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| author |   Marco Elver <elver@google.com> | 2021-11-05 13:45:37 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2021-11-06 13:30:43 -0700 |
| commit | 5cc906b4b4a510b274113ddb3f88d60644553f79 (patch) | |
| tree | f044488fbfa53b5fcad9ca70979b77ddd9f4a87b /Documentation/dev-tools | |
| parent | kfence: limit currently covered allocations when pool nearly full (diff) | |
| download | linux-dev-5cc906b4b4a510b274113ddb3f88d60644553f79.tar.xz linux-dev-5cc906b4b4a510b274113ddb3f88d60644553f79.zip | |
kfence: add note to documentation about skipping covered allocations
Add a note briefly mentioning the new policy about "skipping currently
covered allocations if pool close to full." Since this has a notable
impact on KFENCE's bug-detection ability on systems with large uptimes,
it is worth pointing out the feature.
Link: https://lkml.kernel.org/r/20210923104803.2620285-5-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Alexander Potapenko <glider@google.com>
Cc: Aleksandr Nogikh <nogikh@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Taras Madan <tarasmadan@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 | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst index 0fbe3308bf37..d45f952986ae 100644 --- a/Documentation/dev-tools/kfence.rst +++ b/Documentation/dev-tools/kfence.rst @@ -269,6 +269,17 @@ tail of KFENCE's freelist, so that the least recently freed objects are reused first, and the chances of detecting use-after-frees of recently freed objects is increased. +If pool utilization reaches 75% (default) or above, to reduce the risk of the +pool eventually being fully occupied by allocated objects yet ensure diverse +coverage of allocations, KFENCE limits currently covered allocations of the +same source from further filling up the pool. The "source" of an allocation is +based on its partial allocation stack trace. A side-effect is that this also +limits frequent long-lived allocations (e.g. pagecache) of the same source +filling up the pool permanently, which is the most common risk for the pool +becoming full and the sampled allocation rate dropping to zero. The threshold +at which to start limiting currently covered allocations can be configured via +the boot parameter ``kfence.skip_covered_thresh`` (pool usage%). + Interface --------- |