[PATCH v2 0/2] selinux: speed up avc_search_node() with large number of avc nodes

[Hongru Zhang <zhanghongru06@gmail.com>]

On mobile device high-load situations, permission check can happen
more than 90,000/s (8 core system). With default 512 cache nodes
configuration, avc cache miss happens more often and occasionally
leads to long time (>2ms) irqs off on both big and little cores,
which decreases system real-time capability.

Although we can expand avc nodes through /sys/fs/selinux/cache_threshold
to mitigate long time irqs off, hash conflicts make the bucket average
length longer because of the fixed size of cache slots, leading to
avc_search_node() latency increase.

This patch series aims to expand AVC nodes without significantly increasing
avc_search_node() latency.

This is v2 of the patch series, addressing feedback from v1.
Changes since v1:
- improve hash algorithm in avc_hash()
- define avc_cache_slots as a static variable

v1 discussion:
https://lore.kernel.org/selinux/20250905100454.685866-1-zhanghongru@xiaomi.com/

--
Hongru Zhang (2):
  selinux: Make avc cache slot size configurable during boot
  selinux: improve bucket distribution uniformity of avc_hash()

 .../admin-guide/kernel-parameters.txt         |  4 +
 security/selinux/avc.c                        | 82 ++++++++++++++-----
 2 files changed, 64 insertions(+), 22 deletions(-)


base-commit: 68e1e908cb7682db9fb7f79907f9352435a81c0f
-- 
2.43.0