On Tue 22-09-20 16:37:04, Vlastimil Babka wrote:
> The updates to pcplists' high and batch valued are handled by multiple
> functions that make the calculations hard to follow. Consolidate everything
> to pageset_set_high_and_batch() and remove pageset_set_batch() and
> pageset_set_high() wrappers.
>
> The only special case using one of the removed wrappers was:
> build_all_zonelists_init()
> setup_pageset()
> pageset_set_batch()
> which was hardcoding batch as 0, so we can just open-code a call to
> pageset_update() with constant parameters instead.
>
> No functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
yes this looks better, the original code was really hard to follow.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/page_alloc.c | 49 ++++++++++++++++++++-----------------------------
> 1 file changed, 20 insertions(+), 29 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 60a0e94645a6..a163c5e561f2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5823,7 +5823,7 @@ static void build_zonelists(pg_data_t *pgdat)
> * not check if the processor is online before following the pageset pointer.
> * Other parts of the kernel may not check if the zone is available.
> */
> -static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
> +static void setup_pageset(struct per_cpu_pageset *p);
> static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
> static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
>
> @@ -5891,7 +5891,7 @@ build_all_zonelists_init(void)
> * (a chicken-egg dilemma).
> */
> for_each_possible_cpu(cpu)
> - setup_pageset(&per_cpu(boot_pageset, cpu), 0);
> + setup_pageset(&per_cpu(boot_pageset, cpu));
>
> mminit_verify_zonelist();
> cpuset_init_current_mems_allowed();
> @@ -6200,12 +6200,6 @@ static void pageset_update(struct per_cpu_pages *pcp, unsigned long high,
> pcp->batch = batch;
> }
>
> -/* a companion to pageset_set_high() */
> -static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
> -{
> - pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch));
> -}
> -
> static void pageset_init(struct per_cpu_pageset *p)
> {
> struct per_cpu_pages *pcp;
> @@ -6218,35 +6212,32 @@ static void pageset_init(struct per_cpu_pageset *p)
> INIT_LIST_HEAD(&pcp->lists[migratetype]);
> }
>
> -static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
> +static void setup_pageset(struct per_cpu_pageset *p)
> {
> pageset_init(p);
> - pageset_set_batch(p, batch);
> + pageset_update(&p->pcp, 0, 1);
> }
>
> /*
> - * pageset_set_high() sets the high water mark for hot per_cpu_pagelist
> - * to the value high for the pageset p.
> + * Calculate and set new high and batch values for given per-cpu pageset of a
> + * zone, based on the zone's size and the percpu_pagelist_fraction sysctl.
> */
> -static void pageset_set_high(struct per_cpu_pageset *p,
> - unsigned long high)
> -{
> - unsigned long batch = max(1UL, high / 4);
> - if ((high / 4) > (PAGE_SHIFT * 8))
> - batch = PAGE_SHIFT * 8;
> -
> - pageset_update(&p->pcp, high, batch);
> -}
> -
> static void pageset_set_high_and_batch(struct zone *zone,
> - struct per_cpu_pageset *pcp)
> + struct per_cpu_pageset *p)
> {
> - if (percpu_pagelist_fraction)
> - pageset_set_high(pcp,
> - (zone_managed_pages(zone) /
> - percpu_pagelist_fraction));
> - else
> - pageset_set_batch(pcp, zone_batchsize(zone));
> + unsigned long new_high, new_batch;
> +
> + if (percpu_pagelist_fraction) {
> + new_high = zone_managed_pages(zone) / percpu_pagelist_fraction;
> + new_batch = max(1UL, new_high / 4);
> + if ((new_high / 4) > (PAGE_SHIFT * 8))
> + new_batch = PAGE_SHIFT * 8;
> + } else {
> + new_batch = zone_batchsize(zone);
> + new_high = 6 * new_batch;
> + new_batch = max(1UL, 1 * new_batch);
> + }
> + pageset_update(&p->pcp, new_high, new_batch);
> }
>
> static void __meminit zone_pageset_init(struct zone *zone, int cpu)
> --
> 2.28.0
--
Michal Hocko
SUSE Labs
