Date: Mon, 22 Dec 2014 16:53:12 -0700 From: Ian Lepore <ian@freebsd.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: current@freebsd.org Subject: Re: simple task to speed up booting Message-ID: <1419292392.1018.132.camel@freebsd.org> In-Reply-To: <22181.1419261352@critter.freebsd.dk> References: <43445.1418553160@critter.freebsd.dk> <1419224743.1018.108.camel@freebsd.org> <22181.1419261352@critter.freebsd.dk>
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On Mon, 2014-12-22 at 15:15 +0000, Poul-Henning Kamp wrote:
> --------
> In message <1419224743.1018.108.camel@freebsd.org>, Ian Lepore writes:
>
> >On Sun, 2014-12-14 at 10:32 +0000, Poul-Henning Kamp wrote:
> >> The rotating swirlie ('-/|\') in the loader accounts for a surprisingly
> >> large part of our boot time on systems with slow-ish serial consoles.
> >>
> >I investigated this a bit today. I instrumented the loader on arm to
> >count how many times twiddle() is called while loading a 5.5MB kernel.
> >When loading over NFS it was called 5580 times. When loading from an
> >sdcard it was called 284 times.
>
> It would be plenty if it twiddled once per second, in fact it would
> probably be much better if it *only* twiddled once per second, because
> the at least people could count the steps and gain some idea where
> in the process the problem is.
>
Unfortunately we can't count on the availability of a useful clock in a
libstand environment.
> >So all in all it seems like different kinds of IO need different
> >throttling, something like the attached (which also still has some stats
> >output in it). I can't decide if it's worth committing... it'll have a
> >lot of value to someone with slow serial and netbooting, is that common?
>
> How about a compile time "global" divisor so people can reduce it
> even further ?
>
Rather than compile-time I made it a run-time setting by adding a
twiddle_divisor variable to loader(8). r276079 and r276087.
-- Ian
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