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Date: Wed, 21 Nov 2007 13:12:27 -0500
From: Lee Schermerhorn <Lee.Schermerhorn@...com>
To: Mel Gorman <mel@....ul.ie>
Cc: clameter@....com, linux-kernel@...r.kernel.org,
kamezawa.hiroyu@...fujitsu.com, linux-mm@...ck.org
Subject: Re: [PATCH 5/6] Have zonelist contains structs with both a zone
pointer and zone_idx
Mel:
Are the comparisons noted below correct--i.e., '>' rather than '<'? I'm
trying to understand how this matches the comments and code. Doesn't
look right to me, but I could be missing something.
Lee
On Wed, 2007-11-21 at 00:40 +0000, Mel Gorman wrote:
> Filtering zonelists requires very frequent use of zone_idx(). This is costly
> as it involves a lookup of another structure and a substraction operation. As
> the zone_idx is often required, it should be quickly accessible. The node
> idx could also be stored here if it was found that accessing zone->node is
> significant which may be the case on workloads where nodemasks are heavily
> used.
>
> This patch introduces a struct zoneref to store a zone pointer and a zone
> index. The zonelist then consists of an array of these struct zonerefs which
> are looked up as necessary. Helpers are given for accessing the zone index
> as well as the node index.
>
> [kamezawa.hiroyu@...fujitsu.com: Suggested struct zoneref instead of embedding information in pointers]
> Signed-off-by: Mel Gorman <mel@....ul.ie>
> Acked-by: Christoph Lameter <clameter@....com>
> Acked-by: David Rientjes <rientjes@...gle.com>
> ---
>
> arch/parisc/mm/init.c | 2 -
> fs/buffer.c | 6 ++--
> include/linux/mmzone.h | 64 ++++++++++++++++++++++++++++++++++++------
> include/linux/oom.h | 4 +-
> kernel/cpuset.c | 4 +-
> mm/hugetlb.c | 3 +-
> mm/mempolicy.c | 36 ++++++++++++++----------
> mm/oom_kill.c | 45 ++++++++++++++----------------
> mm/page_alloc.c | 66 ++++++++++++++++++++++++--------------------
> mm/slab.c | 2 -
> mm/slub.c | 2 -
> mm/vmscan.c | 6 ++--
> 12 files changed, 149 insertions(+), 91 deletions(-)
>
<snip>
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-010_use_two_zonelists/include/linux/mmzone.h linux-2.6.24-rc2-mm1-020_zoneid_zonelist/include/linux/mmzone.h
> --- linux-2.6.24-rc2-mm1-010_use_two_zonelists/include/linux/mmzone.h 2007-11-20 23:27:04.000000000 +0000
> +++ linux-2.6.24-rc2-mm1-020_zoneid_zonelist/include/linux/mmzone.h 2007-11-20 23:27:34.000000000 +0000
> @@ -469,6 +469,15 @@ struct zonelist_cache;
> #endif
>
> /*
> + * This struct contains information about a zone in a zonelist. It is stored
> + * here to avoid dereferences into large structures and lookups of tables
> + */
> +struct zoneref {
> + struct zone *zone; /* Pointer to actual zone */
> + int zone_idx; /* zone_idx(zoneref->zone) */
> +};
> +
> +/*
> * One allocation request operates on a zonelist. A zonelist
> * is a list of zones, the first one is the 'goal' of the
> * allocation, the other zones are fallback zones, in decreasing
> @@ -476,11 +485,18 @@ struct zonelist_cache;
> *
> * If zlcache_ptr is not NULL, then it is just the address of zlcache,
> * as explained above. If zlcache_ptr is NULL, there is no zlcache.
> + * *
> + * To speed the reading of the zonelist, the zonerefs contain the zone index
> + * of the entry being read. Helper functions to access information given
> + * a struct zoneref are
> + *
> + * zonelist_zone() - Return the struct zone * for an entry in _zonerefs
> + * zonelist_zone_idx() - Return the index of the zone for an entry
> + * zonelist_node_idx() - Return the index of the node for an entry
> */
> -
> struct zonelist {
> struct zonelist_cache *zlcache_ptr; // NULL or &zlcache
> - struct zone *zones[MAX_ZONES_PER_ZONELIST + 1]; // NULL delimited
> + struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
> #ifdef CONFIG_NUMA
> struct zonelist_cache zlcache; // optional ...
> #endif
> @@ -713,26 +729,52 @@ extern struct zone *next_zone(struct zon
> zone; \
> zone = next_zone(zone))
>
> +static inline struct zone *zonelist_zone(struct zoneref *zoneref)
> +{
> + return zoneref->zone;
> +}
> +
> +static inline int zonelist_zone_idx(struct zoneref *zoneref)
> +{
> + return zoneref->zone_idx;
> +}
> +
> +static inline int zonelist_node_idx(struct zoneref *zoneref)
> +{
> +#ifdef CONFIG_NUMA
> + /* zone_to_nid not available in this context */
> + return zoneref->zone->node;
> +#else
> + return 0;
> +#endif /* CONFIG_NUMA */
> +}
> +
> +static inline void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
> +{
> + zoneref->zone = zone;
> + zoneref->zone_idx = zone_idx(zone);
> +}
> +
> /* Returns the first zone at or below highest_zoneidx in a zonelist */
> -static inline struct zone **first_zones_zonelist(struct zonelist *zonelist,
> +static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
> enum zone_type highest_zoneidx)
> {
> - struct zone **z;
> + struct zoneref *z;
>
> /* Find the first suitable zone to use for the allocation */
> - z = zonelist->zones;
> - while (*z && zone_idx(*z) > highest_zoneidx)
> + z = zonelist->_zonerefs;
> + while (zonelist_zone_idx(z) > highest_zoneidx)
!!! HERE: ^
> z++;
>
> return z;
> }
>
> /* Returns the next zone at or below highest_zoneidx in a zonelist */
> -static inline struct zone **next_zones_zonelist(struct zone **z,
> +static inline struct zoneref *next_zones_zonelist(struct zoneref *z,
> enum zone_type highest_zoneidx)
> {
> /* Find the next suitable zone to use for the allocation */
> - while (*z && zone_idx(*z) > highest_zoneidx)
> + while (zonelist_zone_idx(z) > highest_zoneidx)
!!! and HERE: ^
> z++;
>
> return z;
> @@ -748,9 +790,11 @@ static inline struct zone **next_zones_z
> * This iterator iterates though all zones at or below a given zone index.
> */
> #define for_each_zone_zonelist(zone, z, zlist, highidx) \
> - for (z = first_zones_zonelist(zlist, highidx), zone = *z++; \
> + for (z = first_zones_zonelist(zlist, highidx), \
> + zone = zonelist_zone(z++); \
> zone; \
> - z = next_zones_zonelist(z, highidx), zone = *z++)
> + z = next_zones_zonelist(z, highidx), \
> + zone = zonelist_zone(z++))
>
> #ifdef CONFIG_SPARSEMEM
> #include <asm/sparsemem.h>
<snip>
-
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