The zonelist cache (zlc) was introduced to quickly skip over full zones
when zone_reclaim was active. This made some sense before there were zone
flags and when zone_reclaim was the default. Now reclaim is node-based and
zone_reclaim is disabled by default. If it was being implemented today,
it would use a pgdat flag with a timeout to reset it but as zone_reclaim
is extraordinarily expensive the entire concept is of dubious merit. This
patch deletes it entirely.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
include/linux/mmzone.h | 78 +-----------------
mm/page_alloc.c | 210 +------------------------------------------------
mm/vmstat.c | 8 +-
3 files changed, 8 insertions(+), 288 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 84fcb7aafb2b..89a88ba096f3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -558,84 +558,14 @@ static inline bool zone_is_empty(struct zone *zone)
#define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
#ifdef CONFIG_NUMA
-
/*
* The NUMA zonelists are doubled because we need zonelists that restrict the
* allocations to a single node for __GFP_THISNODE.
*
- * [0] : Zonelist with fallback
- * [1] : No fallback (__GFP_THISNODE)
+ * [0] : Zonelist with fallback
+ * [1] : No fallback (__GFP_THISNODE)
*/
#define MAX_ZONELISTS 2
-
-
-/*
- * 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 {
- unsigned short z_to_n[MAX_ZONES_PER_ZONELIST]; /* zone->nid */
- DECLARE_BITMAP(fullzones, MAX_ZONES_PER_ZONELIST); /* zone full? */
- unsigned long last_full_zap; /* when last zap'd (jiffies) */
-};
-#else
-#define MAX_ZONELISTS 1
-struct zonelist_cache;
#endif
/*
@@ -665,11 +595,7 @@ struct zoneref {
* zonelist_node_idx() - Return the index of the node for an entry
*/
struct zonelist {
- struct zonelist_cache *zlcache_ptr; // NULL or &zlcache
struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
-#ifdef CONFIG_NUMA
- struct zonelist_cache zlcache; // optional ...
-#endif
};
#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 47e6332d7566..4108743eb801 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1846,154 +1846,16 @@ bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
}
#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 a lot of full or unallowed zones.
- *
- * If the zonelist cache is present in the passed zonelist, then
- * returns a pointer to the allowed node mask (either the current
- * tasks mems_allowed, or node_states[N_MEMORY].)
- *
- * 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 (time_after(jiffies, zlc->last_full_zap + 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_states[N_MEMORY];
- 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 zoneref *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->_zonerefs;
- 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 zoneref *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->_zonerefs;
-
- set_bit(i, zlc->fullzones);
-}
-
-/*
- * clear all zones full, called after direct reclaim makes progress so that
- * a zone that was recently full is not skipped over for up to a second
- */
-static void zlc_clear_zones_full(struct zonelist *zonelist)
-{
- struct zonelist_cache *zlc; /* cached zonelist speedup info */
-
- zlc = zonelist->zlcache_ptr;
- if (!zlc)
- return;
-
- bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
-}
-
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <
RECLAIM_DISTANCE;
}
-
#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 zoneref *z,
- nodemask_t *allowednodes)
-{
- return 1;
-}
-
-static void zlc_mark_zone_full(struct zonelist *zonelist, struct zoneref *z)
-{
-}
-
-static void zlc_clear_zones_full(struct zonelist *zonelist)
-{
-}
-
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
return true;
}
-
#endif /* CONFIG_NUMA */
/*
@@ -2008,17 +1870,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
struct zoneref *z;
struct page *page = NULL;
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 */
bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
(gfp_mask & __GFP_WRITE);
- bool zonelist_rescan;
struct pglist_data *last_pgdat = NULL;
-zonelist_scan:
- zonelist_rescan = false;
-
/*
* Scan zonelist, looking for a zone with enough free.
* See also __cpuset_node_allowed() comment in kernel/cpuset.c.
@@ -2027,9 +1882,6 @@ zonelist_scan:
ac->nodemask) {
unsigned long mark;
- if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
- !zlc_zone_worth_trying(zonelist, z, allowednodes))
- continue;
if (cpusets_enabled() &&
(alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed(zone, gfp_mask))
@@ -2079,26 +1931,6 @@ zonelist_scan:
!zone_allows_reclaim(ac->preferred_zone, zone))
goto this_zone_full;
- if (IS_ENABLED(CONFIG_NUMA) &&
- !did_zlc_setup && nr_online_nodes > 1) {
- /*
- * we do zlc_setup if there are multiple nodes
- * and before considering the first zone allowed
- * by the cpuset.
