import upstream maccel baseline

bench/.gitignore

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+*.o
+bin
+venv

bench/Makefile

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+bench_driver: build
+	@bin/evdriverlag
+
+bench_handler: build
+	@bin/evinputlag
+
+build: evdriverlag.c evinputlag.c
+	@mkdir -p bin
+	@cc evdriverlag.c -o bin/evdriverlag
+	@cc evinputlag.c -o bin/evinputlag
+
+clean:
+	rm *.o

bench/evdriverlag.c

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+#include <fcntl.h>
+#include <linux/input.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define MOUSE_DEVICE "/dev/input/event2"
+
+static __suseconds_t to_us(struct timeval time) {
+  return time.tv_sec * 1000000L + time.tv_usec;
+}
+
+#define EVENT_TIME_PAIR_CNT 1000 * 2
+
+int main(void) {
+  // Open the source device
+  int fd_source = open(MOUSE_DEVICE, O_RDONLY);
+  if (fd_source < 0) {
+    perror("Failed to open source 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);
+
+    times[tidx++] = to_us(ev.time);
+    times[tidx++] = to_us(now);
+  }
+
+  // Cleanup
+  close(fd_source);
+
+  tidx = 0;
+
+  printf("event_time,read_time,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 diff =  ; */
+
+    /* printf("event time: %luus, read time: %luus\n", event_time, read_time);
+     */
+    /* printf("time diff: %luus\n", read_time - event_time); */
+    printf("%lu,%lu,%lu\n", event_time, read_time, read_time - event_time);
+  }
+
+  return 0;
+}

bench/evinputlag.c

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+#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;
+}

bench/plot.py

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+import matplotlib.pyplot as plt
+import numpy as np
+import pandas as pd
+
+control_data = pd.read_csv("control.csv")
+new_data = pd.read_csv("input_handler.csv")
+
+fig, ax = plt.subplots()
+
+ax.plot(np.arange(1000), control_data["diff"], 'b',
+        label=f"Hid-generic (mean = {control_data["diff"].mean()}us)")
+
+ax.plot(np.arange(1000), new_data["diff"], 'g',
+        label=f"New driver  (mean = {new_data["diff"].mean()}us)")
+
+plt.ylabel('lag (us)')
+plt.xlabel('reads')
+
+legend = ax.legend(loc='upper center', fontsize='x-large')
+
+plt.show()
+
+""" Some extra data points out of curiosity """
+
+virtual_minus_source = new_data["virtual_event_time"] - new_data["event_time"]
+print("average lag between source and virtual device:",
+      virtual_minus_source.mean())
+
+new_data["read_minus_virtual"] = new_data["read_time"] - \
+    new_data["virtual_event_time"]
+print("average lag between virtual device and read:",
+      new_data["read_minus_virtual"].mean())

bench/reqs.txt

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+contourpy==1.2.1
+cycler==0.12.1
+fonttools==4.53.1
+kiwisolver==1.4.5
+matplotlib==3.9.1.post1
+numpy==2.0.1
+packaging==24.1
+pillow==10.4.0
+pyparsing==3.1.2
+python-dateutil==2.9.0.post0
+six==1.16.0