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Message-Id: <1195670327.5294.24.camel@localhost>
Date: Wed, 21 Nov 2007 13:38:46 -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
On Wed, 2007-11-21 at 13:18 -0500, Lee Schermerhorn wrote:
> On Wed, 2007-11-21 at 13:12 -0500, Lee Schermerhorn wrote:
> > 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
>
> Never mind... I get it now. I was confusing zone ids with node ids.
>
However... [possibly another stupid question]
Don't the loops in {first|next}_zones_zonelist() depend on the zonelists
being in "zone order" as opposed to "node order". If the nodelists are
in node order, the lower zones can be interspersed with the upper zones,
I think. Looks like this would terminate the loops as soon as we hit a
lower zone, even tho' we might not have visited all of the nodes
represented in the zonelist.
Again, I could be missing some fine point of zonerefs that handles this
condition, but I can't see it.
Lee
> 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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