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[98.38.17.99]) by smtp.googlemail.com with ESMTPSA id 5614622812f47-4d5c43a24bbsm147545b6e.7.2026.09.22.11.46.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Sep 2026 11:46:08 -0700 (PDT) From: Jim Cromie Date: Tue, 22 Sep 2026 12:45:58 -0600 Subject: [PATCH v3 4/4] kallsyms: Unroll 24-bit sequence reconstruction in get_symbol_seq() Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260922-ksyms-tune-v3-4-681a34ea05d9@gmail.com> References: <20260922-ksyms-tune-v3-0-681a34ea05d9@gmail.com> In-Reply-To: <20260922-ksyms-tune-v3-0-681a34ea05d9@gmail.com> To: Andrew Morton Cc: Lorenzo Stoakes , Kees Cook , David Laight , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, bpf@vger.kernel.org, Jim Cromie X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790102761; l=1647; i=jim.cromie@gmail.com; s=20260203; h=from:subject:message-id; bh=IuMpNgCx/wsRt/giACaxjy53WAUkwMR2mJuQ09sqhYU=; b=yS/yGjzOac4hLV4AjSFZ5EelcHRPIABxP3zNa55tRBvDMQ9hjwXNYUKY/aAcVbDC1o5X/qkv+ VdoviOApkczAe37evfvRkm/lYAf+lj76e/eHBTzZCKBe70sD1vYOqhi X-Developer-Key: i=jim.cromie@gmail.com; a=ed25519; pk=C6E5ODlPQo7ZBynATXH9wg7K6HxP0pIXyf4s38Qw0XE= kallsyms_seqs_of_names[] stores 3-byte big-endian sequence indices that map alphabetical symbol positions to address-ordered symbol records. Currently, get_symbol_seq() reconstructs each 24-bit integer using a 3-iteration for-loop that shifts and bitwise-ORs each byte sequentially. During binary search in kallsyms_lookup_names() and duplicate boundary scans, this loop introduces branch and loop overhead on the hot lookup path. Mark get_symbol_seq() as static inline and unroll the 3-byte extraction into direct byte shifts: (p[0] << 16) | (p[1] << 8) | p[2]. This eliminates loop induction variable maintenance and allows the compiler to generate direct loads and constant shifts. Signed-off-by: Jim Cromie --- Changes in v3: - Added as a standalone micro-optimization patch (addresses David Laight review). --- kernel/kallsyms.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 06c79ad70cfd..8f76403e0e7b 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -281,14 +281,11 @@ unsigned long kallsyms_sym_address(int idx) return (unsigned long)offset_to_ptr(kallsyms_offsets + idx); } -static unsigned int get_symbol_seq(int index) +static inline unsigned int get_symbol_seq(int index) { - unsigned int i, seq = 0; + const u8 *p = &kallsyms_seqs_of_names[3 * index]; - for (i = 0; i < 3; i++) - seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i]; - - return seq; + return (p[0] << 16) | (p[1] << 8) | p[2]; } static int kallsyms_lookup_names(const char *name, -- 2.55.0