Driver, Input: Performance & Benchmarks (#27)

* Driver Benchmarks

Benchmarks driver use cases for single packet send,
multiple packet send, float vs opus, and the cost of
head-of-queue track removal.

Mix costs for large packet counts are also included.

This is a prelude to the optimisations discussed in
#21.

* Typo in benchmark

* Place Opus packet directly into packet buffer

Cleans up some other logic surrounding this, too. Gets a 16.9% perf improvement on opus packet passthrough (sub 5us here).

* Better track removal

In theory this should be faster, but it aint. Keeping in case
reducing struct sizes down the line magically makes this
faster.

* Reduce size of Input, TrackHandle

Metadata is now boxed away. Similarly, TrackHandles are neatly Arc'd to reduce their size to pointer length (and mitigate the impact of copies if we add in more fields).

benches/mixing-task.rs

@@ -0,0 +1,237 @@
+use criterion::{
+    black_box,
+    criterion_group,
+    criterion_main,
+    BatchSize,
+    Bencher,
+    BenchmarkId,
+    Criterion,
+};
+use flume::{Receiver, Sender, TryRecvError};
+use songbird::{
+    constants::*,
+    driver::bench_internals::{mixer::Mixer, task_message::*, CryptoState},
+    input::{cached::Compressed, Input},
+    tracks,
+    Bitrate,
+};
+use tokio::runtime::{Handle, Runtime};
+use xsalsa20poly1305::{aead::NewAead, XSalsa20Poly1305 as Cipher, KEY_SIZE};
+
+// create a dummied task + interconnect.
+// measure perf at varying numbers of sources (binary 1--64) without passthrough support.
+
+fn dummied_mixer(
+    handle: Handle,
+) -> (
+    Mixer,
+    (
+        Receiver<CoreMessage>,
+        Receiver<EventMessage>,
+        Receiver<UdpRxMessage>,
+        Receiver<UdpTxMessage>,
+    ),
+) {
+    let (mix_tx, mix_rx) = flume::unbounded();
+    let (core_tx, core_rx) = flume::unbounded();
+    let (event_tx, event_rx) = flume::unbounded();
+
+    let (udp_sender_tx, udp_sender_rx) = flume::unbounded();
+    let (udp_receiver_tx, udp_receiver_rx) = flume::unbounded();
+
+    let ic = Interconnect {
+        core: core_tx,
+        events: event_tx,
+        mixer: mix_tx,
+    };
+
+    let mut out = Mixer::new(mix_rx, handle, ic, Default::default());
+
+    let fake_conn = MixerConnection {
+        cipher: Cipher::new_varkey(&vec![0u8; KEY_SIZE]).unwrap(),
+        crypto_state: CryptoState::Normal,
+        udp_rx: udp_receiver_tx,
+        udp_tx: udp_sender_tx,
+    };
+
+    out.conn_active = Some(fake_conn);
+
+    out.skip_sleep = true;
+
+    (out, (core_rx, event_rx, udp_receiver_rx, udp_sender_rx))
+}
+
+fn mixer_float(
+    num_tracks: usize,
+    handle: Handle,
+) -> (
+    Mixer,
+    (
+        Receiver<CoreMessage>,
+        Receiver<EventMessage>,
+        Receiver<UdpRxMessage>,
+        Receiver<UdpTxMessage>,
+    ),
+) {
+    let mut out = dummied_mixer(handle);
+
+    let floats = utils::make_sine(10 * STEREO_FRAME_SIZE, true);
+
+    let mut tracks = vec![];
+    for i in 0..num_tracks {
+        let input = Input::float_pcm(true, floats.clone().into());
+        tracks.push(tracks::create_player(input).0.into());
+    }
+
+    out.0.tracks = tracks;
+
+    out
+}
+
+fn mixer_float_drop(
+    num_tracks: usize,
+    handle: Handle,
+) -> (
+    Mixer,
+    (
+        Receiver<CoreMessage>,
+        Receiver<EventMessage>,
+        Receiver<UdpRxMessage>,
+        Receiver<UdpTxMessage>,
+    ),
+) {
+    let mut out = dummied_mixer(handle);
+
+    let mut tracks = vec![];
+    for i in 0..num_tracks {
+        let floats = utils::make_sine((i / 5) * STEREO_FRAME_SIZE, true);
