On Tue, 11 Sep 2007 22:31:27 +0100 (IST)
Mel Gorman <[email protected]> wrote:
> Using two zonelists per node requires very frequent use of zone_idx(). This
> is costly as it involves a lookup of another structure and a substraction
> operation. As struct zone is always word aligned and normally cache-line
> aligned, the pointer values have a number of 0's at the least significant
> bits of the address.
>
> This patch embeds the zone_id of a zone in the zonelist->zones pointers.
> The real zone pointer is retrieved using the zonelist_zone() helper function.
> The ID of the zone is found using zonelist_zone_idx(). To avoid accidental
> references, the zones field is renamed to _zones and the type changed to
> unsigned long.
>
At first, I welcome this patch. thanks!.
A comment after reading all is, how about defining zonelist as following
instead of encoding in pointer ?
==
struct zone_pointer {
struct zone *zone;
int node_id;
int zone_idx;
};
struct zonelist {
struct zone_pointer _zones[MAX_ZONES_PER_ZONELIST + 1];
};
#define zonelist_zone(zl) (zl)->zone
#define zonelist_zone_idx(zl) (zl)->zone_idx
#ifdef CONFIG_NUMA
#define zonelist_zone_nid(zl) (zl)->node_id
#else
#define zonelist_zone_nid(zl, i) (0)
==
If we really want to avoid unnecessary access to "zone" while walking zonelist,
above may do something good. Cons is this makes sizeof zonlist bigger.
Thanks,
-Kame
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