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SubjectRe: [RFC] Simplify node/zone portion of page->flags
Matthew Dobson <> wrote:
> Currently we keep track of a pages node & zone in the top 8 bits (on
> 32-bit arches, 10 bits on 64-bit arches) of page->flags. We typically
> do: node_num * MAX_NR_ZONES + zone_num = 'nodezone'. It's non-trivial
> to break this 'nodezone' back into node and zone numbers. This patch
> modifies the way we compute the index to be: (node_num << ZONE_SHIFT) |
> zone_num. This makes it trivial to recover either the node or zone
> number with a simple bitshift. There are many places in the kernel
> where we do things like: page_zone(page)->zone_pgdat->node_id to
> determine the node a page belongs to. With this patch we save several
> pointer dereferences, and it boils down to shifting some bits.

This rather conflicts with the patch from Jesse which I have. Can you guys
work that out and let me know when you're done?

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