linux-kernel - Re: [RFC 3/5] mm, page_alloc(): remove setup

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Message-ID: <1c56d989-a0bf-b742-82fe-5b60e7c148b9@redhat.com>
Date:   Thu, 10 Sep 2020 13:00:49 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Oscar Salvador <osalvador@...e.de>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [RFC 3/5] mm, page_alloc(): remove setup_pageset()

On 07.09.20 18:36, 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 specific
> values.
> 

subject: s/page_alloc()/page_alloc/ to make it look consistent

> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/page_alloc.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f669a251f654..a0cab2c6055e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5902,7 +5902,7 @@ 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();
> @@ -6228,12 +6228,13 @@ 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. Proper pageset's
> +	 * initialization will update them.
> +	 */
> +	pcp->high = 0;
> +	pcp->batch  = 1;
>  }
>  
>  static void zone_set_pageset_high_and_batch(struct zone *zone)
> 

Had the same thought about barriers being useless when the pageset is
not hot.

LGTM

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

-- 
Thanks,

David / dhildenb