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Subject: Re: Benchmarks of kernel tracing options 2 (ftrace, lttng and perf)
From: Steven Rostedt <rostedt@goodmis.org>
To: David Sharp <dhsharp@google.com>
Cc: Douglas Santos <douglas.santos@polymtl.ca>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "ltt-dev@lists.casi.polymtl.ca" <ltt-dev@lists.casi.polymtl.ca>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
        Michael Rubin <mrubin@google.com>
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Date: Wed, 17 Nov 2010 18:33:02 -0500
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On Wed, 2010-11-17 at 15:22 -0800, David Sharp wrote:
> 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)?

Oops, no, I was thinking that this was from your tests. I remember
asking you to try the new kernel. I think I got you and Douglas
confused :-)

-- Steve