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mm, page_alloc: remove fair zone allocation policy

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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.

Link: http://lkml.kernel.org/r/1467970510-21195-30-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
tirimbino
Mel Gorman 9 years ago committed by Linus Torvalds
parent e5146b12e2
commit e6cbd7f2ef
4 changed files with 2 additions and 83 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 5
      include/linux/mmzone.h
  2. 1
      mm/internal.h
  3. 75
      mm/page_alloc.c
  4. 4
      mm/vmstat.c

5
include/linux/mmzone.h
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@ -110,7 +110,6 @@ struct zone_padding {
enum zone_stat_item {
/* First 128 byte cacheline (assuming 64 bit words) */
NR_FREE_PAGES,
NR_ALLOC_BATCH,
NR_ZONE_LRU_BASE, /* Used only for compaction and reclaim retry */
NR_ZONE_LRU_ANON = NR_ZONE_LRU_BASE,
NR_ZONE_LRU_FILE,
@ -516,10 +515,6 @@ struct zone {
atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
} ____cacheline_internodealigned_in_smp;
enum zone_flags {
ZONE_FAIR_DEPLETED, /* fair zone policy batch depleted */
};
enum pgdat_flags {
PGDAT_CONGESTED, /* pgdat has many dirty pages backed by
* a congested BDI

1
mm/internal.h
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@ -467,7 +467,6 @@ 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 */
enum ttu_flags;
struct tlbflush_unmap_batch;

75
mm/page_alloc.c
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@ -2587,7 +2587,6 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
else
page = list_first_entry(list, struct page, lru);
__dec_zone_state(zone, NR_ALLOC_BATCH);
list_del(&page->lru);
pcp->count--;
@ -2613,15 +2612,10 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
spin_unlock(&zone->lock);
if (!page)
goto failed;
__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));
__mod_zone_freepage_state(zone, -(1 << order),
get_pcppage_migratetype(page));
}
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);
@ -2832,40 +2826,18 @@ bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
}
#ifdef CONFIG_NUMA
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)) <
RECLAIM_DISTANCE;
}
#else /* CONFIG_NUMA */
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;
}
#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.
@ -2876,10 +2848,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
{
struct zoneref *z = ac->preferred_zoneref;
struct zone *zone;
bool fair_skipped = false;
bool apply_fair = (alloc_flags & ALLOC_FAIR);
zonelist_scan:
/*
* Scan zonelist, looking for a zone with enough free.
* See also __cpuset_node_allowed() comment in kernel/cpuset.c.
@ -2893,23 +2861,6 @@ zonelist_scan:
(alloc_flags & ALLOC_CPUSET) &&
!__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 (apply_fair) {
if (test_bit(ZONE_FAIR_DEPLETED, &zone->flags)) {
fair_skipped = true;
continue;
}
if (!zone_local(ac->preferred_zoneref->zone, zone)) {
if (fair_skipped)
goto reset_fair;
apply_fair = false;
}
}
/*
* When allocating a page cache page for writing, we
* want to get it from a node that is within its dirty
@ -2981,23 +2932,6 @@ try_this_zone:
}
}
/*
* 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 (fair_skipped) {
reset_fair:
apply_fair = false;
fair_skipped = false;
reset_alloc_batches(ac->preferred_zoneref->zone);
z = ac->preferred_zoneref;
goto zonelist_scan;
}
return NULL;
}
@ -3746,7 +3680,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
{
struct page *page;
unsigned int cpuset_mems_cookie;
unsigned int alloc_flags = ALLOC_WMARK_LOW|ALLOC_FAIR;
unsigned int alloc_flags = ALLOC_WMARK_LOW;
gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */
struct alloc_context ac = {
.high_zoneidx = gfp_zone(gfp_mask),
@ -5958,9 +5892,6 @@ 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;
@ -6808,10 +6739,6 @@ static void __setup_per_zone_wmarks(void)
zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + tmp;
zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;
__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]));
spin_unlock_irqrestore(&zone->lock, flags);
}

4
mm/vmstat.c
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@ -921,7 +921,6 @@ 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_zone_anon_lru",
"nr_zone_file_lru",
"nr_zone_write_pending",
@ -1632,10 +1631,9 @@ int vmstat_refresh(struct ctl_table *table, int write,
val = atomic_long_read(&vm_zone_stat[i]);
if (val < 0) {
switch (i) {
case NR_ALLOC_BATCH:
case NR_PAGES_SCANNED:
/*
* These are often seen to go negative in
* This is often seen to go negative in
* recent kernels, but not to go permanently
* negative. Whilst it would be nicer not to
* have exceptions, rooting them out would be

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