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    Subject[PATCH 3/3] page-allocator: Move pcp static fields for high and batch off-pcp and onto the zone
    Date
    Having multiple lists per PCPU increased the size of the per-pcpu
    structure. Two of the fields, high and batch, do not change within a
    zone making that information redundant. This patch moves those fields
    off the PCP and onto the zone to reduce the size of the PCPU.

    Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    ---
    include/linux/mmzone.h | 9 +++++----
    mm/page_alloc.c | 47 +++++++++++++++++++++++++----------------------
    mm/vmstat.c | 4 ++--
    3 files changed, 32 insertions(+), 28 deletions(-)

    diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
    index 6e0b624..57a3ef0 100644
    --- a/include/linux/mmzone.h
    +++ b/include/linux/mmzone.h
    @@ -167,12 +167,10 @@ enum zone_watermarks {
    #define high_wmark_pages(z) (z->watermark[WMARK_HIGH])

    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];
    +
    + int count; /* number of pages in the list */
    };

    struct per_cpu_pageset {
    @@ -284,6 +282,9 @@ struct zone {
    /* zone watermarks, access with *_wmark_pages(zone) macros */
    unsigned long watermark[NR_WMARK];

    + int pcp_high; /* high watermark, emptying needed */
    + int pcp_batch; /* chunk size for buddy add/remove */
    +
    /*
    * 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 dd3f306..65cdfbf 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -988,8 +988,8 @@ 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);
    @@ -1129,9 +1129,9 @@ static void free_hot_cold_page(struct page *page, int cold)
    else
    list_add(&page->lru, &pcp->lists[migratetype]);
    pcp->count++;
    - if (pcp->count >= pcp->high) {
    - free_pcppages_bulk(zone, pcp->batch, pcp);
    - pcp->count -= pcp->batch;
    + if (pcp->count >= zone->pcp_high) {
    + free_pcppages_bulk(zone, zone->pcp_batch, pcp);
    + pcp->count -= zone->pcp_batch;
    }

    out:
    @@ -1199,7 +1199,7 @@ again:
    local_irq_save(flags);
    if (list_empty(list)) {
    pcp->count += rmqueue_bulk(zone, 0,
    - pcp->batch, list,
    + zone->pcp_batch, list,
    migratetype, cold);
    if (unlikely(list_empty(list)))
    goto failed;
    @@ -2178,8 +2178,8 @@ 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);
    }
    }

    @@ -3045,7 +3045,9 @@ static int zone_batchsize(struct zone *zone)
    #endif
    }

    -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;
    @@ -3054,8 +3056,8 @@ 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_PCPTYPES; migratetype++)
    INIT_LIST_HEAD(&pcp->lists[migratetype]);
    }
    @@ -3065,16 +3067,17 @@ 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;
    }


    @@ -3115,10 +3118,10 @@ 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));
    }

    @@ -3250,7 +3253,7 @@ static int __zone_pcp_update(void *data)

    local_irq_save(flags);
    free_pcppages_bulk(zone, pcp->count, pcp);
    - setup_pageset(pset, batch);
    + setup_pageset(zone, pset, batch);
    local_irq_restore(flags);
    }
    return 0;
    @@ -3270,9 +3273,9 @@ 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)
    @@ -4781,7 +4784,7 @@ 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.
    */
    @@ -4800,7 +4803,7 @@ 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 c81321f..a9d23c3 100644
    --- a/mm/vmstat.c
    +++ b/mm/vmstat.c
    @@ -746,8 +746,8 @@ 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);
    --
    1.6.3.3


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