This is about Linux
Posted Apr 7, 2006 9:59 UTC (Fri) by
kl (guest, #36963)
In reply to:
This is about Linux by nix
Parent article:
The Lessons of the $100 Laptop (eWeek)
> Migration and scheduler domains only get compiled in
> when you're SMP (and I think you need to say you're
> NUMA, too). I doubt your little tiny embedded body is
> a NUMA SMP box!
You are right of course. :)
But... in "traditional" embedded systems ASMP is not that
uncommon. It is rather The Way to achieve multiprocessing...
or was not that long time ago.
(ASMP is not SMP, but still MP...)
So forgive me, but for it wasn't that clear to me that there
are no tiny-(a)smp boxes. :]
(My background is rather 8051-like, so very different
from what I see in current embedded market.)
> I'm damn glad there's no way to disable syscalls: a faster
> way to break userspace doesn't easily come to mind (and,
> yes, so nobody uses e.g. unlinkat() *now*, but upgrade
> glibc to 2.4 and all of a sudden if you try to remove those
> 'new' syscalls, coreutils will break. You don't want that.
Yes, I don't, and any server/desktop machine doesn't want that.
On the other hand on embedded systems I don't use GLibc,
coreutils or similar things. I use uClibc, busybox, and the like.
Here, I see point of removing unused features like entirely new,
or entirely old system calls. I have impression that backwards
compatibility doesn't make any sense on these tiny systems,
where every bit counts...
> Equally, disabling subtree sharing, well, it might seem like
> a good idea, but how much memory does it actually use?
> Probably cleanups like unexporting symbols and fixing inlining
> and, hell, just compiling with -Os save a lot more space than
> disabling that ever would, and it's intrusive enough that
> trying to disable it without breaking sys_mount() or
> maintaining piles of duplicate code may just not be worth it.
I understand this perfectly. I'm just trying to point out that
Linux is not always best for _embedded_ systems.
New features added to kernel are often just useless for them.
On the other hand no one wants to implement things like PCI
support every time, so Linux gets choosen. And this is good,
because many people are working to make kernel smaller --
and more often their patches gets merged.
(I'm aware that my english is not without problems too so
I would like to apologize for that.)
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