Re: Embedded Linux Boot Time Poll

[Andrew Murray <amurray@mpcdata.com>]

Hi,

Thanks all for your very valuable input. This seems to be an
interesting topic that generates a lot of interest!

I've updated my statement - does this reflect your views?

"Given an unoptimised system based on embedded Linux with a clearly
defined purpose - The amount of boot time it takes to reach that
required state of functionality can be reduced by specialising the
software stack to those needs. Specialisation may involve
removing/deferring unrequired functionality/support and optimising
required functionality."

I've emphasised the focus of the statement to refer to a Linux based
system and so by doing this optimisation then refers to the system as
a whole including bootloaders, choice of filesystems, user space
initialisation, etc.

I've also defined boot time as the amount of time required to reach a
useful state of functionality - in other words meeting only the needs
of the application which provides the products purpose.

By remove functionality/support - I mean removing support for device
drivers not required and also removing unused functionality (which may
be things like removing kallsyms, ipautoconfig, printk support, etc).
And by 'optimise required functionality' - I think this can have a
broad meaning and include system design decisions such as how
userspace is initialised - e.g. the app could be the init process,
optimising flash timings, using a more optimal filesystem, removing
probes (if you know the hardware will always been there), etc.

And I've tried to use relative terms rather than absolute terms - so
the comparison is against an unoptimised system (e.g. perhaps a
customer has a pre-provided BSP and they have little knowledge of how
to optimise it and remove things via KConfig etc).

Thanks,

Andrew Murray

On 22 October 2010 00:20, Andrew Murray <amurray@mpcdata.com> wrote:
> Hello,
>
> I'm performing some research [for a CELF presentation] into reducing
> boot time on embedded systems and would like to see if the embedded
> community agree with the following statement as to why Linux
> [arguably] takes so long in the first place for an unoptimised system:
>
> "Linux is general purpose, convenient and flexible. As it's general
> purpose it's likely to contain un-required functionality which results
> in more initialisation and a larger image size. As it's convenient and
> flexible it will spent time discovering devices and verifying their
> existence."
>
> Do you largely agree or disagree?
> Also do you believe that boot time isn't the highest priority when it
> comes to improving the kernel?
>
> Thanks,
>
> Andrew Murray
>



-- 
Andrew Murray, Embedded Linux Group
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