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diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst
index ac6b89d1a8c3..936f6aaa75c8 100644
--- a/Documentation/dev-tools/kfence.rst
+++ b/Documentation/dev-tools/kfence.rst
@@ -41,6 +41,18 @@ guarded by KFENCE. The default is configurable via the Kconfig option
``CONFIG_KFENCE_SAMPLE_INTERVAL``. Setting ``kfence.sample_interval=0``
disables KFENCE.
+The sample interval controls a timer that sets up KFENCE allocations. By
+default, to keep the real sample interval predictable, the normal timer also
+causes CPU wake-ups when the system is completely idle. This may be undesirable
+on power-constrained systems. The boot parameter ``kfence.deferrable=1``
+instead switches to a "deferrable" timer which does not force CPU wake-ups on
+idle systems, at the risk of unpredictable sample intervals. The default is
+configurable via the Kconfig option ``CONFIG_KFENCE_DEFERRABLE``.
+
+.. warning::
+ The KUnit test suite is very likely to fail when using a deferrable timer
+ since it currently causes very unpredictable sample intervals.
+
The KFENCE memory pool is of fixed size, and if the pool is exhausted, no
further KFENCE allocations occur. With ``CONFIG_KFENCE_NUM_OBJECTS`` (default
255), the number of available guarded objects can be controlled. Each object