Re: [ECOS] Memory Footprint

[Jonathan Larmour <jlarmour at redhat dot com>]

> "Reto.Bucher@elektrobit.ch" wrote:
> 
> Hello!
> 
> I'm currently evaluating different operating systems for embedded
> systems. Therefore, memorysize is one major concern.
> 
> + What minimal size of memory footprint can I expect when I need to
> include a TCP/IP stack?

Here's something I wrote before for the ARM:

-=-=-=-=-=-=-=-
>From some simple measurements, the difference between including and not
including the stack appears to be about 121944 bytes code, 3944 bytes
initialized data, and 296940 bytes BSS, 256K of which is networking
buffers.

The buffer size cannot be shrunk down to near 0 though. Hugo would know
better what the minimal requirements for this are. I've quoted below some
things he wrote before that indicate that 128K is almost certainly the
absolute minimum, otherwise you may never receive 64K packets. So you can
subtract 128K off that 296940 bytes BSS to give the minimum. And as he
says, there will potentially be more overruns/lost data even with that
minimum.

This is for an app that includes read, write and select. Values may differ
more with extra functions as large sections of the stack may be brought in
due to selective linking. But probably not.
-=-=-=-=-=-=-=-

eCos needs very little above that.
 
> + is eCos a hard real time system?

No, it is soft real time. The reasoning is that a lot of people believe
they want a hard real time system, when they actually don't require it
(hard real time systems while more deterministic, tend to be a lot slower).

Jifl
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