[U-Boot] RE : Reduce time to load

[Wolfgang Denk <wd@denx.de>]

Dear Simon,

In message <51D9710FF5643747BB605F97B8DE56CD0231C16E@STEGOSAURE.adetel.com> you wrote:
> 
> U-boot take about 2 seconds to load the kernel.

That sounds resonable, depending on the device you load Linux from.

> The rest of the system take about 10 seconds until I get the prompt, so

10 seconds is a lot. I bet you use slow and/or big root file system, then.

And how long does it take to start the real application, then?

> it represents ~16% of total time needed to have an operational system.
> I agree to say that most of the work to reduce boot time have to be done
> on the kernel and userspace, but I'm trying to save as much time as
> possible, even if it's 100ms.

Well, trace the execution (for example by simply timestamping the
messages printed by U-Boot - expect comes in handy to do that), and
find out which poarts in U-Boot contribute most to these 2 seconds.

The old rules that always apply are: you can trade off reliability
for speed (like switching off image checksumming by setting the
"verify" variable to "no"), and you can trade off cose (like flash
memory foorprint) for speed (like using an uncompressed ext2 file
system in a MTD device, preferrably on NOR flash). See the DULG for
root file system selection, etc.

Best regards,

Wolfgang Denk

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