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Date: Tue, 18 Aug 2009 13:47:52 +0200
From: Nick Piggin <npiggin@...e.de>
To: Mel Gorman <mel@....ul.ie>
Cc: Linux Memory Management List <linux-mm@...ck.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] page-allocator: Move pcp static fields for high and batch off-pcp and onto the zone
On Tue, Aug 18, 2009 at 12:16:02PM +0100, Mel Gorman wrote:
> 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.
Hmm.. I did have some patches a long long time ago that among other
things made the lists larger for the local node only....
But I guess if something like that is ever shown to be a good idea
then we can go back to the old scheme. So yeah this seems OK.
>
> Signed-off-by: Mel Gorman <mel@....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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