On 4/14/21 3:39 PM, Mel Gorman wrote:
> Now that the zone_statistics are simple counters that do not require
> special protection, the bulk allocator accounting updates can be batch
> updated without adding too much complexity with protected RMW updates or
> using xchg.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> include/linux/vmstat.h | 8 ++++++++
> mm/page_alloc.c | 30 +++++++++++++-----------------
> 2 files changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index dde4dec4e7dd..8473b8fa9756 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -246,6 +246,14 @@ __count_numa_event(struct zone *zone, enum numa_stat_item item)
> raw_cpu_inc(pzstats->vm_numa_event[item]);
> }
>
> +static inline void
> +__count_numa_events(struct zone *zone, enum numa_stat_item item, long delta)
> +{
> + struct per_cpu_zonestat __percpu *pzstats = zone->per_cpu_zonestats;
> +
> + raw_cpu_add(pzstats->vm_numa_event[item], delta);
> +}
> +
> extern void __count_numa_event(struct zone *zone, enum numa_stat_item item);
> extern unsigned long sum_zone_node_page_state(int node,
> enum zone_stat_item item);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9d0f047647e3..cff0f1c98b28 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3411,7 +3411,8 @@ void __putback_isolated_page(struct page *page, unsigned int order, int mt)
> *
> * Must be called with interrupts disabled.
> */
> -static inline void zone_statistics(struct zone *preferred_zone, struct zone *z)
> +static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
> + long nr_account)
> {
> #ifdef CONFIG_NUMA
> enum numa_stat_item local_stat = NUMA_LOCAL;
> @@ -3424,12 +3425,12 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z)
> local_stat = NUMA_OTHER;
>
> if (zone_to_nid(z) == zone_to_nid(preferred_zone))
> - __count_numa_event(z, NUMA_HIT);
> + __count_numa_events(z, NUMA_HIT, nr_account);
> else {
> - __count_numa_event(z, NUMA_MISS);
> - __count_numa_event(preferred_zone, NUMA_FOREIGN);
> + __count_numa_events(z, NUMA_MISS, nr_account);
> + __count_numa_events(preferred_zone, NUMA_FOREIGN, nr_account);
> }
> - __count_numa_event(z, local_stat);
> + __count_numa_events(z, local_stat, nr_account);
> #endif
> }
>
> @@ -3475,7 +3476,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list);
> if (page) {
> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
> - zone_statistics(preferred_zone, zone);
> + zone_statistics(preferred_zone, zone, 1);
> }
> local_unlock_irqrestore(&pagesets.lock, flags);
> return page;
> @@ -3536,7 +3537,7 @@ struct page *rmqueue(struct zone *preferred_zone,
> get_pcppage_migratetype(page));
>
> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> - zone_statistics(preferred_zone, zone);
> + zone_statistics(preferred_zone, zone, 1);
> local_irq_restore(flags);
>
> out:
> @@ -5019,7 +5020,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> struct alloc_context ac;
> gfp_t alloc_gfp;
> unsigned int alloc_flags = ALLOC_WMARK_LOW;
> - int nr_populated = 0;
> + int nr_populated = 0, nr_account = 0;
>
> if (unlikely(nr_pages <= 0))
> return 0;
> @@ -5092,15 +5093,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> goto failed_irq;
> break;
> }
> -
> - /*
> - * Ideally this would be batched but the best way to do
> - * that cheaply is to first convert zone_statistics to
> - * be inaccurate per-cpu counter like vm_events to avoid
> - * a RMW cycle then do the accounting with IRQs enabled.
> - */
> - __count_zid_vm_events(PGALLOC, zone_idx(zone), 1);
> - zone_statistics(ac.preferred_zoneref->zone, zone);
> + nr_account++;
>
> prep_new_page(page, 0, gfp, 0);
> if (page_list)
> @@ -5110,6 +5103,9 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> nr_populated++;
> }
>
> + __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
> + zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
> +
> local_unlock_irqrestore(&pagesets.lock, flags);
>
> return nr_populated;
>
