From nobody Mon Feb 9 19:25:58 2026 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D49632D47EA; Tue, 20 Jan 2026 06:59:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768892369; cv=none; b=I5c53fzNl5EqhEde806mmcmEwJl6sslDX1V2KLs+26qXW0jcG9MiRqEDCA2TOautiNJdtaFSJLR93YWwpektMQ6djlQoYOMUdtv3xECljrjet35ihPO9QnJO8dE5IliQIpfPyEcWS+8WwblMwjX153kat+LJ42pkfOMZleugn54= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768892369; c=relaxed/simple; bh=Jsi1e7C//bWQNdJn4UsweF9WkeTYnrxFL4Y45i9D2pQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=KVRgKYflq2/yiyomh9EtQvBmSiz0KFOK51b1kg0UpwARmPapH7q8NcOYX+Ix4eeukJmVR8INjBgVxgZAEVzFDbhC0CntiiSdn56hQMvrMyZ5iPInpUyzulaqs+plmapij8kb87QxU6R1w9hiNdBRuQlicsgL7chbf1TnsBPLia0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 7f779af4f5cd11f0b0f03b4cfa9209d1-20260120 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.6,REQID:0ce710d8-dd33-4617-be18-b53201a1f140,IP:0,UR L:0,TC:0,Content:-25,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:-25 X-CID-META: VersionHash:a9d874c,CLOUDID:8ee1a22fec7a92a4a5b841f6a89d7dcc,BulkI D:nil,BulkQuantity:0,Recheck:0,SF:81|82|102|850|898,TC:nil,Content:0|15|50 ,EDM:-3,IP:nil,URL:0,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,O SA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 7f779af4f5cd11f0b0f03b4cfa9209d1-20260120 X-User: jiangfeng@kylinos.cn Received: from localhost.localdomain [(10.44.16.150)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 863038979; Tue, 20 Jan 2026 14:59:00 +0800 From: Feng Jiang To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, akpm@linux-foundation.org, kees@kernel.org, andy@kernel.org, jiangfeng@kylinos.cn, ebiggers@kernel.org, martin.petersen@oracle.com, ardb@kernel.org, charlie@rivosinc.com, conor.dooley@microchip.com, ajones@ventanamicro.com, linus.walleij@linaro.org, nathan@kernel.org Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Joel Stanley Subject: [PATCH v3 4/8] lib/string_kunit: add performance benchmarks for strlen Date: Tue, 20 Jan 2026 14:58:48 +0800 Message-Id: <20260120065852.166857-5-jiangfeng@kylinos.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260120065852.166857-1-jiangfeng@kylinos.cn> References: <20260120065852.166857-1-jiangfeng@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Introduce a benchmarking framework to the string_kunit test suite to measure the execution efficiency of string functions. The implementation is inspired by crc_benchmark(), measuring throughput (MB/s) and latency (ns/call) across a range of string lengths. It includes a warm-up phase, disables preemption during measurement, and uses a fixed seed for reproducible results. This allows for comparing different implementations (e.g., generic C vs. architecture-optimized assembly) within the KUnit environment. Initially, provide benchmarks for strlen(). Suggested-by: Andy Shevchenko Suggested-by: Eric Biggers Tested-by: Joel Stanley Signed-off-by: Feng Jiang --- lib/Kconfig.debug | 11 +++ lib/tests/string_kunit.c | 151 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 162 insertions(+) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ba36939fda79..21b058ae815f 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2475,6 +2475,17 @@ config STRING_HELPERS_KUNIT_TEST depends on KUNIT default KUNIT_ALL_TESTS =20 +config STRING_KUNIT_BENCH + bool "Benchmark string functions at runtime" + depends on STRING_KUNIT_TEST + help + Enable performance measurement for string functions. + + This measures the execution efficiency of string functions + during the KUnit test run. + + If unsure, say N. + config FFS_KUNIT_TEST tristate "KUnit test ffs-family functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c index 8f836847a80e..e20e924d1c67 100644 --- a/lib/tests/string_kunit.c +++ b/lib/tests/string_kunit.c @@ -6,7 +6,9 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt =20 #include +#include #include +#include #include #include #include @@ -20,6 +22,9 @@ #define STRING_TEST_MAX_LEN 128 #define STRING_TEST_MAX_OFFSET 16 =20 +#define STRING_BENCH_SEED 888 +#define STRING_BENCH_WORKLOAD 1000000UL + static void string_test_memset16(struct kunit *test) { unsigned i, j, k; @@ -700,6 +705,151 @@ static void string_test_strends(struct kunit *test) KUNIT_EXPECT_TRUE(test, strends("", "")); } =20 +/* Target string lengths for benchmarking */ +static const size_t bench_lens[] =3D { + 0, 1, 7, 8, 16, 31, 64, 127, 512, 1024, 3173, 4096 +}; + +/** + * alloc_max_bench_buffer() - Allocate