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Use a single lane per priority level (#20791)
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(Except transitions and retries.)

The idea is that the only priorities that benefit from multiple parallel
updates are the ones that might suspend: transitions and retries. All
other priorities, including the ones that are interruptible like
Continuous and Idle, don't need multiple lanes because it's better to
batch everything together.
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@acdlite
acdlite authored Feb 11, 2021
1 parent b593a6f commit d3d2451
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195 changes: 100 additions & 95 deletions packages/react-reconciler/src/ReactFiberLane.new.js
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Original file line number Diff line number Diff line change
Expand Up @@ -85,38 +85,49 @@ export const SyncLane: Lane = /* */ 0b0000000000000000000
export const SyncBatchedLane: Lane = /* */ 0b0000000000000000000000000000010;

export const InputDiscreteHydrationLane: Lane = /* */ 0b0000000000000000000000000000100;
const InputDiscreteLanes: Lanes = /* */ 0b0000000000000000000000000011000;
const InputDiscreteLane: Lanes = /* */ 0b0000000000000000000000000001000;

const InputContinuousHydrationLane: Lane = /* */ 0b0000000000000000000000000100000;
const InputContinuousLanes: Lanes = /* */ 0b0000000000000000000000011000000;
const InputContinuousLane: Lanes = /* */ 0b0000000000000000000000001000000;

export const DefaultHydrationLane: Lane = /* */ 0b0000000000000000000000100000000;
export const DefaultLanes: Lanes = /* */ 0b0000000000000000000111000000000;
export const DefaultLane: Lanes = /* */ 0b0000000000000000000001000000000;

const TransitionHydrationLane: Lane = /* */ 0b0000000000000000001000000000000;
const TransitionLanes: Lanes = /* */ 0b0000000001111111110000000000000;
const FirstTransitionLane: Lane = /* */ 0b0000000000000000010000000000000;
const TransitionLane1: Lane = /* */ 0b0000000000000000010000000000000;
const TransitionLane2: Lane = /* */ 0b0000000000000000100000000000000;
const TransitionLane3: Lane = /* */ 0b0000000000000001000000000000000;
const TransitionLane4: Lane = /* */ 0b0000000000000010000000000000000;
const TransitionLane5: Lane = /* */ 0b0000000000000100000000000000000;
const TransitionLane6: Lane = /* */ 0b0000000000001000000000000000000;
const TransitionLane7: Lane = /* */ 0b0000000000010000000000000000000;
const TransitionLane8: Lane = /* */ 0b0000000000100000000000000000000;
const TransitionLane9: Lane = /* */ 0b0000000001000000000000000000000;

const RetryLanes: Lanes = /* */ 0b0000011110000000000000000000000;
const RetryLane1: Lane = /* */ 0b0000000010000000000000000000000;
const RetryLane2: Lane = /* */ 0b0000000100000000000000000000000;
const RetryLane3: Lane = /* */ 0b0000001000000000000000000000000;
const RetryLane4: Lane = /* */ 0b0000010000000000000000000000000;

const FirstRetryLane: Lanes = /* */ 0b0000000010000000000000000000000;
export const SomeRetryLane: Lane = FirstRetryLane;
export const SomeRetryLane: Lane = RetryLane1;

export const SelectiveHydrationLane: Lane = /* */ 0b0000100000000000000000000000000;

const NonIdleLanes = /* */ 0b0000111111111111111111111111111;

export const IdleHydrationLane: Lane = /* */ 0b0001000000000000000000000000000;
const IdleLanes: Lanes = /* */ 0b0110000000000000000000000000000;
const IdleLane: Lanes = /* */ 0b0010000000000000000000000000000;

export const OffscreenLane: Lane = /* */ 0b1000000000000000000000000000000;

export const NoTimestamp = -1;

let currentUpdateLanePriority: LanePriority = NoLanePriority;

let nextTransitionLane: Lane = FirstTransitionLane;
let nextRetryLane: Lane = FirstRetryLane;
let nextTransitionLane: Lane = TransitionLane1;
let nextRetryLane: Lane = RetryLane1;

