Optimize Pdu prev_events and auth_events containers.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/matrix/pdu.rs

@@ -17,6 +17,7 @@ use ruma::{
 };
 use serde::{Deserialize, Serialize};
 use serde_json::value::RawValue as RawJsonValue;
+use smallvec::SmallVec;
 
 pub use self::{
 	Count as PduCount, Id as PduId, Pdu as PduEvent, RawId as RawPduId,
@@ -32,39 +33,39 @@ use crate::Result;
 /// Persistent Data Unit (Event)
 #[derive(Clone, Deserialize, Serialize, Debug)]
 pub struct Pdu {
+	#[serde(rename = "type")]
+	pub kind: TimelineEventType,
+
+	pub content: Box<RawJsonValue>,
+
 	pub event_id: OwnedEventId,
 
 	pub room_id: OwnedRoomId,
 
 	pub sender: OwnedUserId,
 
-	#[serde(skip_serializing_if = "Option::is_none")]
-	pub origin: Option<OwnedServerName>,
-
-	pub origin_server_ts: UInt,
-
-	#[serde(rename = "type")]
-	pub kind: TimelineEventType,
-
-	pub content: Box<RawJsonValue>,
-
 	#[serde(skip_serializing_if = "Option::is_none")]
 	pub state_key: Option<StateKey>,
 
-	pub prev_events: Vec<OwnedEventId>,
-
-	pub depth: UInt,
-
-	pub auth_events: Vec<OwnedEventId>,
-
 	#[serde(skip_serializing_if = "Option::is_none")]
 	pub redacts: Option<OwnedEventId>,
 
-	#[serde(default, skip_serializing_if = "Option::is_none")]
-	pub unsigned: Option<Box<RawJsonValue>>,
+	pub prev_events: PrevEvents,
+
+	pub auth_events: AuthEvents,
+
+	pub origin_server_ts: UInt,
+
+	pub depth: UInt,
 
 	pub hashes: EventHash,
 
+	#[serde(skip_serializing_if = "Option::is_none")]
+	pub origin: Option<OwnedServerName>,
+
+	#[serde(default, skip_serializing_if = "Option::is_none")]
+	pub unsigned: Option<Box<RawJsonValue>>,
+
 	// BTreeMap<Box<ServerName>, BTreeMap<ServerSigningKeyId, String>>
 	#[serde(default, skip_serializing_if = "Option::is_none")]
 	pub signatures: Option<Box<RawJsonValue>>,
@@ -75,6 +76,16 @@ pub struct Pdu {
 	pub rejected: bool,
 }
 
+/// Tuned prev_events vector. Most events have one prev_event. Many events have
+/// more but allocations for all of those cases still beats allocations for all
+/// cases.
+pub type PrevEvents = SmallVec<[OwnedEventId; 1]>;
+
+/// Tuned auth_events vector. Average events have three auth events. It is
+/// debatable whether this could be an ArrayVec but the realistic upper-bound is
+/// too high and non-deterministic in the era of restricted-type rooms.
+pub type AuthEvents = SmallVec<[OwnedEventId; 3]>;
+
 /// The [maximum size allowed] for a PDU.
 /// [maximum size allowed]: https://spec.matrix.org/latest/client-server-api/#size-limits
 pub const MAX_PDU_BYTES: usize = 65_535;

src/core/matrix/state_res/benches.rs

@@ -433,13 +433,13 @@ where
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 
 	let prev_events = prev_events
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 
 	let state_key = state_key.map(ToOwned::to_owned);
 	PduEvent {