buffer for the max test case. + * @test: KUnit context for managed allocation. + * @lens: Array of lengths used in the benchmark cases. + * @count: Number of elements in the @lens array. + * @buf_len: [out] Pointer to store the actually allocated buffer + * size (including null). + * + * Return: Pointer to the allocated memory, or NULL on failure. + */ +static void *alloc_max_bench_buffer(struct kunit *test, + const size_t *lens, size_t count, size_t *buf_len) +{ + void *buf; + size_t i, max_len =3D 0; + + for (i =3D 0; i < count; i++) { + if (max_len < lens[i]) + max_len =3D lens[i]; + } + + /* Add space for NUL terminator */ + max_len +=3D 1; + + buf =3D kunit_kzalloc(test, max_len, GFP_KERNEL); + if (buf && buf_len) + *buf_len =3D max_len; + + return buf; +} + +/** + * fill_random_string() - Fill buffer with random non-null bytes. + * @buf: Buffer to fill. + * @len: Number of bytes to fill. + */ +static void fill_random_string(char *buf, size_t len) +{ + size_t i; + struct rnd_state state; + + if (!buf || !len) + return; + + /* Use a fixed seed to ensure deterministic benchmark results */ + prandom_seed_state(&state, 888); + prandom_bytes_state(&state, buf, len); + + /* Replace null bytes to avoid early string termination */ + for (i =3D 0; i < len; i++) { + if (buf[i] =3D=3D '\0') + buf[i] =3D 0x01; + } + + buf[len - 1] =3D '\0'; +} + +/** + * STRING_BENCH() - Benchmark string functions. + * @iters: Number of iterations to run. + * @func: Function to benchmark. + * @...: Variable arguments passed to @func. + * + * Disables preemption and measures the total time in nanoseconds to execu= te + * @func(@__VA_ARGS__) for @iters times, including a small warm-up phase. + * + * Context: Disables preemption during measurement. + * Return: Total execution time in nanoseconds (u64). + */ +#define STRING_BENCH(iters, func, ...) \ +({ \ + u64 __bn_t; \ + size_t __bn_i; \ + size_t __bn_iters =3D (iters); \ + size_t __bn_warm_iters =3D max_t(size_t, __bn_iters / 10, 50U); \ + /* Volatile function pointer prevents dead code elimination */ \ + typeof(func) (* volatile __func) =3D (func); \ + \ + for (__bn_i =3D 0; __bn_i < __bn_warm_iters; __bn_i++) \ + (void)__func(__VA_ARGS__); \ + \ + preempt_disable(); \ + __bn_t =3D ktime_get_ns(); \ + for (__bn_i =3D 0; __bn_i < __bn_iters; __bn_i++) \ + (void)__func(__VA_ARGS__); \ + __bn_t =3D ktime_get_ns() - __bn_t; \ + preempt_enable(); \ + __bn_t; \ +}) + +/** + * STRING_BENCH_BUF() - Benchmark harness for single-buffer functions. + * @test: KUnit context. + * @buf_name: Local char * variable name to be defined. + * @buf_size: Local size_t variable name to be defined. + * @func: Function to benchmark. + * @...: Extra arguments for @func. + * + * Prepares a randomized, null-terminated buffer and iterates through leng= ths + * in bench_lens, defining @buf_name and @buf_size in each loop. + */ +#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ +do { \ + char *buf_name, *_bn_buf; \ + size_t buf_size, _bn_i, _bn_iters, _bn_size =3D 0; \ + u64 _bn_t, _bn_mbps =3D 0, _bn_lat =3D 0; \ + \ + if (!IS_ENABLED(CONFIG_STRING_KUNIT_BENCH)) \ + kunit_skip(test, "not enabled"); \ + \ + _bn_buf =3D alloc_max_bench_buffer(test, bench_lens, \ + ARRAY_SIZE(bench_lens), &_bn_size); \ + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, _bn_buf); \ + \ + fill_random_string(_bn_buf, _bn_size); \ + _bn_buf[_bn_size - 1] =3D '\0'; \ + \ + for (_bn_i =3D 0; _bn_i < ARRAY_SIZE(bench_lens); _bn_i++) { \ + buf_size =3D bench_lens[_bn_i]; \ + buf_name =3D _bn_buf + _bn_size - buf_size - 1; \ + _bn_iters =3D STRING_BENCH_WORKLOAD / \ + max_t(size_t, buf_size, 1U); \ + \ + _bn_t =3D STRING_BENCH(_bn_iters, func, ##__VA_ARGS__); \ + \ + if (_bn_t > 0) { \ + _bn_mbps =3D (u64)(buf_size) * _bn_iters * 1000; \ + _bn_mbps =3D div64_u64(_bn_mbps, _bn_t); \ + _bn_lat =3D div64_u64(_bn_t, _bn_iters); \ + } \ + kunit_info(test, "len=3D%zu: %llu MB/s (%llu ns/call)\n", \ + buf_size, _bn_mbps, _bn_lat); \ + } \ +} while (0) + +static void string_bench_strlen(struct kunit *test) +{ + STRING_BENCH_BUF(test, buf, len, strlen, buf); +} + static struct kunit_case string_test_cases[] =3D { KUNIT_CASE(string_test_memset16), KUNIT_CASE(string_test_memset32), @@ -725,6 +875,7 @@ static struct kunit_case string_test_cases[] =3D { KUNIT_CASE(string_test_strtomem), KUNIT_CASE(string_test_memtostr), KUNIT_CASE(string_test_strends), + KUNIT_CASE(string_bench_strlen), {} }; =20 --=20 2.25.1