export function getCurrentUpdateLanePriority(): LanePriority {
return currentUpdateLanePriority;
Expand All @@ -131,78 +142,73 @@ export function setCurrentUpdateLanePriority(newLanePriority: LanePriority) {
let return_highestLanePriority: LanePriority = DefaultLanePriority;

function getHighestPriorityLanes(lanes: Lanes | Lane): Lanes {
if ((SyncLane & lanes) !== NoLanes) {
return_highestLanePriority = SyncLanePriority;
return SyncLane;
}
if ((SyncBatchedLane & lanes) !== NoLanes) {
return_highestLanePriority = SyncBatchedLanePriority;
return SyncBatchedLane;
}
if ((InputDiscreteHydrationLane & lanes) !== NoLanes) {
return_highestLanePriority = InputDiscreteHydrationLanePriority;
return InputDiscreteHydrationLane;
}
const inputDiscreteLanes = InputDiscreteLanes & lanes;
if (inputDiscreteLanes !== NoLanes) {
return_highestLanePriority = InputDiscreteLanePriority;
return inputDiscreteLanes;
}
if ((lanes & InputContinuousHydrationLane) !== NoLanes) {
return_highestLanePriority = InputContinuousHydrationLanePriority;
return InputContinuousHydrationLane;
}
const inputContinuousLanes = InputContinuousLanes & lanes;
if (inputContinuousLanes !== NoLanes) {
return_highestLanePriority = InputContinuousLanePriority;
return inputContinuousLanes;
}
if ((lanes & DefaultHydrationLane) !== NoLanes) {
return_highestLanePriority = DefaultHydrationLanePriority;
return DefaultHydrationLane;
}
const defaultLanes = DefaultLanes & lanes;
if (defaultLanes !== NoLanes) {
return_highestLanePriority = DefaultLanePriority;
return defaultLanes;
}
if ((lanes & TransitionHydrationLane) !== NoLanes) {
return_highestLanePriority = TransitionHydrationPriority;
return TransitionHydrationLane;
}
const transitionLanes = TransitionLanes & lanes;
if (transitionLanes !== NoLanes) {
return_highestLanePriority = TransitionPriority;
return transitionLanes;
}
const retryLanes = RetryLanes & lanes;
if (retryLanes !== NoLanes) {
return_highestLanePriority = RetryLanePriority;
return retryLanes;
}
if (lanes & SelectiveHydrationLane) {
return_highestLanePriority = SelectiveHydrationLanePriority;
return SelectiveHydrationLane;
}
if ((lanes & IdleHydrationLane) !== NoLanes) {
return_highestLanePriority = IdleHydrationLanePriority;
return IdleHydrationLane;
}
const idleLanes = IdleLanes & lanes;
if (idleLanes !== NoLanes) {
return_highestLanePriority = IdleLanePriority;
return idleLanes;
}
if ((OffscreenLane & lanes) !== NoLanes) {
return_highestLanePriority = OffscreenLanePriority;
return OffscreenLane;
}
if (__DEV__) {
console.error('Should have found matching lanes. This is a bug in React.');
switch (getHighestPriorityLane(lanes)) {
case SyncLane:
return_highestLanePriority = SyncLanePriority;
return SyncLane;
case SyncBatchedLane:
return_highestLanePriority = SyncBatchedLanePriority;
return SyncBatchedLane;
case InputDiscreteHydrationLane:
return_highestLanePriority = InputDiscreteHydrationLanePriority;
return InputDiscreteHydrationLane;
case InputDiscreteLane:
return_highestLanePriority = InputDiscreteLanePriority;
return InputDiscreteLane;
case InputContinuousHydrationLane:
return_highestLanePriority = InputContinuousHydrationLanePriority;
return InputContinuousHydrationLane;
case InputContinuousLane:
return_highestLanePriority = InputContinuousLanePriority;
return InputContinuousLane;
case DefaultHydrationLane:
return_highestLanePriority = DefaultHydrationLanePriority;
return DefaultHydrationLane;
case DefaultLane:
return_highestLanePriority = DefaultLanePriority;
return DefaultLane;
case TransitionHydrationLane:
return_highestLanePriority = TransitionHydrationPriority;
return TransitionHydrationLane;
case TransitionLane1:
case TransitionLane2:
case TransitionLane3:
case TransitionLane4:
case TransitionLane5:
case TransitionLane6:
case TransitionLane7:
case TransitionLane8:
case TransitionLane9:
return_highestLanePriority = TransitionPriority;
return lanes & TransitionLanes;
case RetryLane1:
case RetryLane2:
case RetryLane3:
case RetryLane4:
return_highestLanePriority = RetryLanePriority;
return lanes & RetryLanes;
case SelectiveHydrationLane:
return_highestLanePriority = SelectiveHydrationLanePriority;
return SelectiveHydrationLane;
case IdleHydrationLane:
return_highestLanePriority = IdleHydrationLanePriority;
return IdleHydrationLane;
case IdleLane:
return_highestLanePriority = IdleLanePriority;
return IdleLane;
case OffscreenLane:
return_highestLanePriority = OffscreenLanePriority;
return OffscreenLane;
default:
if (__DEV__) {
console.error(
'Should have found matching lanes. This is a bug in React.',
);
}
// This shouldn't be reachable, but as a fallback, return the entire bitmask.
return_highestLanePriority = DefaultLanePriority;
return lanes;
}
// This shouldn't be reachable, but as a fallback, return the entire bitmask.
return_highestLanePriority = DefaultLanePriority;
return lanes;
}

