Hello Robert
Hopefully, I still can help you...
right, but what is the formula that determines how *much* of RAM is
allocated for that vmalloc area?
IMHO, no formula. As long as they fit into VMALLOC adress range and
there are free pages, you can allocate as many as you need. Notice that
vmalloc is just a way to allocate non contigous pages and make them
virtually contigous.
so far, so good. but if i move to another system that has only 512M
of RAM, i read from the same places:
...
MemTotal: 448928 kB
...
VmallocTotal: 573432 kB
^^^^^^^^^^^^^^^^^^^^^^^^^^^^ are you sure about that? hm , all are
vmalloc()-ed? possible, but weird for me.
so with only 512M of RAM, clearly i can't use all of that for the
"NORMAL" zone since some of it has to be reserved for kernel tables
that normally reside in "high" memory, right?
yeah, they do need space.
i'm just trying to get straight the algorithm the kernel uses to
allocate what RAM i have to the various zones, and what that space
will eventually be used for.
I think that really depends on how kernel developer decides the weight
factor of pressures that happen toward each zones. IMSO (In My Stupid
Opinion), certainly DMA zone should be less occupied, because DMA
operation needs them badly. Then, instead of pressing NORMAL zone, if
the pages aren't so frequently accessed or could be accessed in non
atomic style, HIGHMEM zone is perfect choice. So the order is, stomp
HIGHMEM first, then NORMAL, finally DMA zone. I hope this is what you ask.
sadly, the phrase "logical address" is already in common use to refer
to those offset-based addresses, as opposed to the addresses that
actually use the kernel page tables.
OK... well then, I hope I help you...
regards,
Mulyadi
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