[U-Boot-Users] decrease boot time

Wolfgang Denk
2005-02-12T22:30:21Z

In message <528646bc05021213026ed990ce@mail.gmail.com> you wrote:
>
> You think? If possible; I would get some hard numbers on your boot
> sequence and find out for sure. You could use a serial protocol
> analyser to attach timestamps to the boot logs. Make sure you're
> optimizing the right things.

You can do this even without hardware support. Attached below is a
trivial expect script which you can use to pipe the output of your
terminal program into to get it timestamped. this is not perfect (as
it timestamps on the _eond_ of each line), but does it's job in 95%
of all cases. See the comment in the script for ow to use it.

> > In u-boot I can switch on the MMU and cache also, is this simply working
> > by enabling the two CONFIG defines?

Nothing is ever "simply working". You have to understand what you are
doing. Reading the README helps.

> I cannot comment on u-boot and the cache, but in the kernel the cache
> is turned on before decompression. Look in

U-Boot always turns on the instruction cache; the conditions for
using the data cache are processor dependent - always off on some
systems (8xx) or always on on others (like 8240 for example).

> > I agree fully. But for now our customer is upset about the 3 seconds to
> > boot prompt and we promised him to boot in one second.

It is wise to first measure what you can get before making such
promises :-)

> > Well, I tried the console parameter "quiet" of linux to figure out how
> > exepensive in time the console output really is. Booting lastst 2.8s
> > instead of 3.1s than. So it is not much, but a bit, since initialing of
> > the serial stuff would be omitted.

This depends on the baud rate, of course. 0.1 ... 0.2 seconds is what
I see, too - for 115200 bps.

BTW - did you consider XIP??

It's off topic here (like most of this ;-) but for the sake of
completeness: see also

http://tree.celinuxforum.org/CelfPubWiki/BootupTimeWorkingGroup
and
http://tree.celinuxforum.org/CelfPubWiki/TechConference2005Docs?action=AttachFile&do=get&target=BTWG-Discussion-Plenary2005.pdf

Best regards,

Wolfgang Denk

--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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