add new test start variant

tty_protocol_writer.cpp

@@ -77,6 +77,7 @@ namespace {
 
 constexpr std::size_t kFrameWordCount = 4U;
 constexpr std::size_t kFrameByteCount = kFrameWordCount * sizeof(uint16_t);
+constexpr std::size_t kWriteBatchFrames = 256U;
 
 using EncodedFrame = std::array<std::uint8_t, kFrameByteCount>;
 
@@ -377,7 +378,8 @@ void TtyProtocolWriter::enqueue_frame(uint16_t word0, uint16_t word1, uint16_t w
 
 void TtyProtocolWriter::worker_loop() {
     for (;;) {
-        EncodedFrame frame {};
+        std::array<std::uint8_t, kWriteBatchFrames * kFrameByteCount> write_batch;
+        std::size_t batch_count = 0;
         {
             std::unique_lock<std::mutex> lock(impl_->mutex);
             impl_->data_ready_cv.wait(lock, [this]() {
@@ -388,13 +390,17 @@ void TtyProtocolWriter::worker_loop() {
                 return;
             }
 
-            frame = impl_->ring[impl_->head];
-            impl_->head = (impl_->head + 1U) % impl_->capacity_frames;
-            --impl_->size;
+            batch_count = std::min<std::size_t>(impl_->size, kWriteBatchFrames);
+            for (std::size_t i = 0; i < batch_count; ++i) {
+                const EncodedFrame& frame = impl_->ring[impl_->head];
+                std::memcpy(write_batch.data() + (i * kFrameByteCount), frame.data(), kFrameByteCount);
+                impl_->head = (impl_->head + 1U) % impl_->capacity_frames;
+                --impl_->size;
+            }
         }
 
-        const std::uint8_t* bytes = frame.data();
-        std::size_t remaining = frame.size();
+        const std::uint8_t* bytes = write_batch.data();
+        std::size_t remaining = batch_count * kFrameByteCount;
         while (remaining != 0U) {
             const ssize_t written = ::write(impl_->fd, bytes, remaining);
             if (written < 0) {
@@ -436,7 +442,7 @@ void TtyProtocolWriter::worker_loop() {
 
         {
             std::lock_guard<std::mutex> lock(impl_->mutex);
-            ++impl_->stats.frames_written;
+            impl_->stats.frames_written += static_cast<std::uint64_t>(batch_count);
         }
     }
 }