linux-kernel - Re: unwind_init() takes 100 ms

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Date:   Tue, 9 Oct 2018 08:13:01 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: unwind_init() takes 100 ms


* Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Mon, Oct 08, 2018 at 12:34:17PM -0500, Josh Poimboeuf wrote:
> > > 4.  Would a command line parameter be reasonable `disable_unwind`, so people
> > > could decrease their boot time with distribution kernels, and easily turn it
> > > back on, when they need a stacktrace without having to rebuild the Linux
> > > kernel?
> > 
> > I think a boot cmdline option to disable ORC would be ok.  However,
> > disabling ORC would need to fall back to the "guess" unwinder.
> > Otherwise it would make debugging impossible.  That shouldn't be too
> > hard, but it would require restructuring the code a bit.
> 
> But I should also clarify that this option wouldn't be worth it.
> Sorting at build time is the way to go.

Yep, very much so.

Thanks,

	Ingo