On Fri, Jan 23, 2026 at 04:58:37PM +0800, Feng Jiang wrote:
> 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().
...
> +static void *alloc_max_bench_buffer(struct kunit *test,
> + const size_t *lens, size_t count, size_t *buf_len)
> +{
> + size_t i, max_len = 0;
> + void *buf;
> + for (i = 0; i < count; i++) {
> + if (max_len < lens[i])
> + max_len = lens[i];
> + }
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;
> +}
...
> +#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; \
> + size_t __bn_i; \
Define it inside for-loop:s.
> + u64 __bn_t; \
> + \
> + __bn_warm_iters = max(__bn_iters / 10, 50U); \
> + \
> + for (__bn_i = 0; __bn_i < __bn_warm_iters; __bn_i++) \
> + (void)__func(__VA_ARGS__); \
> + \
> + preempt_disable(); \
> + __bn_t = ktime_get_ns(); \
> + for (__bn_i = 0; __bn_i < __bn_iters; __bn_i++) \
> + (void)__func(__VA_ARGS__); \
> + __bn_t = ktime_get_ns() - __bn_t; \
> + preempt_enable(); \
> + __bn_t; \
> +})
...
> +#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...)
> \
> +do { \
> + size_t buf_size, _bn_i, _bn_iters, _bn_size = 0; \
> + u64 _bn_t, _bn_mbps = 0, _bn_lat = 0; \
> + char *buf_name, *_bn_buf; \
> + if (!IS_ENABLED(CONFIG_STRING_KUNIT_BENCH)) \
> + kunit_skip(test, "not enabled"); \
Hmm... Since it's a macro anyway, I think the old style is okay:
#if IS_ENABLED(CONFIG_STRING_KUNIT_BENCH)
#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \
...
#else
#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \
kunit_skip(test, "not enabled"); \
#endif
But check it that it doesn't produce warnings in `make W=1` case.
> + _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++) { \
> + buf_size = bench_lens[_bn_i]; \
> + 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 * 1000; \
"KILO"? Or "(MEGA/KILO)"? I'm puzzled with this 1000 multiplier.
> + _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)
--
With Best Regards,
Andy Shevchenko
