Re: [PATCH 0/3] [RFC] init, tracing: Add initcall trace events

[Andrew Morton]

On Fri, 23 Mar 2018 11:02:41 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> 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?