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Date: Mon, 8 Jun 2015 14:56:26 +0100
From: Mel Gorman <mgorman@...e.de>
To: Linux-MM <linux-mm@...ck.org>
Cc: Rik van Riel <riel@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 20/25] mm, page_alloc: Remove fair zone allocation policy
The fair zone allocation policy interleaves allocation requests between
zones to avoid an age inversion problem whereby new pages are reclaimed
to balance a zone. Reclaim is now node-based so this should no longer be
an issue and the fair zone allocation policy is not free. This patch
removes it.
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
include/linux/mmzone.h | 2 --
mm/internal.h | 1 -
mm/page_alloc.c | 69 +-------------------------------------------------
mm/vmstat.c | 1 -
4 files changed, 1 insertion(+), 72 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 34050b012409..c551f70951fa 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -114,7 +114,6 @@ struct zone_padding {
enum zone_stat_item {
/* First 128 byte cacheline (assuming 64 bit words) */
NR_FREE_PAGES,
- NR_ALLOC_BATCH,
NR_MLOCK, /* mlock()ed pages found and moved off LRU */
NR_SLAB_RECLAIMABLE,
NR_SLAB_UNRECLAIMABLE,
@@ -521,7 +520,6 @@ struct zone {
enum zone_flags {
ZONE_RECLAIM_LOCKED, /* prevents concurrent reclaim */
ZONE_OOM_LOCKED, /* zone is in OOM killer zonelist */
- ZONE_FAIR_DEPLETED, /* fair zone policy batch depleted */
};
enum pgdat_flags {
diff --git a/mm/internal.h b/mm/internal.h
index 2e4cee6a8739..a24c4a50c33f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -429,6 +429,5 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
#define ALLOC_HIGH 0x20 /* __GFP_HIGH set */
#define ALLOC_CPUSET 0x40 /* check for correct cpuset */
#define ALLOC_CMA 0x80 /* allow allocations from CMA areas */
-#define ALLOC_FAIR 0x100 /* fair zone allocation */
#endif /* __MM_INTERNAL_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ca5da938972..6b3a78420a5e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1698,11 +1698,6 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
get_freepage_migratetype(page));
}
- __mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
- if (atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]) <= 0 &&
- !test_bit(ZONE_FAIR_DEPLETED, &zone->flags))
- set_bit(ZONE_FAIR_DEPLETED, &zone->flags);
-
__count_zone_vm_events(PGALLOC, zone, 1 << order);
zone_statistics(preferred_zone, zone, gfp_flags);
local_irq_restore(flags);
@@ -1967,11 +1962,6 @@ static void zlc_clear_zones_full(struct zonelist *zonelist)
bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
}
-static bool zone_local(struct zone *local_zone, struct zone *zone)
-{
- return local_zone->node == zone->node;
-}
-
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <
@@ -1999,11 +1989,6 @@ static void zlc_clear_zones_full(struct zonelist *zonelist)
{
}
-static bool zone_local(struct zone *local_zone, struct zone *zone)
-{
- return true;
-}
-
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
return true;
@@ -2011,18 +1996,6 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
#endif /* CONFIG_NUMA */
-static void reset_alloc_batches(struct zone *preferred_zone)
-{
- struct zone *zone = preferred_zone->zone_pgdat->node_zones;
-
- do {
- mod_zone_page_state(zone, NR_ALLOC_BATCH,
- high_wmark_pages(zone) - low_wmark_pages(zone) -
- atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
- clear_bit(ZONE_FAIR_DEPLETED, &zone->flags);
- } while (zone++ != preferred_zone);
-}
-
/*
* get_page_from_freelist goes through the zonelist trying to allocate
* a page.
@@ -2040,7 +2013,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
int did_zlc_setup = 0; /* just call zlc_setup() one time */
bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
(gfp_mask & __GFP_WRITE);
- int nr_fair_skipped = 0;
bool zonelist_rescan;
struct pglist_data *last_pgdat = NULL;
@@ -2063,20 +2035,6 @@ zonelist_scan:
!cpuset_zone_allowed(zone, gfp_mask))
continue;
/*
- * Distribute pages in proportion to the individual
- * zone size to ensure fair page aging. The zone a
- * page was allocated in should have no effect on the
- * time the page has in memory before being reclaimed.
- */
- if (alloc_flags & ALLOC_FAIR) {
- if (!zone_local(ac->preferred_zone, zone))
- break;
- if (test_bit(ZONE_FAIR_DEPLETED, &zone->flags)) {
- nr_fair_skipped++;
- continue;
- }
- }
- /*
* When allocating a page cache page for writing, we
* want to get it from a zone that is within its dirty
* limit, such that no single zone holds more than its
@@ -2186,24 +2144,6 @@ this_zone_full:
zlc_mark_zone_full(zonelist, z);
}
- /*
- * The first pass makes sure allocations are spread fairly within the
- * local node. However, the local node might have free pages left
- * after the fairness batches are exhausted, and remote zones haven't
- * even been considered yet. Try once more without fairness, and
- * include remote zones now, before entering the slowpath and waking
- * kswapd: prefer spilling to a remote zone over swapping locally.
- */
- if (alloc_flags & ALLOC_FAIR) {
- alloc_flags &= ~ALLOC_FAIR;
- if (nr_fair_skipped) {
- zonelist_rescan = true;
- reset_alloc_batches(ac->preferred_zone);
- }
- if (nr_online_nodes > 1)
- zonelist_rescan = true;
- }
-
if (unlikely(IS_ENABLED(CONFIG_NUMA) && zlc_active)) {
/* Disable zlc cache for second zonelist scan */
zlc_active = 0;
@@ -2808,7 +2748,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
struct zoneref *preferred_zoneref;
struct page *page = NULL;
unsigned int cpuset_mems_cookie;
- int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR;
+ int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET;
gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
struct alloc_context ac = {
.high_zoneidx = gfp_zone(gfp_mask),
@@ -4950,9 +4890,6 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
zone_seqlock_init(zone);
zone_pcp_init(zone);
- /* For bootup, initialized properly in watermark setup */
- mod_zone_page_state(zone, NR_ALLOC_BATCH, zone->managed_pages);
-
if (!size)
continue;
@@ -5751,10 +5688,6 @@ static void __setup_per_zone_wmarks(void)
zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + (tmp >> 2);
zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1);
- __mod_zone_page_state(zone, NR_ALLOC_BATCH,
- high_wmark_pages(zone) - low_wmark_pages(zone) -
- atomic_long_read(&zone->vm_stat[NR_ALLOC_BATCH]));
-
setup_zone_migrate_reserve(zone);
spin_unlock_irqrestore(&zone->lock, flags);
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index d805df47d3ae..c3fdd88961ff 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -893,7 +893,6 @@ int fragmentation_index(struct zone *zone, unsigned int order)
const char * const vmstat_text[] = {
/* enum zone_stat_item countes */
"nr_free_pages",
- "nr_alloc_batch",
"nr_mlock",
"nr_slab_reclaimable",
"nr_slab_unreclaimable",
--
2.3.5
--
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