linux-kernel - Re: [PATCH v5 13/14] mm: memory: support clearing page-extents

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Message-ID: <298b6a09-1b77-43a7-82f2-f362d3104f71@amd.com>
Date: Fri, 11 Jul 2025 18:57:08 +0530
From: Raghavendra K T <raghavendra.kt@....com>
To: David Hildenbrand <david@...hat.com>,
 Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, bp@...en8.de, dave.hansen@...ux.intel.com,
 hpa@...or.com, mingo@...hat.com, mjguzik@...il.com, luto@...nel.org,
 peterz@...radead.org, acme@...nel.org, namhyung@...nel.org,
 tglx@...utronix.de, willy@...radead.org, boris.ostrovsky@...cle.com,
 konrad.wilk@...cle.com
Subject: Re: [PATCH v5 13/14] mm: memory: support clearing page-extents


On 7/11/2025 5:14 PM, David Hildenbrand wrote:
> On 10.07.25 02:59, Ankur Arora wrote:
>> folio_zero_user() is constrained to clear in a page-at-a-time
>> fashion because it supports CONFIG_HIGHMEM which means that kernel
>> mappings for pages in a folio are not guaranteed to be contiguous.
>>
>> We don't have this problem when running under configurations with
>> CONFIG_CLEAR_PAGE_EXTENT (implies !CONFIG_HIGHMEM), so zero in
>> longer page-extents.
>> This is expected to be faster because the processor can now optimize
>> the clearing based on the knowledge of the extent.
>>
> 
> I'm curious: how did we end up "page extent" terminology? :)
> 
> "CONFIG_CLEAR_CONTIG_PAGES" or sth. like that would be a bit clearer 
> (pun intended), at least to me.
> 

How about CONFIG_CLEAR_MULTI_PAGE ?

> We use "CONTIG" pages already in different MM context.
> 
> "page extent" reminds of "page_ext", which is "page extension" ...
> 
[...]

- Raghu