linux-kernel - Re: [PATCH v9 3/8] mm,memory_hotplug: Factor out adjusting present pages into adjust_present_page

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Message-ID: <YH6i09ieDte+xog8@dhcp22.suse.cz>
Date:   Tue, 20 Apr 2021 11:45:55 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 3/8] mm,memory_hotplug: Factor out adjusting present
 pages into adjust_present_page_count()

On Fri 16-04-21 13:24:06, Oscar Salvador wrote:
> From: David Hildenbrand <david@...hat.com>
> 
> Let's have a single place (inspired by adjust_managed_page_count()) where
> we adjust present pages.
> In contrast to adjust_managed_page_count(), only memory onlining/offlining
> is allowed to modify the number of present pages.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>

Not sure self review counts ;)

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

Btw. I strongly suspect the resize lock is quite pointless here.
Something for a follow up patch.

> ---
>  mm/memory_hotplug.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 25e59d5dc13c..d05056b3c173 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -829,6 +829,16 @@ struct zone * zone_for_pfn_range(int online_type, int nid, unsigned start_pfn,
>  	return default_zone_for_pfn(nid, start_pfn, nr_pages);
>  }
>  
> +static void adjust_present_page_count(struct zone *zone, long nr_pages)
> +{
> +	unsigned long flags;
> +
> +	zone->present_pages += nr_pages;
> +	pgdat_resize_lock(zone->zone_pgdat, &flags);
> +	zone->zone_pgdat->node_present_pages += nr_pages;
> +	pgdat_resize_unlock(zone->zone_pgdat, &flags);
> +}
> +
>  int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
>  		       int online_type, int nid)
>  {
> @@ -882,11 +892,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
>  	}
>  
>  	online_pages_range(pfn, nr_pages);
> -	zone->present_pages += nr_pages;
> -
> -	pgdat_resize_lock(zone->zone_pgdat, &flags);
> -	zone->zone_pgdat->node_present_pages += nr_pages;
> -	pgdat_resize_unlock(zone->zone_pgdat, &flags);
> +	adjust_present_page_count(zone, nr_pages);
>  
>  	node_states_set_node(nid, &arg);
>  	if (need_zonelists_rebuild)
> @@ -1701,11 +1707,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
>  
>  	/* removal success */
>  	adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
> -	zone->present_pages -= nr_pages;
> -
> -	pgdat_resize_lock(zone->zone_pgdat, &flags);
> -	zone->zone_pgdat->node_present_pages -= nr_pages;
> -	pgdat_resize_unlock(zone->zone_pgdat, &flags);
> +	adjust_present_page_count(zone, -nr_pages);
>  
>  	init_per_zone_wmark_min();
>  
> -- 
> 2.16.3

-- 
Michal Hocko
SUSE Labs