From: Marco Elver elver@google.com
mainline inclusion from mainline-v5.16-rc1 commit 5cc906b4b4a510b274113ddb3f88d60644553f79 category: feature bugzilla: 185780 https://gitee.com/openeuler/kernel/issues/I4EUY7
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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 Signed-off-by: Peng Liu liupeng256@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- Documentation/dev-tools/kfence.rst | 11 +++++++++++ 1 file changed, 11 insertions(+)
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 ---------