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Subject[PATCH 29/35] Do not store the PCP high and batch watermarks in the per-cpu structure
Date
Currently, there are high and batch counters in the per-cpu structure.
This might have made sense when there was hot and cold per-cpu
structures but that is no longer the case. In practice, all the per-cpu
structures for a zone contain the same values and they are read-mostly.
This patch stores them in the zone with the watermarks which are also
read-mostly.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
include/linux/mmzone.h | 8 ++++++--
mm/page_alloc.c | 43 +++++++++++++++++++++++--------------------
mm/vmstat.c | 4 ++--
3 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index eed6867..b4fba09 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -166,8 +166,6 @@ static inline int is_unevictable_lru(enum lru_list l)

struct per_cpu_pages {
int count; /* number of pages in the list */
- int high; /* high watermark, emptying needed */
- int batch; /* chunk size for buddy add/remove */

/* Lists of pages, one per migrate type stored on the pcp-lists */
struct list_head lists[MIGRATE_PCPTYPES];
@@ -285,6 +283,12 @@ struct zone {
unsigned long pages_mark[3];
};

+ /* high watermark for per-cpu lists, emptying needed */
+ u16 pcp_high;
+
+ /* chunk size for buddy add/remove to per-cpu lists*/
+ u16 pcp_batch;
+
/*
* We don't know if the memory that we're going to allocate will be freeable
* or/and it will be released eventually, so to avoid totally wasting several
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index edadab1..77e9970 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -975,8 +975,8 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
int to_drain;

local_irq_save(flags);
- if (pcp->count >= pcp->batch)
- to_drain = pcp->batch;
+ if (pcp->count >= zone->pcp_batch)
+ to_drain = zone->pcp_batch;
else
to_drain = pcp->count;
free_pcppages_bulk(zone, to_drain, pcp, 0);
@@ -1119,8 +1119,8 @@ static void free_hot_cold_page(struct page *page, int order, int cold)
set_page_private(page, migratetype);
page->index = order;
add_pcp_page(pcp, page, cold);
- if (pcp->count >= pcp->high)
- free_pcppages_bulk(zone, pcp->batch, pcp, migratetype);
+ if (pcp->count >= zone->pcp_high)
+ free_pcppages_bulk(zone, zone->pcp_batch, pcp, migratetype);

out:
local_irq_restore(flags);
@@ -1184,7 +1184,7 @@ again:

pcp = &zone_pcp(zone, cpu)->pcp;
list = &pcp->lists[migratetype];
- batch = max(1, pcp->batch >> order);
+ batch = max(1, zone->pcp_batch >> order);
local_irq_save(flags);
if (list_empty(list)) {
delta = rmqueue_bulk(zone, order, batch,
@@ -2144,8 +2144,8 @@ void show_free_areas(void)
pageset = zone_pcp(zone, cpu);

printk("CPU %4d: hi:%5d, btch:%4d usd:%4d\n",
- cpu, pageset->pcp.high,
- pageset->pcp.batch, pageset->pcp.count);
+ cpu, zone->pcp_high,
+ zone->pcp_batch, pageset->pcp.count);
}
}

@@ -2975,7 +2975,8 @@ static int zone_batchsize(struct zone *zone)
return batch;
}

-static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
+static void setup_pageset(struct zone *zone,
+ struct per_cpu_pageset *p, unsigned long batch)
{
struct per_cpu_pages *pcp;
int migratetype;
@@ -2984,8 +2985,8 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)

pcp = &p->pcp;
pcp->count = 0;
- pcp->high = 6 * batch;
- pcp->batch = max(1UL, 1 * batch);
+ zone->pcp_high = 6 * batch;
+ zone->pcp_batch = max(1UL, 1 * batch);
for (migratetype = 0; migratetype < MIGRATE_TYPES; migratetype++)
INIT_LIST_HEAD(&pcp->lists[migratetype]);
}
@@ -2995,16 +2996,17 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
* to the value high for the pageset p.
*/

-static void setup_pagelist_highmark(struct per_cpu_pageset *p,
+static void setup_pagelist_highmark(struct zone *zone,
+ struct per_cpu_pageset *p,
unsigned long high)
{
struct per_cpu_pages *pcp;

pcp = &p->pcp;
- pcp->high = high;
- pcp->batch = max(1UL, high/4);
+ zone->pcp_high = high;
+ zone->pcp_batch = max(1UL, high/4);
if ((high/4) > (PAGE_SHIFT * 8))
- pcp->batch = PAGE_SHIFT * 8;
+ zone->pcp_batch = PAGE_SHIFT * 8;
}


@@ -3049,10 +3051,10 @@ static int __cpuinit process_zones(int cpu)
if (!zone_pcp(zone, cpu))
goto bad;

- setup_pageset(zone_pcp(zone, cpu), zone_batchsize(zone));
+ setup_pageset(zone, zone_pcp(zone, cpu), zone_batchsize(zone));

if (percpu_pagelist_fraction)
- setup_pagelist_highmark(zone_pcp(zone, cpu),
+ setup_pagelist_highmark(zone, zone_pcp(zone, cpu),
(zone->present_pages / percpu_pagelist_fraction));
}

@@ -3178,9 +3180,9 @@ static __meminit void zone_pcp_init(struct zone *zone)
#ifdef CONFIG_NUMA
/* Early boot. Slab allocator not functional yet */
zone_pcp(zone, cpu) = &boot_pageset[cpu];
- setup_pageset(&boot_pageset[cpu],0);
+ setup_pageset(zone, &boot_pageset[cpu], 0);
#else
- setup_pageset(zone_pcp(zone,cpu), batch);
+ setup_pageset(zone, zone_pcp(zone, cpu), batch);
#endif
}
if (zone->present_pages)
@@ -4771,7 +4773,7 @@ int lowmem_reserve_ratio_sysctl_handler(ctl_table *table, int write,
}

/*
- * percpu_pagelist_fraction - changes the pcp->high for each zone on each
+ * percpu_pagelist_fraction - changes the zone->pcp_high for each zone on each
* cpu. It is the fraction of total pages in each zone that a hot per cpu pagelist
* can have before it gets flushed back to buddy allocator.
*/
@@ -4790,7 +4792,8 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
for_each_online_cpu(cpu) {
unsigned long high;
high = zone->present_pages / percpu_pagelist_fraction;
- setup_pagelist_highmark(zone_pcp(zone, cpu), high);
+ setup_pagelist_highmark(zone, zone_pcp(zone, cpu),
+ high);
}
}
return 0;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 9114974..3be59b1 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -766,8 +766,8 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
"\n batch: %i",
i,
pageset->pcp.count,
- pageset->pcp.high,
- pageset->pcp.batch);
+ zone->pcp_high,
+ zone->pcp_batch);
#ifdef CONFIG_SMP
seq_printf(m, "\n vm stats threshold: %d",
pageset->stat_threshold);
--
1.5.6.5


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