*/
#define DEF_PRIORITY 12
+/* Maximum number of zones on a zonelist */
+#define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
+
+#ifdef CONFIG_NUMA
+/*
+ * We cache key information from each zonelist for smaller cache
+ * footprint when scanning for free pages in get_page_from_freelist().
+ *
+ * 1) The BITMAP fullzones tracks which zones in a zonelist have come
+ * up short of free memory since the last time (last_fullzone_zap)
+ * we zero'd fullzones.
+ * 2) The array z_to_n[] maps each zone in the zonelist to its node
+ * id, so that we can efficiently evaluate whether that node is
+ * set in the current tasks mems_allowed.
+ *
+ * Both fullzones and z_to_n[] are one-to-one with the zonelist,
+ * indexed by a zones offset in the zonelist zones[] array.
+ *
+ * The get_page_from_freelist() routine does two scans. During the
+ * first scan, we skip zones whose corresponding bit in 'fullzones'
+ * is set or whose corresponding node in current->mems_allowed (which
+ * comes from cpusets) is not set. During the second scan, we bypass
+ * this zonelist_cache, to ensure we look methodically at each zone.
+ *
+ * Once per second, we zero out (zap) fullzones, forcing us to
+ * reconsider nodes that might have regained more free memory.
+ * The field last_full_zap is the time we last zapped fullzones.
+ *
+ * This mechanism reduces the amount of time we waste repeatedly
+ * reexaming zones for free memory when they just came up low on
+ * memory momentarilly ago.
+ *
+ * The zonelist_cache struct members logically belong in struct
+ * zonelist. However, the mempolicy zonelists constructed for
+ * MPOL_BIND are intentionally variable length (and usually much
+ * shorter). A general purpose mechanism for handling structs with
+ * multiple variable length members is more mechanism than we want
+ * here. We resort to some special case hackery instead.
+ *
+ * The MPOL_BIND zonelists don't need this zonelist_cache (in good
+ * part because they are shorter), so we put the fixed length stuff
+ * at the front of the zonelist struct, ending in a variable length
+ * zones[], as is needed by MPOL_BIND.
+ *
+ * Then we put the optional zonelist cache on the end of the zonelist
+ * struct. This optional stuff is found by a 'zlcache_ptr' pointer in
+ * the fixed length portion at the front of the struct. This pointer
+ * both enables us to find the zonelist cache, and in the case of
+ * MPOL_BIND zonelists, (which will just set the zlcache_ptr to NULL)
+ * to know that the zonelist cache is not there.
+ *
+ * The end result is that struct zonelists come in two flavors:
+ * 1) The full, fixed length version, shown below, and
+ * 2) The custom zonelists for MPOL_BIND.
+ * The custom MPOL_BIND zonelists have a NULL zlcache_ptr and no zlcache.
+ *
+ * Even though there may be multiple CPU cores on a node modifying
+ * fullzones or last_full_zap in the same zonelist_cache at the same
+ * time, we don't lock it. This is just hint data - if it is wrong now
+ * and then, the allocator will still function, perhaps a bit slower.
+ */
+
+
+struct zonelist_cache {
+ DECLARE_BITMAP(fullzones, MAX_ZONES_PER_ZONELIST); /* zone full? */
+ unsigned short z_to_n[MAX_ZONES_PER_ZONELIST]; /* zone->nid */
+ unsigned long last_full_zap; /* when last zap'd (jiffies) */
+};
+#else
+struct zonelist_cache;
+#endif
+
/*
* 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
* priority.
*
- * Right now a zonelist takes up less than a cacheline. We never
- * modify it apart from boot-up, and only a few indices are used,
- * so despite the zonelist table being relatively big, the cache
- * footprint of this construct is very small.
+ * 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.
*/
+
struct zonelist {
- struct zone *zones[MAX_NUMNODES * MAX_NR_ZONES + 1]; // NULL delimited
+ struct zonelist_cache *zlcache_ptr; // NULL or &zlcache
+ struct zone *zones[MAX_ZONES_PER_ZONELIST + 1]; // NULL delimited
+#ifdef CONFIG_NUMA
+ struct zonelist_cache zlcache; // optional ...
