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SubjectRe: [PATCH 14/40] autonuma: add page structure fields
On 06/28/2012 08:55 AM, Andrea Arcangeli wrote:
> On 64bit archs, 20 bytes are used for async memory migration (specific
> to the knuma_migrated per-node threads), and 4 bytes are used for the
> thread NUMA false sharing detection logic.
>
> This is a bad implementation due lack of time to do a proper one.

It is not ideal, no.

If you document what everything does, maybe somebody else
will understand the code well enough to help fix it.

> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -136,6 +136,32 @@ struct page {
> struct page *first_page; /* Compound tail pages */
> };
>
> +#ifdef CONFIG_AUTONUMA
> + /*
> + * FIXME: move to pgdat section along with the memcg and allocate
> + * at runtime only in presence of a numa system.
> + */

Once you fix it, could you fold the fix into this patch?

> + /*
> + * To modify autonuma_last_nid lockless the architecture,
> + * needs SMP atomic granularity< sizeof(long), not all archs
> + * have that, notably some ancient alpha (but none of those
> + * should run in NUMA systems). Archs without that requires
> + * autonuma_last_nid to be a long.
> + */
> +#if BITS_PER_LONG> 32
> + int autonuma_migrate_nid;
> + int autonuma_last_nid;
> +#else
> +#if MAX_NUMNODES>= 32768
> +#error "too many nodes"
> +#endif
> + /* FIXME: remember to check the updates are atomic */
> + short autonuma_migrate_nid;
> + short autonuma_last_nid;
> +#endif
> + struct list_head autonuma_migrate_node;
> +#endif

Please document what these fields mean.


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