Re: [PATCH] Document huge memory/cache overhead of memory controllerin Kconfig
From: Andi Kleen
Date: Thu Feb 21 2008 - 05:42:39 EST
> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/