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[71.126.255.178]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-87f9e7f52e1sm22984526d6.51.2025.10.23.15.24.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Oct 2025 15:24:28 -0700 (PDT) Date: Thu, 23 Oct 2025 18:24:27 -0400 Message-ID: <5fa2cff3acf5ae62cb76f157fb36b7a8@paul-moore.com> Precedence: bulk X-Mailing-List: selinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Mailer: pstg-pwork:20251022_1923/pstg-lib:20251023_1801/pstg-pwork:20251022_1923 From: Paul Moore To: Hongru Zhang , stephen.smalley.work@gmail.com, omosnace@redhat.com Cc: linux-kernel@vger.kernel.org, selinux@vger.kernel.org, zhanghongru@xiaomi.com Subject: Re: [PATCH v4 3/3] selinux: improve bucket distribution uniformity of avc_hash() References: <4bf4246da1ad44670093e006bffd3c9e07f089ea.1761217900.git.zhanghongru@xiaomi.com> In-Reply-To: <4bf4246da1ad44670093e006bffd3c9e07f089ea.1761217900.git.zhanghongru@xiaomi.com> On Oct 23, 2025 Hongru Zhang wrote: > > Reuse the already implemented MurmurHash3 algorithm. Under heavy stress > testing (on an 8-core system sustaining over 50,000 authentication events > per second), sample once per second and take the mean of 1800 samples: > > 1. Bucket utilization rate and length of longest chain > +--------------------------+-----------------------------------------+ > | | bucket utilization rate / longest chain | > | +--------------------+--------------------+ > | | no-patch | with-patch | > +--------------------------+--------------------+--------------------+ > | 512 nodes, 512 buckets | 52.5%/7.5 | 60.2%/5.7 | > +--------------------------+--------------------+--------------------+ > | 1024 nodes, 512 buckets | 68.9%/12.1 | 80.2%/9.7 | > +--------------------------+--------------------+--------------------+ > | 2048 nodes, 512 buckets | 83.7%/19.4 | 93.4%/16.3 | > +--------------------------+--------------------+--------------------+ > | 8192 nodes, 8192 buckets | 49.5%/11.4 | 60.3%/7.4 | > +--------------------------+--------------------+--------------------+ > > 2. avc_search_node latency (total latency of hash operation and table > lookup) > +--------------------------+-----------------------------------------+ > | | latency of function avc_search_node | > | +--------------------+--------------------+ > | | no-patch | with-patch | > +--------------------------+--------------------+--------------------+ > | 512 nodes, 512 buckets | 87ns | 84ns | > +--------------------------+--------------------+--------------------+ > | 1024 nodes, 512 buckets | 97ns | 96ns | > +--------------------------+--------------------+--------------------+ > | 2048 nodes, 512 buckets | 118ns | 113ns | > +--------------------------+--------------------+--------------------+ > | 8192 nodes, 8192 buckets | 106ns | 99ns | > +--------------------------+--------------------+--------------------+ > > Although MurmurHash3 has higher overhead than the bitwise operations in > the original algorithm, the data shows that the MurmurHash3 achieves > better distribution, reducing average lookup time. Consequently, the > total latency of hashing and table lookup is lower than before. > > Signed-off-by: Hongru Zhang > --- > security/selinux/avc.c | 3 ++- > security/selinux/include/hash.h | 11 ++++++----- > security/selinux/ss/avtab.c | 6 ++++++ > 3 files changed, 14 insertions(+), 6 deletions(-) Merged into selinux/dev, thanks! -- paul-moore.com