linux-kernel - [PATCH] mm: Update shuffle documentation to match its current state

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Date: Mon, 22 Apr 2024 11:18:40 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	David Hildenbrand <david@...hat.com>,
	Wei Yang <richard.weiyang@...ux.alibaba.com>,
	Michal Hocko <mhocko@...e.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Huang Ying <ying.huang@...el.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Dan Williams <dan.j.williams@...el.com>
Cc: linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	kernel-dev@...lia.com,
	Maíra Canal <mcanal@...lia.com>
Subject: [PATCH] mm: Update shuffle documentation to match its current state

Commit 839195352d82 ("mm/shuffle: remove dynamic reconfiguration")
removed the dynamic reconfiguration capabilities from the shuffle page
allocator. This means that, now, we don't have any perspective of an
"autodetection of memory-side-cache" that triggers the enablement of the
shuffle page allocator.

Therefore, let the documentation reflect that the only way to enable
the shuffle page allocator is by setting `page_alloc.shuffle=1`.

Signed-off-by: Maíra Canal <mcanal@...lia.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 10 ++++------
 mm/Kconfig                                      |  7 +++----
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 902ecd92a29f..924bb8ddd8a8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4170,13 +4170,11 @@
 
 	page_alloc.shuffle=
 			[KNL] Boolean flag to control whether the page allocator
-			should randomize its free lists. The randomization may
-			be automatically enabled if the kernel detects it is
-			running on a platform with a direct-mapped memory-side
-			cache, and this parameter can be used to
-			override/disable that behavior. The state of the flag
-			can be read from sysfs at:
+			should randomize its free lists. This parameter can be
+			used to enable/disable page randomization. The state of
+			the flag can be read from sysfs at:
 			/sys/module/page_alloc/parameters/shuffle.
+			This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
 
 	page_owner=	[KNL,EARLY] Boot-time page_owner enabling option.
 			Storage of the information about who allocated
diff --git a/mm/Kconfig b/mm/Kconfig
index b1448aa81e15..f30a18a0e37d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -333,10 +333,9 @@ config SHUFFLE_PAGE_ALLOCATOR
 
 	  While the randomization improves cache utilization it may
 	  negatively impact workloads on platforms without a cache. For
-	  this reason, by default, the randomization is enabled only
-	  after runtime detection of a direct-mapped memory-side-cache.
-	  Otherwise, the randomization may be force enabled with the
-	  'page_alloc.shuffle' kernel command line parameter.
+	  this reason, by default, the randomization is not enabled even
+	  if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled
+	  with the 'page_alloc.shuffle' kernel command line parameter.
 
 	  Say Y if unsure.
 
-- 
2.44.0