+#endif
};
#ifdef CONFIG_ARCH_POPULATES_NODE_MAP
return 1;
}
+#ifdef CONFIG_NUMA
+/*
+ * zlc_setup - Setup for "zonelist cache". Uses cached zone data to
+ * skip over zones that are not allowed by the cpuset, or that have
+ * been recently (in last second) found to be nearly full. See further
+ * comments in mmzone.h. Reduces cache footprint of zonelist scans
+ * that have to skip over alot of full or unallowed zones.
+ *
+ * If the zonelist cache is present in the passed in zonelist, then
+ * returns a pointer to the allowed node mask (either the current
+ * tasks mems_allowed, or node_online_map.)
+ *
+ * If the zonelist cache is not available for this zonelist, does
+ * nothing and returns NULL.
+ *
+ * If the fullzones BITMAP in the zonelist cache is stale (more than
+ * a second since last zap'd) then we zap it out (clear its bits.)
+ *
+ * We hold off even calling zlc_setup, until after we've checked the
+ * first zone in the zonelist, on the theory that most allocations will
+ * be satisfied from that first zone, so best to examine that zone as
+ * quickly as we can.
+ */
+static nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
+{
+ struct zonelist_cache *zlc; /* cached zonelist speedup info */
+ nodemask_t *allowednodes; /* zonelist_cache approximation */
+
+ zlc = zonelist->zlcache_ptr;
+ if (!zlc)
+ return NULL;
+
+ if (jiffies - zlc->last_full_zap > 1 * HZ) {
+ bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
+ zlc->last_full_zap = jiffies;
+ }
+
+ allowednodes = !in_interrupt() && (alloc_flags & ALLOC_CPUSET) ?
+ &cpuset_current_mems_allowed :
+ &node_online_map;
+ return allowednodes;
+}
+
+/*
+ * Given 'z' scanning a zonelist, run a couple of quick checks to see
+ * if it is worth looking at further for free memory:
+ * 1) Check that the zone isn't thought to be full (doesn't have its
+ * bit set in the zonelist_cache fullzones BITMAP).
+ * 2) Check that the zones node (obtained from the zonelist_cache
+ * z_to_n[] mapping) is allowed in the passed in allowednodes mask.
+ * Return true (non-zero) if zone is worth looking at further, or
+ * else return false (zero) if it is not.
+ *
+ * This check -ignores- the distinction between various watermarks,
+ * such as GFP_HIGH, GFP_ATOMIC, PF_MEMALLOC, ... If a zone is
+ * found to be full for any variation of these watermarks, it will
+ * be considered full for up to one second by all requests, unless
+ * we are so low on memory on all allowed nodes that we are forced
+ * into the second scan of the zonelist.
+ *
+ * In the second scan we ignore this zonelist cache and exactly
+ * apply the watermarks to all zones, even it is slower to do so.
+ * We are low on memory in the second scan, and should leave no stone
+ * unturned looking for a free page.
+ */
+static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zone **z,
+ nodemask_t *allowednodes)
+{
+ struct zonelist_cache *zlc; /* cached zonelist speedup info */
+ int i; /* index of *z in zonelist zones */
+ int n; /* node that zone *z is on */
+
+ zlc = zonelist->zlcache_ptr;
+ if (!zlc)
+ return 1;
+
+ i = z - zonelist->zones;
+ n = zlc->z_to_n[i];
+
+ /* This zone is worth trying if it is allowed but not full */
+ return node_isset(n, *allowednodes) && !test_bit(i, zlc->fullzones);
+}
+
+/*
+ * Given 'z' scanning a zonelist, set the corresponding bit in
+ * zlc->fullzones, so that subsequent attempts to allocate a page
+ * from that zone don't waste time re-examining it.
