linux-kernel - Re: [PATCH 6/9] mm, page_alloc: cache pageset high and batch in struct zone

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Date:   Wed, 7 Oct 2020 00:31:43 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Hildenbrand <david@...hat.com>, 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: [PATCH 6/9] mm, page_alloc: cache pageset high and batch in
 struct zone

On 9/25/20 12:34 PM, David Hildenbrand wrote:
> On 22.09.20 16:37, Vlastimil Babka wrote:
>> @@ -6300,6 +6310,8 @@ static __meminit void zone_pcp_init(struct zone *zone)
>>  	 * offset of a (static) per cpu variable into the per cpu area.
>>  	 */
>>  	zone->pageset = &boot_pageset;
>> +	zone->pageset_high = BOOT_PAGESET_HIGH;
>> +	zone->pageset_batch = BOOT_PAGESET_BATCH;
> 
> I do wonder if copying from any cpuvar inside boot_pageset is cleaner.
> 
> zone->pageset_high = &this_cpu_ptr(zone->pageset)->pcp.high;

Uh I don't know. That would be like admitting they can be different than what 
was initialized. But then they could be also different depending on what cpu we 
happen to run it on. It's why I added the #define BOOT_PAGESET_* in the first 
place - to ensure same value used in two places. Makes sense?