Fix refactor latency regression for VK_NV_LowLatency2 by checking if work has already completed

1 files changed, 17 insertions, 10 deletions

diff --git a/src/strategies/low_latency2/swapchain_monitor.cc b/src/strategies/low_latency2/swapchain_monitor.cc
index a70fa6c..7442eec 100644
--- a/src/strategies/low_latency2/swapchain_monitor.cc
+++ b/src/strategies/low_latency2/swapchain_monitor.cc
@@ -35,33 +35,33 @@ void SwapchainMonitor::do_monitor(const std::stop_token stoken) {
     for (;;) {
         auto lock = std::unique_lock{this->mutex};
         this->cv.wait(lock, stoken,
-                      [&]() { return this->semaphore_spans.has_value(); });
+                      [&]() { return !this->pending_signals.empty(); });
 
         // Stop only if we're stopped and we have nothing to signal.
-        if (stoken.stop_requested() && !this->semaphore_spans.has_value()) {
+        if (stoken.stop_requested() && this->pending_signals.empty()) {
             break;
         }
 
         // Grab the most recent semaphore. When work completes, signal it.
-        const auto semaphore_span = std::move(*this->semaphore_spans);
-        this->semaphore_spans.reset();
+        const auto pending_signal = std::move(this->pending_signals.front());
+        this->pending_signals.pop_front();
 
         // If we're stopping, signal the semaphore and don't worry about work
         // actually completing.
         if (stoken.stop_requested()) {
-            semaphore_span.wakeup_semaphore.signal(this->device);
+            pending_signal.wakeup_semaphore.signal(this->device);
             break;
         }
 
         // Unlock, wait for work to finish, lock again.
         lock.unlock();
-        for (const auto& frame_span : semaphore_span.frame_spans) {
+        for (const auto& frame_span : pending_signal.frame_spans) {
             if (frame_span) {
                 frame_span->await_completed();
             }
         }
-
         lock.lock();
+
         using namespace std::chrono;
         if (this->present_delay != 0us) {
             const auto last_time = this->last_signal_time;
@@ -75,7 +75,7 @@ void SwapchainMonitor::do_monitor(const std::stop_token stoken) {
         }
         lock.unlock();
 
-        semaphore_span.wakeup_semaphore.signal(this->device);
+        pending_signal.wakeup_semaphore.signal(this->device);
     }
 }
 
@@ -94,12 +94,19 @@ void SwapchainMonitor::notify_semaphore(const VkSemaphore& timeline_semaphore,
     }
 
     // Signal immediately if we have no outstanding work.
-    if (this->pending_frame_spans.empty()) {
+    if (std::ranges::all_of(this->pending_frame_spans,
+                            [](const auto& frame_span) {
+                                if (!frame_span) {
+                                    return true;
+                                }
+                                return frame_span->has_completed();
+                            })) {
         wakeup_semaphore.signal(this->device);
+        this->pending_signals.clear();
         return;
     }
 
-    this->semaphore_spans.emplace(SemaphoreSpans{
+    this->pending_signals.emplace_back(PendingSignal{
         .wakeup_semaphore = wakeup_semaphore,
         .frame_spans = std::move(this->pending_frame_spans),
     });