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Date: Fri, 23 Mar 2018 12:50:16 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Abderrahmane Benbachir <abderrahmane.benbachir@polymtl.ca>,
        =?ISO-8859-1?Q?Am=C3=A9rico?= Wang <xiyou.wangcong@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 0/3] [RFC] init, tracing: Add initcall trace events
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On Fri, 23 Mar 2018 11:02:41 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:

> A while ago we had a boot tracer. But it was eventually removed:
>  commit 30dbb20e68e6f ("tracing: Remove boot tracer").
> 
> The rational was because there is already a initcall_debug boot option
> that causes printk()s of all the initcall functions.

"rationale" :)

> The problem with the initcall_debug option is that printk() is awfully slow,
> and makes it difficult to see the real impact of initcalls. Mainly because
> a single printk() is usually slower than most initcall functions.

Not understanding this.  We do it correctly:

	calltime = ktime_get();
	ret = fn();
	rettime = ktime_get();

so the displayed initcall timing is independent of the printk()
execution time?