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 framework allows for comparing different implementations (e.g., generic C vs. architecture-optimized assembly) within the KUnit environment. Initially, provide a benchmark for strlen(). Suggested-by: Andy Shevchenko <[email protected]> Suggested-by: Eric Biggers <[email protected]> Signed-off-by: Feng Jiang <[email protected]> --- lib/Kconfig.debug | 11 +++ lib/tests/string_kunit.c | 160 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 171 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 +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 f16dfa29e8ce..4636379c6d5c 100644 --- a/lib/tests/string_kunit.c +++ b/lib/tests/string_kunit.c @@ -6,10 +6,16 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <kunit/test.h> +#include <linux/ktime.h> +#include <linux/math64.h> +#include <linux/minmax.h> #include <linux/module.h> +#include <linux/prandom.h> #include <linux/printk.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/time64.h> +#include <linux/units.h> #include <linux/vmalloc.h> #define STRCMP_LARGE_BUF_LEN 2048 @@ -21,6 +27,9 @@ #define STRING_TEST_MAX_LEN 128 #define STRING_TEST_MAX_OFFSET 16 +#define STRING_BENCH_SEED 888 +#define STRING_BENCH_WORKLOAD (1 * MEGA) + static void string_test_memset16(struct kunit *test) { unsigned i, j, k; @@ -706,6 +715,156 @@ static void string_test_strends(struct kunit *test) KUNIT_EXPECT_TRUE(test, strends("", "")); } +#if IS_ENABLED(CONFIG_STRING_KUNIT_BENCH) +/* Target string lengths for benchmarking */ +static const size_t bench_lens[] = { + 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 NUL character). + * + * 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) +{ + size_t max_len = 0; + void *buf; + + for (size_t i = 0; i < count; i++) + max_len = max(lens[i], max_len); + + /* Add space for NUL character */ + max_len += 1; + + buf = kunit_kzalloc(test, max_len, GFP_KERNEL); + if (!buf) + return NULL; + + if (buf_len) + *buf_len = max_len; + + return buf; +} + +/** + * fill_random_string() - Populate a buffer with a random NUL-terminated string. + * @buf: Buffer to fill. + * @len: Length of the buffer in bytes. + * + * Fills the buffer with random non-NUL bytes and ensures the string is + * properly NUL-terminated. + */ +static void fill_random_string(char *buf, size_t len) +{ + struct rnd_state state; + + if (!buf || !len) + return; + + /* Use a fixed seed to ensure deterministic benchmark results */ + prandom_seed_state(&state, STRING_BENCH_SEED); + prandom_bytes_state(&state, buf, len); + + /* Replace NUL characters to avoid early string termination */ + for (size_t i = 0; i < len; i++) { + if (buf[i] == '\0') + buf[i] = 0x01; + } + + buf[len - 1] = '\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 execute + * @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, ...) \ +({ \ + /* Volatile function pointer prevents dead code elimination */ \ + typeof(func) (* volatile __func) = (func); \ + size_t __bn_iters = (iters); \ + size_t __bn_warm_iters; \ + u64 __bn_t; \ + \ + /* Use 10% of the given iterations (maximum 50) to warm up */ \ + __bn_warm_iters = max(__bn_iters / 10, 50U); \ + \ + for (size_t __bn_i = 0; __bn_i < __bn_warm_iters; __bn_i++) \ + (void)__func(__VA_ARGS__); \ + \ + preempt_disable(); \ + __bn_t = ktime_get_ns(); \ + for (size_t __bn_i = 0; __bn_i < __bn_iters; __bn_i++) \ + (void)__func(__VA_ARGS__); \ + __bn_t = 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, NUL-terminated buffer and iterates through lengths + * in bench_lens, defining @buf_name and @buf_size in each loop. + */ +#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ +do { \ + size_t _bn_i, _bn_iters, _bn_size = 0; \ + u64 _bn_t, _bn_mbps = 0, _bn_lat = 0; \ + char *_bn_buf; \ + \ + _bn_buf = 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); \ + \ + for (_bn_i = 0; _bn_i < ARRAY_SIZE(bench_lens); _bn_i++) { \ + size_t buf_size = bench_lens[_bn_i]; \ + char *buf_name = _bn_buf + _bn_size - buf_size - 1; \ + _bn_iters = STRING_BENCH_WORKLOAD / max(buf_size, 1U); \ + \ + _bn_t = STRING_BENCH(_bn_iters, func, ##__VA_ARGS__); \ + if (_bn_t > 0) { \ + _bn_mbps = (u64)(buf_size) * _bn_iters * \ + (NSEC_PER_SEC / MEGA); \ + _bn_mbps = div64_u64(_bn_mbps, _bn_t); \ + _bn_lat = div64_u64(_bn_t, _bn_iters); \ + } \ + kunit_info(test, "len=%zu: %llu MB/s (%llu ns/call)\n", \ + buf_size, _bn_mbps, _bn_lat); \ + } \ +} while (0) +#else +#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ + kunit_skip(test, "not enabled") +#endif /* IS_ENABLED(CONFIG_STRING_KUNIT_BENCH) */ + +static void string_bench_strlen(struct kunit *test) +{ + STRING_BENCH_BUF(test, buf, len, strlen, buf); +} + static struct kunit_case string_test_cases[] = { KUNIT_CASE(string_test_memset16), KUNIT_CASE(string_test_memset32), @@ -731,6 +890,7 @@ static struct kunit_case string_test_cases[] = { KUNIT_CASE(string_test_strtomem), KUNIT_CASE(string_test_memtostr), KUNIT_CASE(string_test_strends), + KUNIT_CASE(string_bench_strlen), {} }; -- 2.25.1