+ */
+static void zlc_mark_zone_full(struct zonelist *zonelist, struct zone **z)
+{
+ struct zonelist_cache *zlc; /* cached zonelist speedup info */
+ int i; /* index of *z in zonelist zones */
+
+ zlc = zonelist->zlcache_ptr;
+ if (!zlc)
+ return;
+
+ i = z - zonelist->zones;
+
+ set_bit(i, zlc->fullzones);
+}
+
+#else /* CONFIG_NUMA */
+
+static nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
+{
+ return NULL;
+}
+
+static int zlc_zone_worth_trying(struct zonelist *zonelist, struct zone **z,
+ nodemask_t *allowednodes)
+{
+ return 1;
+}
+
+static void zlc_mark_zone_full(struct zonelist *zonelist, struct zone **z)
+{
+}
+#endif /* CONFIG_NUMA */
+
/*
* get_page_from_freelist goes through the zonelist trying to allocate
* a page.
get_page_from_freelist(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, int alloc_flags)
{
- struct zone **z = zonelist->zones;
+ struct zone **z;
struct page *page = NULL;
- int classzone_idx = zone_idx(*z);
+ int classzone_idx = zone_idx(zonelist->zones[0]);
struct zone *zone;
+ nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
+ int zlc_active = 0; /* set if using zonelist_cache */
+ int did_zlc_setup = 0; /* just call zlc_setup() one time */
+zonelist_scan:
/*
- * Go through the zonelist once, looking for a zone with enough free.
+ * Scan zonelist, looking for a zone with enough free.
* See also cpuset_zone_allowed() comment in kernel/cpuset.c.
*/
+ z = zonelist->zones;
+
do {
+ if (NUMA_BUILD && zlc_active &&
+ !zlc_zone_worth_trying(zonelist, z, allowednodes))
+ continue;
zone = *z;
if (unlikely(NUMA_BUILD && (gfp_mask & __GFP_THISNODE) &&
zone->zone_pgdat != zonelist->zones[0]->zone_pgdat))
break;
if ((alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed(zone, gfp_mask))
- continue;
+ goto try_next_zone;
if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
unsigned long mark;
classzone_idx, alloc_flags)) {
if (!zone_reclaim_mode ||
!zone_reclaim(zone, gfp_mask, order))
- continue;
+ goto this_zone_full;
}
}
page = buffered_rmqueue(zonelist, zone, order, gfp_mask);
if (page)
break;
-
+this_zone_full:
+ if (NUMA_BUILD)
+ zlc_mark_zone_full(zonelist, z);
+try_next_zone:
+ if (NUMA_BUILD && !did_zlc_setup) {
+ /* we do zlc_setup after the first zone is tried */
+ allowednodes = zlc_setup(zonelist, alloc_flags);
+ zlc_active = 1;
+ did_zlc_setup = 1;
+ }
} while (*(++z) != NULL);
+
+ if (unlikely(NUMA_BUILD && page == NULL && zlc_active)) {
+ /* Disable zlc cache for second zonelist scan */
+ zlc_active = 0;
+ goto zonelist_scan;
+ }
return page;
}
}
}
+/* Construct the zonelist performance cache - see further mmzone.h */
+static void __meminit build_zonelist_cache(pg_data_t *pgdat)
+{
+ int i;
+
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ struct zonelist *zonelist;
+ struct zonelist_cache *zlc;
+ struct zone **z;
+
+ zonelist = pgdat->node_zonelists + i;
+ zonelist->zlcache_ptr = zlc = &zonelist->zlcache;
+ bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
+ for (z = zonelist->zones; *z; z++)
+ zlc->z_to_n[z - zonelist->zones] = zone_to_nid(*z);
+ }
+}
+
#else /* CONFIG_NUMA */
static void __meminit build_zonelists(pg_data_t *pgdat)
}
}
+/* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
+static void __meminit build_zonelist_cache(pg_data_t *pgdat)
+{
+ int i;
+
+ for (i = 0; i < MAX_NR_ZONES; i++)
+ pgdat->node_zonelists[i].zlcache_ptr = NULL;
+}
+
#endif /* CONFIG_NUMA */
/* return values int ....just for stop_machine_run() */
static int __meminit __build_all_zonelists(void *dummy)
{
int nid;
- for_each_online_node(nid)
+
+ for_each_online_node(nid) {
build_zonelists(NODE_DATA(nid));
+ build_zonelist_cache(NODE_DATA(nid));
+ }
return 0;
}
projects / linux-2.6 / commitdiff