linux-kernel - Re: [PATCH 1/3] mm, pcp: Share common code between memory hotplug and percpu sysctl handler

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Message-ID: <20191018125119.GO5017@dhcp22.suse.cz>
Date:   Fri, 18 Oct 2019 14:51:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Borislav Petkov <bp@...en8.de>, Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm, pcp: Share common code between memory hotplug
 and percpu sysctl handler

On Fri 18-10-19 11:56:04, Mel Gorman wrote:
> Both the percpu_pagelist_fraction sysctl handler and memory hotplug
> have a common requirement of updating the pcpu page allocation batch
> and high values. Split the relevant helper to share common code.
> 
> No functional change.
> 
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/page_alloc.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c0b2e0306720..cafe568d36f6 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7983,6 +7983,15 @@ int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write,
>  	return 0;
>  }
>  
> +static void __zone_pcp_update(struct zone *zone)
> +{
> +	unsigned int cpu;
> +
> +	for_each_possible_cpu(cpu)
> +		pageset_set_high_and_batch(zone,
> +				per_cpu_ptr(zone->pageset, cpu));
> +}
> +
>  /*
>   * percpu_pagelist_fraction - changes the pcp->high for each zone on each
>   * cpu.  It is the fraction of total pages in each zone that a hot per cpu
> @@ -8014,13 +8023,8 @@ int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *table, int write,
>  	if (percpu_pagelist_fraction == old_percpu_pagelist_fraction)
>  		goto out;
>  
> -	for_each_populated_zone(zone) {
> -		unsigned int cpu;
> -
> -		for_each_possible_cpu(cpu)
> -			pageset_set_high_and_batch(zone,
> -					per_cpu_ptr(zone->pageset, cpu));
> -	}
> +	for_each_populated_zone(zone)
> +		__zone_pcp_update(zone);
>  out:
>  	mutex_unlock(&pcp_batch_high_lock);
>  	return ret;
> @@ -8519,11 +8523,8 @@ void free_contig_range(unsigned long pfn, unsigned int nr_pages)
>   */
>  void __meminit zone_pcp_update(struct zone *zone)
>  {
> -	unsigned cpu;
>  	mutex_lock(&pcp_batch_high_lock);
> -	for_each_possible_cpu(cpu)
> -		pageset_set_high_and_batch(zone,
> -				per_cpu_ptr(zone->pageset, cpu));
> +	__zone_pcp_update(zone);
>  	mutex_unlock(&pcp_batch_high_lock);
>  }
>  #endif
> -- 
> 2.16.4
> 

-- 
Michal Hocko
SUSE Labs