From: Steven Rostedt <rostedt@goodmis.org>
To: Chase Douglas <chase.douglas@canonical.com>
Cc: linux-kernel@vger.kernel.org,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH] ftrace: print sample std dev when function profiling
Date: Tue, 27 Apr 2010 16:50:02 -0400 [thread overview]
Message-ID: <1272401402.9739.77.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <1272304925-2436-1-git-send-email-chase.douglas@canonical.com>
On Mon, 2010-04-26 at 14:02 -0400, Chase Douglas wrote:
> + /* Sample standard deviation (s^2) */
> + if (rec->counter <= 1)
> + stddev = 0;
> + else {
> + stddev = rec->time_squared - rec->counter * avg * avg;
> + do_div(stddev, (rec->counter - 1) * 1000); /* ns^2 -> us^2 */
Shouldn't this be:
do_div(stddev, (rec->counter - 1) * 1000000); ?
(x / 1000)^2 == x^2 / 1000^2
-- Steve
> + }
> +
next prev parent reply other threads:[~2010-04-27 20:50 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-26 18:02 Chase Douglas
2010-04-27 20:50 ` Steven Rostedt [this message]
2010-04-27 21:06 ` Chase Douglas
2010-04-27 22:15 ` Steven Rostedt
2010-04-30 8:47 ` [tip:tracing/core] tracing: Show sample std dev in " tip-bot for Chase Douglas
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