[Arm-netbook] Debian boots in 0.87 seconds

[Luke Kenneth Casson Leighton]

On Tue, Dec 2, 2014 at 8:02 PM, peter green <plugwash at p10link.net> wrote:
> joem wrote:
>>
>> What about an open sourced script that can do this feat?
>> Everybody throws in their know how.
>>
>
> The problem is getting a fast boot time is really a matter of deciding what
> you can live without or at least start asyncronously after your main
> application has started, then ruthlessly optimising what is left for your
> specific case.
>
> So the result is a system that boots to a specific application very quickly
> but may be horriblly broken if the application or hardware used changes.

 there's a parallel init system i worked with that i adapted in 2006
to boot a 1.5ghz single-core pentium 3 system to x-windows in around
20 seconds.  shutdown was under *three* seconds.  instead of replacing
udev i split the udevadm startup into two "settle" sections: one
critical (disks, network, first 10 pseudo-ttys) and
one-for-everything-else.  x-windows and ssh were dependent on the
one-for-everything-else, and networking, disk mounting etc were
dependent on the critical one.

 the only problem you've got with parallel init systems is that they
rely on the processor being "modern" i.e. to have decent
context-switching.  an ARM9 is *NOT* a modern processor.  every
context-switch THROWS AWAY the cache.  a Cortex A7 / A9 we might have
better luck

 l.