Messages in this thread |  | | | Date | Thu, 21 Feb 2008 11:44:06 +0100 | | From | Andi Kleen <> | | Subject | Re: [PATCH] Document huge memory/cache overhead of memory controller in Kconfig | |
> 1. We could create something similar to mem_map, we would need to handle 4
4? At least x86 mainline only has two ways now. flatmem and vmemmap.
> different ways of creating mem_map.
Well it would be only a single way to create the "aux memory controller
map" (or however it will be called). Basically just a call to single
function from a few different places.
> 2. On x86 with 64 GB ram,
First i386 with 64GB just doesn't work, at least not with default 3:1
split. Just calculate it yourself how much of the lowmem area is left
after the 64GB mem_map is allocated. Typical rule of thumb is that 16GB
is the realistic limit for 32bit x86 kernels. Worrying about
anything more does not make much sense.
> if we decided to use vmalloc space, we would need 64
> MB of vmalloc'ed memory
Yes and if you increase mem_map you need exactly the same space
in lowmem too. So increasing the vmalloc reservation for this is
equivalent. Just make sure you use highmem backed vmalloc.
-Andi
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