linux-kernel - Re: Is it possible to use ftrace to measure secondary CPU bootup time

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Date:   Wed, 26 Jul 2017 17:20:57 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Brandt, Todd E" <todd.e.brandt@...el.com>
Cc:     "Huang, Ying" <ying.huang@...el.com>,
        "Liu, Mengyang" <mengyang.liu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Is it possible to use ftrace to measure secondary CPU bootup
 time

On Mon, 24 Jul 2017 21:40:24 +0000
"Brandt, Todd E" <todd.e.brandt@...el.com> wrote:

> Function graph tracing is indeed the target, as its the basis of the bootgraph 
> tool. However, kprobes would work just as well. What's the difference in effort
> between enabling kprobes for early boot vs function graph trace?
> 

Hmm, good question. But then again, if you are only worried about
timings, tracing functions and looking at how long the next function
happens after the one you are interested in, should give you a good
idea of how long that function took.

If there is more interest, I could spend some time seeing if I can get
function graph tracing working early.

-- Steve