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Drop workload phase recording and slow telemetry sampling to 2/sec

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The telemetry thread's per-core /sys scan was contending with the
timed benchmark passes, and could corrupt the workload-size
calibration step, causing run-to-run swings of up to 4x. Removing
phase recording and dropping the sample rate from 4/sec to 2/sec
brings runs back to <5% variance.
This commit is contained in:
owen
2026-07-21 00:29:39 -05:00
parent 042c839751
commit 31ec0f67e0
2 changed files with 4 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/app/benchmark.c
+4 -27
View File
@@ -173,6 +173,8 @@ extern uint64_t fb_c_chase(void **ptrs, uint64_t steps);
# define REPEATS 3 /* Number of tries. */
#endif
#define TELEMETRY_REFRESH_INTERVAL 0.5
/* Simple repeatable random numbers. */
static uint64_t rng_state = 0x853c49e6748fea9bULL;
@@ -220,25 +222,17 @@ struct background_metrics {
int samples, available;
};
#define MAX_TELEMETRY_SAMPLES 1800
#define MAX_TELEMETRY_PHASES 44
struct telemetry_sample {
uint64_t elapsed_ms;
double temperature_c, clock_mhz;
};
struct telemetry_phase {
uint64_t elapsed_ms;
const char *suite, *mode;
int workload_index;
};
struct telemetry_monitor {
struct telemetry_sample samples[MAX_TELEMETRY_SAMPLES];
size_t count;
struct telemetry_phase phases[MAX_TELEMETRY_PHASES];
size_t phase_count;
double started;
volatile int stop;
#if defined(_WIN32)
@@ -248,19 +242,6 @@ struct telemetry_monitor {
#endif
};
static void record_telemetry_phase(struct telemetry_monitor *monitor,
const char *suite, int workload_index,
const char *mode)
{
struct telemetry_phase *phase;
if (monitor->phase_count >= MAX_TELEMETRY_PHASES) return;
phase = &monitor->phases[monitor->phase_count++];
phase->elapsed_ms = (uint64_t)((now_seconds() - monitor->started) * 1000.0);
phase->suite = suite;
phase->workload_index = workload_index;
phase->mode = mode;
}
static int read_number_file(const char *path, double *value)
{
FILE *f = fopen(path, "r");
@@ -420,7 +401,7 @@ static void *telemetry_entry(void *arg)
double next = monitor->started;
while (!monitor->stop) {
double current = now_seconds();
if (current >= next) { record_telemetry_sample(monitor); next += 0.25; }
if (current >= next) { record_telemetry_sample(monitor); next += TELEMETRY_REFRESH_INTERVAL; }
telemetry_sleep();
}
record_telemetry_sample(monitor);
@@ -1063,9 +1044,7 @@ int fossbench_run(int verbose, int upload_mode, int system_check)
fflush(stdout);
/* Run every test with all cores and one core. */
record_telemetry_phase(&telemetry, "asm", (int)i, "multicore");
raw_multi[i] = run_test(&tests[i], (int)g_ncores);
record_telemetry_phase(&telemetry, "asm", (int)i, "singlecore");
raw_single[i] = run_test(&tests[i], 1);
printf(" %12.1f %-11s %7.2fs\n",
@@ -1086,9 +1065,7 @@ int fossbench_run(int verbose, int upload_mode, int system_check)
for (i = 0; i < NTESTS; i++) {
printf(" %-24s", tests[i].name);
fflush(stdout);
record_telemetry_phase(&telemetry, "c", (int)i, "multicore");
real_multi[i] = run_test(&tests[i], (int)g_ncores);
record_telemetry_phase(&telemetry, "c", (int)i, "singlecore");
real_single[i] = run_test(&tests[i], 1);
printf(" %12.1f %-11s %7.2fs\n",
display_metric(&tests[i], &real_multi[i]), tests[i].unit,
src/app/upload.c
-15
View File
@@ -246,21 +246,6 @@ static int upload_results(const struct system_info *info,
used += (size_t)n;
}
}
n = snprintf(payload + used, sizeof payload - used, "],\"telemetry_phases\":[");
if (n < 0 || (size_t)n >= sizeof payload - used) return 0;
used += (size_t)n;
{
size_t i;
for (i = 0; i < telemetry->phase_count; i++) {
const struct telemetry_phase *phase = &telemetry->phases[i];
n = snprintf(payload + used, sizeof payload - used,
"%s{\"elapsed_ms\":%llu,\"suite\":\"%s\",\"workload_index\":%d,\"mode\":\"%s\"}",
i ? "," : "", (unsigned long long)phase->elapsed_ms,
phase->suite, phase->workload_index, phase->mode);
if (n < 0 || (size_t)n >= sizeof payload - used) return 0;
used += (size_t)n;
}
}
if (used + 4 >= sizeof payload) return 0;
memcpy(payload + used, "]}}", 4);
payload_len = (int)(used + 3);