[uClinux-dev] Tiny memory

John Williams jwilliams at itee.uq.edu.au
Mon Mar 24 23:03:33 EST 2003

Yes it's me again,

With my timer interrupt apparently debugged now, I think I'm hitting the 
limits of my FPGA dev board only having 1M of RAM.

In start_kernel(), when calling kmem_cache_sizes_init() I'm getting

kmem_cache_create: couldn't create cache size-524288(DMA).
kernel BUG at slab.c:508!

At the top of slab.c are a bunch of crufty #ifdefs etc to set the cache 
slab sizes, and, well, since I've only got 1 meg total, and the kernel 
image takes about half of that, I obviously can't reserve a half-meg 
(and later, 1Meg) slab.

Am I interpreting this situation correctly?  Or should the cache 
initialisation routines see that there's not enough memory, and just not 
allocate those huge slabs (and thus there's something stranger going on 
in there)?

Realistically, is it time for me to get some more memory (my little baby 
is growing up so fast :) There's also 32MB of fairly fast DDR on this 
board, but I'll have to fiddle to get a controller up and running.

Or, should I maybe delay the inevitable a bit longer by munging the slab 
size stuff at the top of slab.c?



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