linux-kernel - Re: [PATCH 4/6] mm: don't remap unused subpages when splitting isolated thp

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Message-ID: <042be214-e51c-4c69-9839-329f206dc8f8@gmail.com>
Date: Wed, 31 Jul 2024 18:08:31 +0100
From: Usama Arif <usamaarif642@...il.com>
To: Rik van Riel <riel@...riel.com>, akpm@...ux-foundation.org,
 linux-mm@...ck.org
Cc: hannes@...xchg.org, shakeel.butt@...ux.dev, roman.gushchin@...ux.dev,
 yuzhao@...gle.com, david@...hat.com, baohua@...nel.org,
 ryan.roberts@....com, rppt@...nel.org, willy@...radead.org,
 cerasuolodomenico@...il.com, corbet@....net, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, kernel-team@...a.com,
 Shuang Zhai <zhais@...gle.com>
Subject: Re: [PATCH 4/6] mm: don't remap unused subpages when splitting
 isolated thp



On 30/07/2024 19:07, Rik van Riel wrote:
> On Tue, 2024-07-30 at 13:46 +0100, Usama Arif wrote:
>>
>> +	/*
>> +	 * The pmd entry mapping the old thp was flushed and the pte
>> mapping
>> +	 * this subpage has been non present. Therefore, this
>> subpage is
>> +	 * inaccessible. We don't need to remap it if it contains
>> only zeros.
>> +	 */
>> +	addr = kmap_local_page(page);
>> +	dirty = memchr_inv(addr, 0, PAGE_SIZE);
>> +	kunmap_local(addr);
>> +
>> +	if (dirty)
>> +		return false;
>>
> 
> A minor nitpick here. The word dirty has a few different meanings
> in memory management already.
> 
> Could it be clearer to use something like "contains_data" ?
> 

Thanks, yes makes much more sense, will use contains_data in the next revision.