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

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Message-ID: <20181008173614.bchqq6unw65bc57x@treble>
Date:   Mon, 8 Oct 2018 12:36:14 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     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

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.

-- 
Josh