perf_self_monitor: Start working on stats

1 files changed, 45 insertions, 12 deletions

diff --git a/tight_loop/perf_self_monitor.c b/tight_loop/perf_self_monitor.c
index f3de608..33c2be2 100644
--- a/tight_loop/perf_self_monitor.c
+++ b/tight_loop/perf_self_monitor.c
@@ -6,6 +6,7 @@
 #include <string.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <err.h>
 
@@ -151,6 +152,49 @@ bool psm_atomic_sample_empty(uint64_t *count,
 	return psm_atomic_elapsed(count, &duration, ctr);
 }
 
+bool psm_atomic_sample_enosys(uint64_t *count,
+			      const struct psm_counter *ctr, void *opaque)
+{
+	struct psm_atomic duration = psm_atomic_start(ctr);
+	unsigned long rax;
+	rax = 0xbfffffff;
+	asm volatile ("syscall" : "+a" (rax) : : "rcx", "r11");
+	return psm_atomic_elapsed(count, &duration, ctr);
+}
+
+static int compare_ui64(const void *a_void, const void *b_void)
+{
+	const uint64_t a = *(uint64_t*)a_void;
+	const uint64_t b = *(uint64_t*)b_void;
+	if (a < b)
+		return -1;
+	else if (a > b)
+		return 1;
+	else
+		return 0;
+}
+
+uint64_t psm_integer_quantile(const struct psm_counter *ctr, psm_sample_fn fn,
+			      void *opaque, size_t q, size_t n)
+{
+	if (q >= n)
+		abort();
+
+	uint64_t *array = calloc(sizeof(uint64_t), n);
+	for (size_t i = 0; i < n; ) {
+		uint64_t sample;
+		if (!fn(&sample, ctr, opaque))
+			continue;
+		array[i++] = sample;
+	}
+
+	qsort(array, n, sizeof(uint64_t), compare_ui64);
+
+	uint64_t ret = array[q];
+	free(array);
+	return ret;
+}
+
 void psm_settle(const struct psm_counter *ctr, psm_sample_fn fn, void *opaque)
 {
 	uint64_t val = UINT64_MAX;
@@ -184,18 +228,7 @@ int main()
 	psm_settle(ctr, psm_atomic_sample_empty, NULL);
 
 	for (int i = 0; i < 20; i++) {
-		struct psm_atomic duration = psm_atomic_start(ctr);
-		unsigned long rax;
-		rax = 0xbfffffff;
-		asm volatile ("syscall" : "+a" (rax) : : "rcx", "r11");
-		rax = 0xbfffffff;
-		asm volatile ("syscall" : "+a" (rax) : : "rcx", "r11");
-		uint64_t cycles;
-		bool ok = psm_atomic_elapsed(&cycles, &duration, ctr);
-		if (ok)
-			printf("%d: %lld\n", i, (unsigned long long)cycles);
-		else
-			printf("sadness\n");
+		printf("%llu\n", (unsigned long long)psm_integer_quantile(ctr, psm_atomic_sample_enosys, NULL, 0, 500));
 	}
 
 	psm_counter_destroy(ctr);