linux-kernel - Re: [RFC PATCH 3/6] mm: page_owner: add support for splitting to any order in split page

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Date:   Tue, 17 Nov 2020 16:13:27 -0500
From:   Zi Yan <ziy@...dia.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <linux-mm@...ck.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Roman Gushchin <guro@...com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        Yang Shi <shy828301@...il.com>,
        "Michal Hocko" <mhocko@...nel.org>,
        John Hubbard <jhubbard@...dia.com>,
        "Ralph Campbell" <rcampbell@...dia.com>,
        David Nellans <dnellans@...dia.com>
Subject: Re: [RFC PATCH 3/6] mm: page_owner: add support for splitting to any
 order in split page_owner.

On 17 Nov 2020, at 16:10, Matthew Wilcox wrote:

> On Wed, Nov 11, 2020 at 03:40:05PM -0500, Zi Yan wrote:
>> -	for (i = 0; i < nr; i++) {
>> +	for (i = 0; i < nr; i += (1 << new_order)) {
>>  		page_owner = get_page_owner(page_ext);
>> -		page_owner->order = 0;
>> +		page_owner->order = new_order;
>>  		page_ext = page_ext_next(page_ext);
>>  	}
>
> This doesn't do what you're hoping it will.  It's going to set ->order to
> new_order for the first N pages instead of every 1/N pages.
>
> You'll need to do something like
>
> 		page_ext = lookup_page_ext(page + i);

Will use this. Thanks.

>
> or add a new page_ext_add(page_ext, 1 << new_order);


—
Best Regards,
Yan Zi

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