src/core/matrix/state_res/event_auth/tests.rs

@@ -669,8 +669,8 @@ async fn auth_event_in_different_room() {
 		content: to_raw_json_value(&json!({ "users": { alice(): 100 } })).unwrap(),
 		redacts: None,
 		unsigned: None,
-		auth_events: vec![event_id("CREATE"), event_id("IMA")],
-		prev_events: vec![event_id("IMA")],
+		auth_events: vec![event_id("CREATE"), event_id("IMA")].into(),
+		prev_events: vec![event_id("IMA")].into(),
 		depth: uint!(0),
 		hashes: EventHash::default(),
 		signatures: None,
@@ -807,8 +807,8 @@ async fn rejected_auth_event() {
 		content: to_raw_json_value(&json!({ "users": { alice(): 100 } })).unwrap(),
 		redacts: None,
 		unsigned: None,
-		auth_events: vec![event_id("CREATE"), event_id("IMA")],
-		prev_events: vec![event_id("IMA")],
+		auth_events: vec![event_id("CREATE"), event_id("IMA")].into(),
+		prev_events: vec![event_id("IMA")].into(),
 		depth: uint!(0),
 		hashes: EventHash::default(),
 		signatures: None,
@@ -893,12 +893,13 @@ async fn event_without_room_id() {
 		content: to_raw_json_value(&RoomMessageEventContent::text_plain("Hi!")).unwrap(),
 		redacts: None,
 		unsigned: None,
-		auth_events: vec![
+		auth_events: [
 			owned_event_id!("$CREATE"),
 			owned_event_id!("$IMA"),
 			owned_event_id!("$IPOWER"),
-		],
-		prev_events: vec![owned_event_id!("$IPOWER")],
+		]
+		.into(),
+		prev_events: [owned_event_id!("$IPOWER")].into(),
 		depth: uint!(0),
 		hashes: EventHash::default(),
 		signatures: None,

src/core/matrix/state_res/resolve/tests.rs

@@ -163,7 +163,7 @@ async fn topic_basic() {
 			.finish(),
 	);
 
-	let events = &[
+	let events = vec![
 		to_init_pdu_event(
 			"T1",
 			alice(),
@@ -219,7 +219,7 @@ async fn topic_basic() {
 		.map(event_id)
 		.collect::<Vec<_>>();
 
-	do_check(events, edges, expected_state_ids).await;
+	do_check(&events, edges, expected_state_ids).await;
 }
 
 #[tokio::test]

src/core/matrix/state_res/test_utils.rs

@@ -428,13 +428,13 @@ pub(super) fn to_init_pdu_event(
 	content: Box<RawJsonValue>,
 ) -> PduEvent {
 	let ts = SERVER_TIMESTAMP.fetch_add(1, SeqCst);
+	let state_key = state_key.map(ToOwned::to_owned);
 	let id = if id.contains('$') {
 		id.to_owned()
 	} else {
 		format!("${id}:foo")
 	};
 
-	let state_key = state_key.map(ToOwned::to_owned);
 	PduEvent {
 		event_id: id.try_into().unwrap(),
 		room_id: room_id().to_owned(),
@@ -446,8 +446,8 @@ pub(super) fn to_init_pdu_event(
 		content,
 		redacts: None,
 		unsigned: None,
-		auth_events: vec![],
-		prev_events: vec![],
+		auth_events: Default::default(),
+		prev_events: Default::default(),
 		depth: uint!(0),
 		hashes: EventHash::default(),
 		signatures: None,
@@ -468,6 +468,7 @@ where
 	S: AsRef<str>,
 {
 	let ts = SERVER_TIMESTAMP.fetch_add(1, SeqCst);
+	let state_key = state_key.map(ToOwned::to_owned);
 	let id = if id.contains('$') {
 		id.to_owned()
 	} else {
@@ -477,14 +478,13 @@ where
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 	let prev_events = prev_events
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 
-	let state_key = state_key.map(ToOwned::to_owned);
 	PduEvent {
 		event_id: id.try_into().unwrap(),
 		room_id: room_id().to_owned(),
@@ -528,18 +528,18 @@ where
 	}
 
 	let ts = SERVER_TIMESTAMP.fetch_add(1, SeqCst);
+	let state_key = state_key.map(ToOwned::to_owned);
 	let auth_events = auth_events
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 	let prev_events = prev_events
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 
-	let state_key = state_key.map(ToOwned::to_owned);
 	PduEvent {
 		event_id: event_id(id),
 		room_id: hydra_room_id().to_owned(),
@@ -581,12 +581,12 @@ where
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 	let prev_events = prev_events
 		.iter()
 		.map(AsRef::as_ref)
 		.map(event_id)
-		.collect::<Vec<_>>();
+		.collect();
 
 	PduEvent {
 		event_id: id.try_into().unwrap(),
@@ -636,8 +636,8 @@ pub(super) fn room_create_hydra_pdu_event(
 		content,
 		redacts: None,
 		unsigned: None,
-		auth_events: vec![],
-		prev_events: vec![],
+		auth_events: Default::default(),
+		prev_events: Default::default(),
 		depth: uint!(0),
 		hashes: EventHash::default(),
 		signatures: None,