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| author | Marco Elver <elver@google.com> | 2022-03-22 14:48:25 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-22 15:57:11 -0700 |
| commit | 737b6a10ac19e41877aa1911bf6b361a72a88ad9 (patch) | |
| tree | a8e23366c9b1d6e3a5fa2220505fc175f2862a3b /Documentation/dev-tools | |
| parent | 3cb1c9620eeeb67c614c0732a35861b0b1efdc53 (diff) | |
| download | linux-737b6a10ac19e41877aa1911bf6b361a72a88ad9.tar.gz | |
kfence: allow use of a deferrable timer
Allow the use of a deferrable timer, which does not force CPU wake-ups
when the system is idle. A consequence is that the sample interval
becomes very unpredictable, to the point that it is not guaranteed that
the KFENCE KUnit test still passes.
Nevertheless, on power-constrained systems this may be preferable, so
let's give the user the option should they accept the above trade-off.
Link: https://lkml.kernel.org/r/20220308141415.3168078-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/dev-tools')
| -rw-r--r-- | Documentation/dev-tools/kfence.rst | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst index ac6b89d1a8c324..936f6aaa75c857 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 |