From nobody Tue Feb 10 05:26:33 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 6B4C137FF74; Tue, 13 Jan 2026 08:28:32 +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=1768292914; cv=none; b=A+mTVOndEH3G49A3b6pViYyBYJXzoOUIl7zjHdtf0pXZMAjP2/4j2pYylI9g7ZK5sxvphXlzcobhnmkXnpi8YOMApHlp2f7JlFba4KSUWDdvNnbxslOmMGTMt/7HRXcpXtH6Jtm54Te2YQW3IsxB/QumrRDKLBCqt500kcST6jQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768292914; c=relaxed/simple; bh=4kYWroEgbC/TDWO7MGq5upkrX8k6YjNkSysCjVjfssc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=eKVjEXKXF+E4ugehELMMvay9SoHC1zGRa548nhurxjb+eBvaj2UcvQnWrTB/GqooDaeIGN7sca4naTf8ikWZ3Jt2nOVJwFpVAdQMQHqO7agmh6oDnxWHNPdo4heJdodTc60+7pM1Z7VK49yWwvxSqBB02XVvcKHBM30FtP3w2j0= 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: d5918680f05911f0a38c85956e01ac42-20260113 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.6,REQID:50dd73d7-9d29-46a9-882c-f5c7f518d278,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:2bf60e9b387b1767bb21e51aed26440f,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: d5918680f05911f0a38c85956e01ac42-20260113 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 2104796398; Tue, 13 Jan 2026 16:28:27 +0800 From: Feng Jiang To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, kees@kernel.org, andy@kernel.org, akpm@linux-foundation.org, jiangfeng@kylinos.cn, ebiggers@kernel.org, martin.petersen@oracle.com, ardb@kernel.org, ajones@ventanamicro.com, conor.dooley@microchip.com, samuel.holland@sifive.com, linus.walleij@linaro.org, nathan@kernel.org Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2 08/14] lib/string_kunit: add performance benchmark for strlen() Date: Tue, 13 Jan 2026 16:27:42 +0800 Message-Id: <20260113082748.250916-9-jiangfeng@kylinos.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260113082748.250916-1-jiangfeng@kylinos.cn> References: <20260113082748.250916-1-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 benchmark to compare the architecture-optimized strlen() implementation against the generic C version (__generic_strlen). The benchmark uses a table-driven approach to evaluate performance across different string lengths (short, medium, and long). It employs ktime_get() for timing and get_random_bytes() followed by null-byte filtering to generate test data that prevents early termination. This helps in quantifying the performance gains of architecture-specific optimizations on various platforms. Suggested-by: Andy Shevchenko Signed-off-by: Feng Jiang --- lib/tests/string_kunit.c | 117 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c index 8eb095404b95..2266954ae5e0 100644 --- a/lib/tests/string_kunit.c +++ b/lib/tests/string_kunit.c @@ -20,6 +20,77 @@ #define STRING_TEST_MAX_LEN 128 #define STRING_TEST_MAX_OFFSET 16 =20 +#if defined(__HAVE_ARCH_STRLEN) +#define STRING_BENCH_ENABLED +#endif + +#ifdef STRING_BENCH_ENABLED +/* Configuration for string benchmark scenarios */ +struct string_bench_case { + const char *name; + size_t len; + unsigned int iterations; +}; + +static const struct string_bench_case bench_cases[] =3D { + {"short", 8, 100000}, + {"medium", 64, 100000}, + {"long", 2048, 10000}, +}; + +/** + * get_max_bench_len() - Get the maximum length from benchmark cases + * @cases: array of test cases + * @count: number of cases + */ +static size_t get_max_bench_len(const struct string_bench_case *cases, siz= e_t count) +{ + size_t i, max_len =3D 0; + + for (i =3D 0; i < count; i++) { + if (cases[i].len > max_len) + max_len =3D cases[i].len; + } + + return max_len; +} + +/** + * get_random_nonzero_bytes() - Fill buffer with random non-null bytes + * @buf: buffer to fill + * @len: number of bytes to fill + */ +static void get_random_nonzero_bytes(void *buf, size_t len) +{ + u8 *s =3D (u8 *)buf; + + get_random_bytes(buf, len); + + /* Replace null bytes to avoid early string termination */ + for (size_t i =3D 0; i < len; i++) { + if (s[i] =3D=3D '\0') + s[i] =3D 0x01; + } +} + +static void string_bench_report(struct kunit *test, const char *func, + const struct string_bench_case *bc, + u64 time_arch, u64 time_generic) +{ + u64 ratio_int, ratio_frac; + + /* Calculate speedup ratio with 2 decimal places. */ + ratio_int =3D div64_u64(time_generic, time_arch); + ratio_frac =3D div64_u64((time_generic % time_arch) * 100, time_arch); + + kunit_info(test, "%s performance (%s, len: %zu, iters: %u):\n", + func, bc->name, bc->len, bc->iterations); + kunit_info(test, " arch-optimized: %llu ns\n", time_arch); + kunit_info(test, " generic C: %llu ns\n", time_generic); + kunit_info(test, " speedup: %llu.%02llux\n", ratio_int, ratio_fra= c); +} +#endif /* STRING_BENCH_ENABLED */ + static void string_test_memset16(struct kunit *test) { unsigned i, j, k; @@ -129,6 +200,49 @@ static void string_test_strlen(struct kunit *test) } } =20 +#ifdef __HAVE_ARCH_STRLEN +static void string_test_strlen_bench(struct kunit *test) +{ + char *buf; + size_t buf_len, iters; + ktime_t start, end; + u64 time_arch, time_generic; + + buf_len =3D get_max_bench_len(bench_cases, ARRAY_SIZE(bench_cases)) + 1; + + buf =3D kunit_kzalloc(test, buf_len, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf); + + for (size_t i =3D 0; i < ARRAY_SIZE(bench_cases); i++) { + get_random_nonzero_bytes(buf, bench_cases[i].len); + buf[bench_cases[i].len] =3D '\0'; + + iters =3D bench_cases[i].iterations; + + /* 1. Benchmark the architecture-optimized version */ + start =3D ktime_get(); + for (unsigned int j =3D 0; j < iters; j++) { + OPTIMIZER_HIDE_VAR(buf); + (void)strlen(buf); + } + end =3D ktime_get(); + time_arch =3D ktime_to_ns(ktime_sub(end, start)); + + /* 2. Benchmark the generic C version */ + start =3D ktime_get(); + for (unsigned int j =3D 0; j < iters; j++) { + OPTIMIZER_HIDE_VAR(buf); + (void)__generic_strlen(buf); + } + end =3D ktime_get(); + time_generic =3D ktime_to_ns(ktime_sub(end, start)); + + string_bench_report(test, "strlen", &bench_cases[i], + time_arch, time_generic); + } +} +#endif + static void string_test_strnlen(struct kunit *test) { char *s; @@ -702,6 +816,9 @@ static struct kunit_case string_test_cases[] =3D { KUNIT_CASE(string_test_memset32), KUNIT_CASE(string_test_memset64), KUNIT_CASE(string_test_strlen), +#ifdef __HAVE_ARCH_STRLEN + KUNIT_CASE(string_test_strlen_bench), +#endif KUNIT_CASE(string_test_strnlen), KUNIT_CASE(string_test_strchr), KUNIT_CASE(string_test_strnchr), --=20 2.25.1