also have performance counters. In fact you
    can do much more interesting things on modern PC class platforms like
    scheduling using pre-emption interrupts based on instructions executed,
    memory accesses and more.

    Alan
    -
    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: 2005-03-22 13:27    [W:3.544 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site