Before we had this result in our frame timings (with the after/before
counters printed):
0x0000000fffa65090 0x0000000ffea7f9a0
frame: 99 16.6684 16.4952 0.
0195919 0
0x0000000000a540a0 0x0000000fffa65090
frame: 100 1.84467e+13 1.84467e+13 1.7174e-14 0
0x0000000001a2fd30 0x0000000000a540a0
frame: 101 16.6289 16.4461 0.
0216595 0
And now we get:
0x0000000fff3ab690 0x0000000ffe3c4f10
frame: 2387 16.6726 16.609 0.
0173506 0
0x000000000038b420 0x0000000fff3ab690
frame: 2388 16.6455 16.5858 0.
0169653 0
0x000000000137b4c0 0x000000000038b420
frame: 2389 16.7118 16.6509 0.
0168314 0
struct timespec cpu_time_ts;
};
struct timespec cpu_time_ts;
};
+/* Return (a - b) while accounting for the fact that between a and b,
+ * the counter may have wrapped around (with a maximum number of bits
+ * in the counter of GL_QUERY_COUNTER_BITS). */
+static uint64_t
+subtract_timestamp (uint64_t a, uint64_t b)
+{
+ GLint timestamp_bits;
+
+ glGetQueryiv (GL_TIMESTAMP, GL_QUERY_COUNTER_BITS, ×tamp_bits);
+
+ /* Note: "<<" isn't defined for the number of bits in the
+ * type, and the compiler will punish you.
+ */
+ if (timestamp_bits == 64)
+ return a - b;
+
+ if (b > a)
+ return (1ull << timestamp_bits) + a - b;
+ else
+ return a - b;
+}
+
metrics_t *
metrics_create (metrics_info_t *info)
{
metrics_t *
metrics_create (metrics_info_t *info)
{
printf ("# frame: Frame_Number Frame_Time_milliseconds Frame_latency_milliseconds CPU_load GPU_load\n");
} else {
/* Subtract previous frame's times to get frame times. */
printf ("# frame: Frame_Number Frame_Time_milliseconds Frame_latency_milliseconds CPU_load GPU_load\n");
} else {
/* Subtract previous frame's times to get frame times. */
- frame_time_ns = swap_end_timestamp - metrics->previous_swap_end_timestamp;
+ frame_time_ns = subtract_timestamp (swap_end_timestamp,
+ metrics->previous_swap_end_timestamp);
- latency_ns = swap_end_timestamp - metrics->swap_begin_timestamp;
+ latency_ns = subtract_timestamp (swap_end_timestamp,
+ metrics->swap_begin_timestamp);
cpu_time = TIMESPEC_DIFF (metrics->previous_cpu_time_ts, metrics->cpu_time_ts);
cpu_time = TIMESPEC_DIFF (metrics->previous_cpu_time_ts, metrics->cpu_time_ts);