export function schedulerPriorityToLanePriority(
Expand Down Expand Up @@ -516,20 +522,17 @@ export function findUpdateLane(lanePriority: LanePriority): Lane {
return SyncLane;
case SyncBatchedLanePriority:
return SyncBatchedLane;
case InputDiscreteLanePriority: {
return pickArbitraryLane(InputDiscreteLanes);
}
case InputContinuousLanePriority: {
return pickArbitraryLane(InputContinuousLanes);
}
case DefaultLanePriority: {
return pickArbitraryLane(DefaultLanes);
}
case InputDiscreteLanePriority:
return InputDiscreteLane;
case InputContinuousLanePriority:
return InputContinuousLane;
case DefaultLanePriority:
return DefaultLane;
case TransitionPriority: // Should be handled by findTransitionLane instead
case RetryLanePriority: // Should be handled by findRetryLane instead
break;
case IdleLanePriority:
return pickArbitraryLane(IdleLanes);
return IdleLane;
default:
// The remaining priorities are not valid for updates
break;
Expand All @@ -549,7 +552,7 @@ export function claimNextTransitionLane(): Lane {
const lane = nextTransitionLane;
nextTransitionLane <<= 1;
if ((nextTransitionLane & TransitionLanes) === 0) {
nextTransitionLane = FirstTransitionLane;
nextTransitionLane = TransitionLane1;
}
return lane;
}
Expand All @@ -558,7 +561,7 @@ export function claimNextRetryLane(): Lane {
const lane = nextRetryLane;
nextRetryLane <<= 1;
if ((nextRetryLane & RetryLanes) === 0) {
nextRetryLane = FirstRetryLane;
nextRetryLane = RetryLane1;
}
return lane;
}
Expand Down Expand Up @@ -650,7 +653,7 @@ export function markRootUpdated(
// We don't do this if the incoming update is idle, because we never process
// idle updates until after all the regular updates have finished; there's no
// way it could unblock a transition.
if ((updateLane & IdleLanes) === NoLanes) {
if (updateLane !== IdleLane) {
root.suspendedLanes = NoLanes;
root.pingedLanes = NoLanes;
}
Expand Down Expand Up @@ -692,11 +695,13 @@ export function markRootExpired(root: FiberRoot, expiredLanes: Lanes) {
}

export function markDiscreteUpdatesExpired(root: FiberRoot) {
root.expiredLanes |= InputDiscreteLanes & root.pendingLanes;
if (root.pendingLanes & InputDiscreteLane) {
root.expiredLanes |= InputDiscreteLane;
}
}

export function hasDiscreteLanes(lanes: Lanes) {
return (lanes & InputDiscreteLanes) !== NoLanes;
return (lanes & InputDiscreteLane) !== NoLanes;
}

export function markRootMutableRead(root: FiberRoot, updateLane: Lane) {
Expand Down
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