import upstream maccel baseline

bench/evinputlag.c

@@ -0,0 +1,69 @@
+#include <fcntl.h>
+#include <linux/input.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define MOUSE_DEVICE "/dev/input/event7"
+
+static __suseconds_t to_us(struct timeval time) {
+  return time.tv_sec * 1000000L + time.tv_usec;
+}
+
+#define EVENT_TIME_PAIR_CNT 1000 * 3
+
+/**
+ * NOTE: This benchmark depends on temporarily setting
+ * maccel_filter from input_handler.h to inject ktime_t diff (in us)
+ * between when the original event was received and the modified event was
+ * reported, as the value of the REL_Z REL_ABS event. So we can measure the
+ * extra lag from the input_handler. Assuming REL_Z, REL_ABS are only produced
+ * as carriers of the extra lag measurement.
+ *
+ */
+
+int main(void) {
+  int fd_source = open(MOUSE_DEVICE, O_RDONLY);
+  if (fd_source < 0) {
+    perror("Failed to open device");
+    return 1;
+  }
+
+  __suseconds_t times[EVENT_TIME_PAIR_CNT] = {0};
+  int tidx = 0;
+
+  // Main loop to read, modify, and write events
+  struct input_event ev;
+  while (tidx < EVENT_TIME_PAIR_CNT && read(fd_source, &ev, sizeof(ev)) > 0) {
+    struct timeval now;
+    gettimeofday(&now, NULL);
+
+    if (ev.type == EV_REL && (ev.code == 2 || ev.code == 3)) {
+      /* fprintf(stderr, "EVENT: type %d, code %d, value %d\n", ev.type,
+       * ev.code, */
+      /*         ev.value); */
+      times[tidx++] = to_us(ev.time);
+      times[tidx++] = to_us(now);
+      times[tidx++] = ev.value;
+    }
+  }
+
+  // Cleanup
+  close(fd_source);
+
+  tidx = 0;
+
+  printf("event_time,read_time,naive_diff,extra_lag,diff\n"); // eve'ry is in us
+  while (tidx < EVENT_TIME_PAIR_CNT) {
+    __suseconds_t event_time = times[tidx++];
+    __suseconds_t read_time = times[tidx++];
+    __suseconds_t extra_lag_measured_by_input_handler = times[tidx++];
+
+    __suseconds_t diff = read_time - event_time;
+    printf("%lu,%lu,%lu,%lu,%lu\n", event_time, read_time, diff,
+           extra_lag_measured_by_input_handler,
+           diff + extra_lag_measured_by_input_handler);
+  }
+
+  return 0;
+}