lkml.org 
[lkml]   [2003]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] documentation for basic guide to profiling
    On Fri, Feb 28, 2003 at 12:12:42AM -0800, Martin J. Bligh wrote:

    > +Readprofile
    > +-----------
    > +get readprofile binary fixed for 2.5 / akpm's 2.5 patch from
    > +ftp://ftp.kernel.org/pub/linux/people/mbligh/tools/readprofile/
    > +add "profile=2" to the kernel command line.
    > +
    > +clear echo 2 > /proc/profile

    As far as I can see, the 2 is meaningless here. This should just be

    echo > /proc/profile

    (On SMP when writing sizeof(int) bytes, the value written
    is significant. But 1 or 2 is not sizeof(int).)

    Andries

    -----
    Fragment of some notes:

    <sect1>Profiling the kernel<p>
    There are several facilities to see where the kernel spends
    its resources. A simple one is the profiling function, that
    stores the current EIP (instruction pointer) at each clock tick.
    <p>
    Boot the kernel with command line option <tt>profile=2</tt>
    (or some other number instead of 2). This will cause
    a file <tt>/proc/profile</tt> to be created.
    The number given after <tt>profile=</tt> is the number of positions
    EIP is shifted right when profiling. So a large number gives a
    coarse profile.
    The counters are reset by writing to <tt>/proc/profile</tt>.
    The utility <tt>readprofile</tt> will output statistics for you.
    It does not sort - you have to invoke <tt>sort</tt> explicitly.
    But given a memory map it will translate addresses to kernel symbols.
    <p>
    See <tt>kernel/profile.c</tt> and <tt>fs/proc/proc_misc.c</tt>
    and <tt>readprofile(1)</tt>.
    <p>
    For example:
    <verb>
    # echo > /proc/profile
    ...
    # readprofile -m System.map-2.5.59 | sort -nr | head -2
    510502 total 0.1534
    508548 default_idle 10594.7500
    </verb>
    -
    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 13:33    [W:3.885 / U:0.724 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site