linux-kernel - Re: [RFC 2/5] mm, page_alloc: calculate pageset high and batch once per zone

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Date:   Thu, 10 Sep 2020 12:56:45 +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 2/5] mm, page_alloc: calculate pageset high and batch once
 per zone

On 07.09.20 18:36, Vlastimil Babka wrote:
> We currently call pageset_set_high_and_batch() for each possible cpu,
> which repeats the same calculations of high and batch values.
> 
> Instead call it once per zone, and it applies the calculated values
> to all per-cpu pagesets of the zone.
> 
> This also allows removing zone_pageset_init() and __zone_pcp_update() wrappers.
> 
> No functional change.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/page_alloc.c | 40 +++++++++++++++++-----------------------
>  1 file changed, 17 insertions(+), 23 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0b516208afda..f669a251f654 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6236,12 +6236,13 @@ static void setup_pageset(struct per_cpu_pageset *p)
>  	pageset_update(&p->pcp, 0, 1);
>  }
>  
> -static void pageset_set_high_and_batch(struct zone *zone,
> -				       struct per_cpu_pageset *p)
> +static void zone_set_pageset_high_and_batch(struct zone *zone)
>  {
>  	unsigned long new_high;
>  	unsigned long new_batch;
>  	int fraction = READ_ONCE(percpu_pagelist_fraction);
> +	int cpu;
> +	struct per_cpu_pageset *p;

I would use reverse Christmas tree layout. (same applies to patch #1,
you could put both unsigned long variables into a single line)

[...]

LGTM

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

-- 
Thanks,

David / dhildenb