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@igalia.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240422142007.1062231-1-mcanal@igalia.com

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 623fce7d5fcd0c4392432908e21aaba5134e3aa0..e6809b85b21105c1f07c8601f50add72f76a3da5 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4169,13 +4169,11 @@
 
        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 b1448aa81e15f48d7a2c14d18b666485635f2df1..f30a18a0e37dafb1812936731299c3b16a036664 100644 (file)
--- 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.