Re: [PATCH 3/9] mm, page_alloc: remove setup_pageset()

David Hildenbrand
2020-09-25T10:19:35Z

On 22.09.20 16:37, 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@suse.cz>
> ---
> 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 26069c8d1b19..76c2b4578723 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);
> +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);
>
> @@ -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));
> + pageset_init(&per_cpu(boot_pageset, cpu));
>
> mminit_verify_zonelist();
> cpuset_init_current_mems_allowed();
> @@ -6210,12 +6210,15 @@ 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;
> }
>
> /*
>

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb