Re: [PATCH 08/19] mm: numa: Create basic numa page hinting infrastructure

[Rik van Riel]

On 11/06/2012 04:14 AM, Mel Gorman wrote:
> Note: This patch started as "mm/mpol: Create special PROT_NONE
> 	infrastructure" and preserves the basic idea but steals *very*
> 	heavily from "autonuma: numa hinting page faults entry points" for
> 	the actual fault handlers without the migration parts.	The end
> 	result is barely recognisable as either patch so all Signed-off
> 	and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with
> 	this version, I will re-add the signed-offs-by to reflect the history.
>
> In order to facilitate a lazy -- fault driven -- migration of pages, create
> a special transient PAGE_NUMA variant, we can then use the 'spurious'
> protection faults to drive our migrations from.
>
> Pages that already had an effective PROT_NONE mapping will not be detected

The patch itself is good, but the changelog needs a little
fix. While you are defining _PAGE_NUMA to _PAGE_PROTNONE on
x86, this may be different on other architectures.

Therefore, the changelog should refer to PAGE_NUMA, not
PROT_NONE.

> to generate these 'spurious' faults for the simple reason that we cannot
> distinguish them on their protection bits, see pte_numa(). This isn't
> a problem since PROT_NONE (and possible PROT_WRITE with dirty tracking)
> aren't used or are rare enough for us to not care about their placement.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>

Other than the changelog ...

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
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