Re: discontig patch question

[jbarnes@sgi.com (Jesse Barnes)]

On Mon, Nov 10, 2003 at 09:52:49AM -0600, Van Maren, Kevin wrote:
> The EFI memory map is simple, and looks like:
>  0- 4G Node 0 (2G + 2G hole)
>  4- 8G Node 1
>  8-12G Node 2
> 12-16G Node 3
> 16-20G Node 0 (2 G memory-map I/O reclaim)
> with 4G per node, 16GB total.
> 
> Because of ORDERROUNDDOWN in count_pages (arch/ia64/mm/init.c),
> the memory ended up being assigned like this:
> 
>  0- 8G Node 1 (6G, 2GB hole)
>  8-16G Node 3 (8G)
> 16-20G Node 0 (2G)
>        Node 2 (0G)
> 
> Which was not at all what I wanted.

I guess I didn't see this because the nodes on sn2 are so large (64GB).

> ORDERROUNDDOWN causes the kernel to assign all memory starting at the
> (PAGE_SIZE << MAX_ORDER) boundary to the current node, which in my case
> is 16KB << 19 (hard-coded for IA64), or 8GB.

I wonder if that shouldn't be simply 1UL<<MAX_ORDER...  That's all that
mm/page_alloc.c seems to care about.

> I understand the GRANULE rounding, but is there a compelling reason that
> we need 8GB node chunks on IA64 Linux (with 16KB pages)?

I don't think so.

Jesse