lkml.org 
[lkml]   [2010]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: Benchmarks of kernel tracing options 2 (ftrace, lttng and perf)
    On Wed, Nov 17, 2010 at 2:56 PM, Douglas Santos
    <douglas.santos@polymtl.ca> wrote:
    > Quoting Steven Rostedt <rostedt@goodmis.org>:
    >> On Wed, 2010-11-17 at 16:31 -0500, Douglas Santos wrote:
    >> > Hi all,
    >> >
    >> > This is a response to a benchmark, submitted a few weeks ago, comparing
    >> kernel
    >> > tracing options.
    >> > http://lkml.org/lkml/2010/10/28/422
    >> >
    >> > We followed the methodology described in the link bellow,
    >> > but using the shellscripts posted there to reproduce autotest scripts.
    >> > http://lkml.org/lkml/2010/10/28/261
    >> >
    >> > We disabled the extra syscall tracing on lttng, for a fair comparison.
    >> > http://lkml.org/lkml/2010/10/28/290
    >> >
    >> > Average results with tracing "on":
    >> >
    >> > lttng:  220 ns
    >> > ftrace: 260 ns
    >>
    >> Heh, so ftrace got worse with the new kernel?

    Steve, can you explain how you're drawing that conclusion? Did Douglas
    run this benchmark before on a previous kernel (I didn't see it if
    so)?

    - You can't directly compare to my results because of different hardware.
    - The methodology for lttng is different (syscall tracing was removed).
    - My results were also on 2.6.36

    > The previous bench was doing tracing "on" minus "off"
    > average results. They also used autotest scripts, not sure if
    > it does exactly the same thing.

    I think the subtraction is important, or it is at least important to
    see what the "off" result is as a baseline of comparison. Otherwise, a
    huge portion of the measurement is the cost of making the syscall
    itself.

    >
    > I'll check if we missed something.
    >
    >
    >
    --
    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: 2010-11-18 00:25    [W:0.024 / U:2.592 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site