linux-kernel - Re: [PATCH 01/11] mm/page_alloc: Split per cpu page lists and zone stats

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Message-ID: <81cf880c-826e-6bbf-3af0-22d7aa2d3075@suse.cz>
Date:   Mon, 12 Apr 2021 19:43:18 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-RT-Users <linux-rt-users@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH 01/11] mm/page_alloc: Split per cpu page lists and zone
 stats

On 4/7/21 10:24 PM, Mel Gorman wrote:
> @@ -6691,7 +6697,7 @@ static __meminit void zone_pcp_init(struct zone *zone)
>  	 * relies on the ability of the linker to provide the
>  	 * offset of a (static) per cpu variable into the per cpu area.
>  	 */
> -	zone->pageset = &boot_pageset;
> +	zone->per_cpu_pageset = &boot_pageset;

I don't see any &boot_zonestats assignment here in zone_pcp_init() or its
caller(s), which seems strange, as zone_pcp_reset() does it.

>  	zone->pageset_high = BOOT_PAGESET_HIGH;
>  	zone->pageset_batch = BOOT_PAGESET_BATCH;
>  
> @@ -8954,17 +8960,19 @@ void zone_pcp_reset(struct zone *zone)
>  {
>  	unsigned long flags;
>  	int cpu;
> -	struct per_cpu_pageset *pset;
> +	struct per_cpu_zonestat *pzstats;
>  
>  	/* avoid races with drain_pages()  */
>  	local_irq_save(flags);
> -	if (zone->pageset != &boot_pageset) {
> +	if (zone->per_cpu_pageset != &boot_pageset) {
>  		for_each_online_cpu(cpu) {
> -			pset = per_cpu_ptr(zone->pageset, cpu);
> -			drain_zonestat(zone, pset);
> +			pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
> +			drain_zonestat(zone, pzstats);
>  		}
> -		free_percpu(zone->pageset);
> -		zone->pageset = &boot_pageset;
> +		free_percpu(zone->per_cpu_pageset);
> +		free_percpu(zone->per_cpu_zonestats);
> +		zone->per_cpu_pageset = &boot_pageset;
> +		zone->per_cpu_zonestats = &boot_zonestats;

^ here

>  	}
>  	local_irq_restore(flags);
>  }