linux-kernel - [RFC PATCH 1/6] mm: introduce SELECTIVE

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Message-ID: <20250321173729.3175898-2-souravpanda@google.com>
Date: Fri, 21 Mar 2025 17:37:24 +0000
From: Sourav Panda <souravpanda@...gle.com>
To: mathieu.desnoyers@...icios.com, willy@...radead.org, david@...hat.com, 
	pasha.tatashin@...een.com, rientjes@...gle.com, akpm@...ux-foundation.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, weixugc@...gle.com, 
	gthelen@...gle.com, souravpanda@...gle.com, surenb@...gle.com
Subject: [RFC PATCH 1/6] mm: introduce SELECTIVE_KSM KConfig

Gate the partitioned and synchronous features of SELECTIVE_KSM behind
a KConfig. This shall prevent vanilla KSM's background thread from
stepping over SELECTIVE_KSM.

Signed-off-by: Sourav Panda <souravpanda@...gle.com>
---
 mm/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 1b501db06417..f9873002414c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -783,6 +783,17 @@ config KSM
 	  until a program has madvised that an area is MADV_MERGEABLE, and
 	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 
+config SELECTIVE_KSM
+	bool "Enable Selective KSM for page merging"
+	depends on KSM
+	help
+	  Enable Synchronous and Partitioned KSM for page merging. There is
+	  no background scanning. Instead, userspace specifies the pid
+	  and address range to have merged. The partitioning aspect divides
+	  the merge space into security domains. Merging of pages only takes
+	  place within a partition, improving security. Furthermore, trees
+	  in each partitioning becomes smaller, improving CPU efficiency.
+
 config DEFAULT_MMAP_MIN_ADDR
 	int "Low address space to protect from user allocation"
 	depends on MMU
-- 
2.49.0.395.g12beb8f557-goog