linux-kernel - Re: [PATCH v5 12/14] mm: add config option for clearing page-extents

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Message-Id: <20250710005835.8819c30579e37b90d79f4c53@linux-foundation.org>
Date: Thu, 10 Jul 2025 00:58:35 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
 david@...hat.com, 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, raghavendra.kt@....com, boris.ostrovsky@...cle.com,
 konrad.wilk@...cle.com
Subject: Re: [PATCH v5 12/14] mm: add config option for clearing
 page-extents

On Wed,  9 Jul 2025 17:59:24 -0700 Ankur Arora <ankur.a.arora@...cle.com> wrote:

> This is only available with !CONFIG_HIGHMEM because the intent is to
> use architecture support to clear contiguous extents in a single
> operation (ex. via FEAT_MOPS on arm64, string instructions on x86)
> which excludes any possibility of interspersing kmap()/kunmap().

I'm feeling dumb.  What does the use of a string instruction have to do
with kmap/kunmap?