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main: improve delayed rendering

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We now use two timers for delayed rendering; one _lower_ limit timeout
that is reset each time we receive input from the slave. We never
render *before* this timeout. Since it's reset, this means rendering
may be pushed further into the future.

To prevent this from happening indefinitely, the second timer defines
the _upper_ limit. This timer is only reset after rendering.

Thus, slave input may now increase the rendering delay, but only up to
a certain limit.

The lower limit is as before, 1ms. The upper limit is set to 16ms (the
time between frame updates on a 60HZ output).
This commit is contained in:
Daniel Eklöf 2019-09-20 18:08:15 +02:00
parent aa41c8ceb1
commit 652ff5da92
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GPG key ID: 5BBD4992C116573F
1 changed files with 38 additions and 12 deletions
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50
main.c
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@ -890,7 +890,8 @@ main(int argc, char *const *argv)
} }
bool timeout_is_armed = false; bool timeout_is_armed = false;
int timeout_fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK | TFD_CLOEXEC); int timeout_fd1 = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK | TFD_CLOEXEC);
int timeout_fd2 = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK | TFD_CLOEXEC);
while (true) { while (true) {
struct pollfd fds[] = { struct pollfd fds[] = {
@ -899,7 +900,8 @@ main(int argc, char *const *argv)
{.fd = term.kbd.repeat.fd, .events = POLLIN}, {.fd = term.kbd.repeat.fd, .events = POLLIN},
{.fd = term.flash.fd, .events = POLLIN}, {.fd = term.flash.fd, .events = POLLIN},
{.fd = term.blink.fd, .events = POLLIN}, {.fd = term.blink.fd, .events = POLLIN},
{.fd = timeout_fd, .events = POLLIN}, {.fd = timeout_fd1, .events = POLLIN},
{.fd = timeout_fd2, .events = POLLIN},
}; };
wl_display_flush(term.wl.display); wl_display_flush(term.wl.display);
@ -913,18 +915,30 @@ main(int argc, char *const *argv)
break; break;
} }
if (fds[5].revents & POLLIN) { /* Delayed rendering timers (created when we receive input) */
if (fds[5].revents & POLLIN || fds[6].revents & POLLIN) {
assert(timeout_is_armed); assert(timeout_is_armed);
uint64_t unused; uint64_t unused;
ssize_t ret = read(timeout_fd, &unused, sizeof(unused)); ssize_t ret1 = 0;
ssize_t ret2 = 0;
if (ret < 0 && errno != EAGAIN) if (fds[5].revents & POLLIN)
ret1 = read(timeout_fd1, &unused, sizeof(unused));
if (fds[6].revents & POLLIN)
ret2 = read(timeout_fd2, &unused, sizeof(unused));
if ((ret1 < 0 || ret2 < 0) && errno != EAGAIN)
LOG_ERRNO("failed to read timeout timer"); LOG_ERRNO("failed to read timeout timer");
else if (ret > 0) { else if (ret1 > 0 || ret2 > 0) {
timeout_is_armed = false;
render_refresh(&term); render_refresh(&term);
}
/* Reset timers */
timeout_is_armed = false;
timerfd_settime(timeout_fd1, 0, &(struct itimerspec){.it_value = {0}}, NULL);
timerfd_settime(timeout_fd2, 0, &(struct itimerspec){.it_value = {0}}, NULL);
} else
assert(false);
} }
if (fds[0].revents & POLLIN) { if (fds[0].revents & POLLIN) {
@ -968,6 +982,11 @@ main(int argc, char *const *argv)
* us time to receive the last writes before doing any * us time to receive the last writes before doing any
* actual rendering). * actual rendering).
* *
* We incur this delay *every* time we receive
* input. To ensure we don't delay rendering
* indefinitely, we start a second timer that is only
* reset when we render.
*
* Note that when the client is producing data at a * Note that when the client is producing data at a
* very high pace, we're rate limited by the wayland * very high pace, we're rate limited by the wayland
* compositor anyway. The delay we introduce here only * compositor anyway. The delay we introduce here only
@ -977,9 +996,15 @@ main(int argc, char *const *argv)
* ourselves we just received keyboard input, and in * ourselves we just received keyboard input, and in
* this case *not* delay rendering? * this case *not* delay rendering?
*/ */
if (!timeout_is_armed) { if (term.render.frame_callback == NULL) {
timerfd_settime(timeout_fd, 0, &(struct itimerspec){.it_value = {.tv_nsec = 1000000}}, NULL); /* First timeout - reset each time we receive input. */
timeout_is_armed = true; timerfd_settime(timeout_fd1, 0, &(struct itimerspec){.it_value = {.tv_nsec = 1000000}}, NULL);
/* Second timeout - only reset when we render. Set to one frame (assuming 60HZ) */
if (!timeout_is_armed) {
timerfd_settime(timeout_fd2, 0, &(struct itimerspec){.it_value = {.tv_nsec = 16666666}}, NULL);
timeout_is_armed = true;
}
} }
} }
} }
@ -1053,7 +1078,8 @@ main(int argc, char *const *argv)
} }
} }
close(timeout_fd); close(timeout_fd1);
close(timeout_fd2);
out: out:
mtx_lock(&term.render.workers.lock); mtx_lock(&term.render.workers.lock);