linux-kernel - [RFC PATCH -next 08/16] Docs/mm/damon/design: document 'address unit' parameter

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Message-ID: <20250813050706.1564229-9-yanquanmin1@huawei.com>
Date: Wed, 13 Aug 2025 13:06:58 +0800
From: Quanmin Yan <yanquanmin1@...wei.com>
To: <sj@...nel.org>
CC: <akpm@...ux-foundation.org>, <damon@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<yanquanmin1@...wei.com>, <wangkefeng.wang@...wei.com>, <zuoze1@...wei.com>
Subject: [RFC PATCH -next 08/16] Docs/mm/damon/design: document 'address unit' parameter

From: SeongJae Park <sj@...nel.org>

Add 'addr_unit' parameter description on DAMON design document.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 Documentation/mm/damon/design.rst | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 03f8137256f5..cffa320ead88 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -67,7 +67,7 @@ processes, NUMA nodes, files, and backing memory devices would be supportable.
 Also, if some architectures or devices support special optimized access check
 features, those will be easily configurable.
 
-DAMON currently provides below three operation sets.  Below two subsections
+DAMON currently provides below three operation sets.  Below three subsections
 describe how those work.
 
  - vaddr: Monitor virtual address spaces of specific processes
@@ -135,6 +135,18 @@ the interference is the responsibility of sysadmins.  However, it solves the
 conflict with the reclaim logic using ``PG_idle`` and ``PG_young`` page flags,
 as Idle page tracking does.
 
+Address Unit
+------------
+
+DAMON core layer uses ``unsinged long`` type for monitoring target address
+ranges.  In some cases, the address space for a given operations set could be
+too large to be handled with the type.  ARM (32-bit) with large physical
+address extension is an example.  For such cases, a per-operations set
+parameter called ``address unit`` is provided.  It represents the scale factor
+that need to be multiplied to the core layer's address for calculating real
+address on the given address space.  Support of ``address unit`` parameter is
+up to each operations set implementation.  ``paddr`` is the only operations set
+implementation that supports the parameter.
 
 .. _damon_core_logic:
 
-- 
2.34.1