Re: Memory Rusting Effect [re: Linux hostile to poverty]

David Luyer (luyer@ucs.uwa.edu.au)
Mon, 20 Jul 1998 17:09:20 +0800

> > Folks, increased functionality and/or increased performance almost always
> > means increased memory footprint. There's no fix for that yet, as long as
> > the kernel itself can't be swapped (and I don't think we want to deal with
> > the *nasty* potential deadlocks inherent in swappable kernel memory!).
>
> I think people exaggerate how hard that is. I've had bits of this sort of
> working in 2.1.x earlier. So long as you only touch interface code that
> is not itself involved in swapping and which can tolerate sleeping - of
> which much of the config side code is an obvious candidate then you can
> merge it all together by borrowing the initfunc trick and having
>
> __swappable(int somedev_complexioctl(...))

As long as this is an option or doesn't add too much to the kernel code, as
it is a 'wasteful extra' on NFS-root or flash booting embedded systems with
no swap.

I'd like to see config options for a minimal Linux, maybe even options which
violate POSIX or remove some security for the sake of saving on code.

Examples of things which can go for some embedded systems but AFAIK aren't
options;
* all swap code
* possibly /dev/random
* complete removal of immutable, append-only
* complete removal of atime (replace with pad field)
* printk() and kernel logs?
* capabilities
* dcache?
* groups? (with a big warning about the effect of this)
and so on...

Maybe a menu in menuconfig called 'embedded systems options' which gives
options to disable some of these fundamental items and warns of the dangers
of doing so.

David.

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