On Thu 08-10-20 13:41:57, Vlastimil Babka wrote:
> We initialize boot-time pagesets with setup_pageset(), which sets high and
> batch values that effectively disable pcplists.
>
> We can remove this wrapper if we just set these values for all pagesets in
> pageset_init(). Non-boot pagesets then subsequently update them to the proper
> values.
>
> No functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Btw. where do we initialize pcp->count? I thought that pcp allocator
zeroes out the allocated memory but alloc_percpu is GFP_KERNEL like.
> ---
> mm/page_alloc.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 463f40b12aca..f827b42a2475 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5899,7 +5899,7 @@ 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);
> +static void pageset_init(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);
>
> @@ -5967,7 +5967,7 @@ build_all_zonelists_init(void)
> * (a chicken-egg dilemma).
> */
> for_each_possible_cpu(cpu)
> - setup_pageset(&per_cpu(boot_pageset, cpu));
> + pageset_init(&per_cpu(boot_pageset, cpu));
>
> mminit_verify_zonelist();
> cpuset_init_current_mems_allowed();
> @@ -6286,12 +6286,15 @@ static void pageset_init(struct per_cpu_pageset *p)
> pcp = &p->pcp;
> for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
> INIT_LIST_HEAD(&pcp->lists[migratetype]);
> -}
>
> -static void setup_pageset(struct per_cpu_pageset *p)
> -{
> - pageset_init(p);
> - pageset_update(&p->pcp, 0, 1);
> + /*
> + * Set batch and high values safe for a boot pageset. A true percpu
> + * pageset's initialization will update them subsequently. Here we don't
> + * need to be as careful as pageset_update() as nobody can access the
> + * pageset yet.
> + */
> + pcp->high = 0;
> + pcp->batch = 1;
> }
>
> /*
> --
> 2.28.0
--
Michal Hocko
SUSE Labs
