Re: ucLinux and XIP memory savings

Hi Larry,

Thanks for your response.

> Subject: Re: [uClinux-dev] ucLinux and XIP memory savings
> 
> Anna,
> 
> It is a national holiday in the US, so I am out of the office until
> Monday when I will be able to send you more details.
> 
> I tried to use a Lantronix EDS2100 for an RS-232 data-logging
> application with remote access.  That box has an M68K ColdFire
> processor, 8MB RAM, 8 MB flash.  I used XIP and any other technique I
> could find to increase RAM.  The biggest headache was the Linux 2.6
> power-of-2 buddy system memory allocator.  I guess in the 2.4 kernel,
> there was a boxcar memory allocator.  That would have been better for
> such a small memory system.  I had to resort to fixing GCC to try to
> catch stack overflow problems in standard apps (NTP, for time -- no
> RTC).  But, I ran out of time to get the system to run reliably -- it
> kept locking up because of memory allocation failures due to the power-
> of-2 memory allocation scheme.

Is this really still true? I had read somewhere that it is possible to replace the standard kernel memory allocator under ucLinux with one that is better suited to embedded systems, e.g. a block-based memory pool type allocator. I cannot find the reference anymore now though.

Also, I found in the kernel documentation that in the no-MMU configuration you can disable power-of-2 round-ups by setting sysctl `vm.nr_trim_pages' to 0. This would allow finer-grained memory allocation and help limit fragmentation. 

I haven't used any of these myself, so any guidance on the suitability of those configuration options would be great.
 
Thanks,
Anna
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