- */
- allowednodes = zlc_setup(zonelist, alloc_flags);
- zlc_active = 1;
- did_zlc_setup = 1;
- }
-
- /*
- * As we may have just activated ZLC, check if the first
- * eligible zone has failed node_reclaim recently.
- */
- if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
- !zlc_zone_worth_trying(zonelist, z, allowednodes))
- continue;
-
/* Skip if we have already attemped node_reclaim */
if (last_pgdat == zone->zone_pgdat)
goto try_this_zone;
@@ -2145,19 +1977,8 @@ try_this_zone:
}
this_zone_full:
last_pgdat = zone->zone_pgdat;
- if (IS_ENABLED(CONFIG_NUMA) && zlc_active)
- zlc_mark_zone_full(zonelist, z);
}
- if (unlikely(IS_ENABLED(CONFIG_NUMA) && zlc_active)) {
- /* Disable zlc cache for second zonelist scan */
- zlc_active = 0;
- zonelist_rescan = true;
- }
-
- if (zonelist_rescan)
- goto zonelist_scan;
-
return NULL;
}
@@ -2440,10 +2261,6 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
if (unlikely(!(*did_some_progress)))
return NULL;
- /* After successful reclaim, reconsider all zones for allocation */
- if (IS_ENABLED(CONFIG_NUMA))
- zlc_clear_zones_full(ac->zonelist);
-
retry:
page = get_page_from_freelist(gfp_mask, order,
alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
@@ -2757,7 +2574,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
struct alloc_context ac = {
.high_zoneidx = gfp_zone(gfp_mask),
- .nodemask = nodemask,
+ .nodemask = nodemask ? : &cpuset_current_mems_allowed,
.migratetype = gfpflags_to_migratetype(gfp_mask),
};
@@ -2788,8 +2605,7 @@ retry_cpuset:
ac.zonelist = zonelist;
/* The preferred zone is used for statistics later */
preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx,
- ac.nodemask ? : &cpuset_current_mems_allowed,
- &ac.preferred_zone);
+ ac.nodemask, &ac.preferred_zone);
if (!ac.preferred_zone)
goto out;
ac.classzone_idx = zonelist_zone_idx(preferred_zoneref);
@@ -3674,20 +3490,6 @@ static void build_zonelists(pg_data_t *pgdat)
build_thisnode_zonelists(pgdat);
}
-/* Construct the zonelist performance cache - see further mmzone.h */
-static void build_zonelist_cache(pg_data_t *pgdat)
-{
- struct zonelist *zonelist;
- struct zonelist_cache *zlc;
- struct zoneref *z;
-
- zonelist = &pgdat->node_zonelists[0];
- zonelist->zlcache_ptr = zlc = &zonelist->zlcache;
- bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
- for (z = zonelist->_zonerefs; z->zone; z++)
- zlc->z_to_n[z - zonelist->_zonerefs] = zonelist_node_idx(z);
-}
-
#ifdef CONFIG_HAVE_MEMORYLESS_NODES
/*
* Return node id of node used for "local" allocations.
@@ -3748,12 +3550,6 @@ static void build_zonelists(pg_data_t *pgdat)
zonelist->_zonerefs[j].zone_idx = 0;
}
-/* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
-static void build_zonelist_cache(pg_data_t *pgdat)
-{
- pgdat->node_zonelists[0].zlcache_ptr = NULL;
-}
-
#endif /* CONFIG_NUMA */
/*
@@ -3794,14 +3590,12 @@ static int __build_all_zonelists(void *data)
if (self && !node_online(self->node_id)) {
build_zonelists(self);
- build_zonelist_cache(self);
}
for_each_online_node(nid) {
pg_data_t *pgdat = NODE_DATA(nid);
build_zonelists(pgdat);
- build_zonelist_cache(pgdat);
}
/*
diff --git a/mm/vmstat.c b/mm/vmstat.c
index c3fdd88961ff..30b17cf07197 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1500,14 +1500,14 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
v[i] = global_page_state(i);
v += NR_VM_ZONE_STAT_ITEMS;
- for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
- v[i] = global_node_page_state(i);
- v += NR_VM_NODE_STAT_ITEMS;
-
global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
v + NR_DIRTY_THRESHOLD);
v += NR_VM_WRITEBACK_STAT_ITEMS;
+ for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
+ v[i] = global_node_page_state(i);
+ v += NR_VM_NODE_STAT_ITEMS;
+
#ifdef CONFIG_VM_EVENT_COUNTERS
all_vm_events(v);
v[PGPGIN] /= 2; /* sectors -> kbytes */
--
2.3.5
--
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