+        let input = Input::float_pcm(true, floats.clone().into());
+        tracks.push(tracks::create_player(input).0.into());
+    }
+
+    out.0.tracks = tracks;
+
+    out
+}
+
+fn mixer_opus(
+    handle: Handle,
+) -> (
+    Mixer,
+    (
+        Receiver<CoreMessage>,
+        Receiver<EventMessage>,
+        Receiver<UdpRxMessage>,
+        Receiver<UdpTxMessage>,
+    ),
+) {
+    // should add a single opus-based track.
+    // make this fully loaded to prevent any perf cost there.
+    let mut out = dummied_mixer(handle);
+
+    let floats = utils::make_sine(6 * STEREO_FRAME_SIZE, true);
+
+    let mut tracks = vec![];
+
+    let mut src = Compressed::new(
+        Input::float_pcm(true, floats.clone().into()),
+        Bitrate::BitsPerSecond(128_000),
+    )
+    .expect("These parameters are well-defined.");
+    src.raw.load_all();
+
+    tracks.push(tracks::create_player(src.into()).0.into());
+
+    out.0.tracks = tracks;
+
+    out
+}
+
+fn no_passthrough(c: &mut Criterion) {
+    let rt = Runtime::new().unwrap();
+
+    let mut group = c.benchmark_group("Float Input (No Passthrough)");
+
+    for shift in 0..=6 {
+        let track_count = 1 << shift;
+
+        group.bench_with_input(
+            BenchmarkId::new("Single Packet", track_count),
+            &track_count,
+            |b, i| {
+                b.iter_batched_ref(
+                    || black_box(mixer_float(*i, rt.handle().clone())),
+                    |input| {
+                        black_box(input.0.cycle());
+                    },
+                    BatchSize::SmallInput,
+                )
+            },
+        );
+        group.bench_with_input(
+            BenchmarkId::new("n=5 Packets", track_count),
+            &track_count,
+            |b, i| {
+                b.iter_batched_ref(
+                    || black_box(mixer_float(*i, rt.handle().clone())),
+                    |input| {
+                        for i in 0..5 {
+                            black_box(input.0.cycle());
+                        }
+                    },
+                    BatchSize::SmallInput,
+                )
+            },
+        );
+    }
+
+    group.finish();
+}
+
+fn passthrough(c: &mut Criterion) {
+    let rt = Runtime::new().unwrap();
+
+    let mut group = c.benchmark_group("Opus Input (Passthrough)");
+
+    group.bench_function("Single Packet", |b| {
+        b.iter_batched_ref(
+            || black_box(mixer_opus(rt.handle().clone())),
+            |input| {
+                black_box(input.0.cycle());
+            },
+            BatchSize::SmallInput,
+        )
+    });
+    group.bench_function("n=5 Packets", |b| {
+        b.iter_batched_ref(
+            || black_box(mixer_opus(rt.handle().clone())),
+            |input| {
+                for i in 0..5 {
+                    black_box(input.0.cycle());
+                }
+            },
+            BatchSize::SmallInput,
+        )
+    });
+
+    group.finish();
+}
+
+fn culling(c: &mut Criterion) {
+    let rt = Runtime::new().unwrap();
+
+    c.bench_function("Worst-case Track Culling (15 tracks, 5 pkts)", |b| {
+        b.iter_batched_ref(
+            || black_box(mixer_float_drop(15, rt.handle().clone())),
+            |input| {
+                for i in 0..5 {
+                    black_box(input.0.cycle());
+                }
+            },
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+criterion_group!(benches, no_passthrough, passthrough, culling);
+criterion_main!(benches);