MIME-Version: 1.0
Date: Fri, 4 Apr 2014 00:02:21 -0700
Message-ID: <CAES_P+8kwWhaFoJPvvbDh6rJ0+VTpFutqUGefZmbghN21XtVdw@mail.gmail.com>
Subject: Query for time tracking between userspace and kernelspace
From: noman pouigt <variksla@gmail.com>
To: john.stultz@linaro.org, Thomas Gleixner <tglx@linutronix.de>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Michael Opdenacker <michael.opdenacker@free-electrons.com>,
        Joe Perches <joe@perches.com>, Petr Mladek <pmladek@suse.cz>,
        linux-kernel@vger.kernel.org, leiwen@marvell.com
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Sender: linux-kernel-owner@vger.kernel.org

Hello,

Probably this question belongs to kernelnewbies
list but I think i will get accurate answer from here.

I am doing some optimization in kernel video driver
code to reduce the latency from the time buffer
is given to the time it is displayed.

Userspace:
t1 = gettimeofday()

Kernelspace:
t2 = do_gettimeofday()

Using debugfs i am copying t2 to userspace and
subtracting the result.

latency = t2 - t1

Would this be accurate? I know there is context
switch involved and other stuff but this is the method
i came up with. Any better way?

System: ARM (Android)
Kernel- 3.10
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