[FFmpeg-devel] [PATCH v3] checkasm: add sample argument to adjust during bench

[J. Dekker]

Some timers on certain device and test combinations can produce noisy
results, affecting the reliability of performance measurements. One
notable example of this is the Canaan K230 RISC-V development board.

An option to adjust the number of samples by an exponent (--runs) has
been added, allowing developers to increase the sample count for more
reliable results.

Signed-off-by: J. Dekker <jdek at itanimul.li>
---
 tests/checkasm/checkasm.c | 16 +++++++++++++++-
 tests/checkasm/checkasm.h |  7 ++++---
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/tests/checkasm/checkasm.c b/tests/checkasm/checkasm.c
index 31ca9f6e2b..669f2be9c1 100644
--- a/tests/checkasm/checkasm.c
+++ b/tests/checkasm/checkasm.c
@@ -72,6 +72,9 @@
 void (*checkasm_checked_call)(void *func, int dummy, ...) = checkasm_checked_call_novfp;
 #endif
 
+/* Trade-off between speed and accuracy */
+uint64_t bench_runs = 1U << 10;
+
 /* List of tests to invoke */
 static const struct {
     const char *name;
@@ -820,7 +823,7 @@ static void bench_uninit(void)
 static int usage(const char *path)
 {
     fprintf(stderr,
-            "Usage: %s [--bench] [--test=<pattern>] [--verbose] [seed]\n",
+            "Usage: %s [--bench] [--runs=<ptwo>] [--test=<pattern>] [--verbose] [seed]\n",
             path);
     return 1;
 }
@@ -867,6 +870,17 @@ int main(int argc, char *argv[])
             state.test_name = arg + 7;
         } else if (!strcmp(arg, "--verbose") || !strcmp(arg, "-v")) {
             state.verbose = 1;
+        } else if (!strncmp(arg, "--runs=", 7)) {
+            l = strtoul(arg + 7, &end, 10);
+            if (*end == '\0') {
+                if (l > 30) {
+                    fprintf(stderr, "checkasm: error: runs exponent must be within the range 0 <= 30\n");
+                    usage(argv[0]);
+                }
+                bench_runs = 1U << l;
+            } else {
+                return usage(argv[0]);
+            }
         } else if ((l = strtoul(arg, &end, 10)) <= UINT_MAX &&
                    *end == '\0') {
             seed = l;
diff --git a/tests/checkasm/checkasm.h b/tests/checkasm/checkasm.h
index 07fcc751ff..e05053cbf6 100644
--- a/tests/checkasm/checkasm.h
+++ b/tests/checkasm/checkasm.h
@@ -167,7 +167,7 @@ extern AVLFG checkasm_lfg;
 
 static av_unused void *func_ref, *func_new;
 
-#define BENCH_RUNS 1000 /* Trade-off between accuracy and speed */
+extern uint64_t bench_runs;
 
 /* Decide whether or not the specified function needs to be tested */
 #define check_func(func, ...) (checkasm_save_context(), func_ref = checkasm_check_func((func_new = func), __VA_ARGS__))
@@ -336,10 +336,11 @@ typedef struct CheckasmPerf {
             av_unused const int sysfd = perf->sysfd;\
             func_type *tfunc = func_new;\
             uint64_t tsum = 0;\
-            int ti, tcount = 0;\
+            uint64_t ti, tcount = 0;\
             uint64_t t = 0; \
+            const uint64_t truns = bench_runs;\
             checkasm_set_signal_handler_state(1);\
-            for (ti = 0; ti < BENCH_RUNS; ti++) {\
+            for (ti = 0; ti < truns; ti++) {\
                 PERF_START(t);\
                 tfunc(__VA_ARGS__);\
                 tfunc(__VA_ARGS__);\
-- 
2.42.0