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useMutableSource reduce amount of metadata cached during render
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Brian Vaughn committed Feb 7, 2020
1 parent 48ae0c0 commit 876dd7c
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Showing 5 changed files with 75 additions and 81 deletions.
79 changes: 48 additions & 31 deletions packages/react-reconciler/src/ReactFiberHooks.js
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import type {
} from 'shared/ReactMutableSource';

import ReactSharedInternals from 'shared/ReactSharedInternals';
import {HostRoot} from 'shared/ReactWorkTags';

import {NoWork, Sync} from './ReactFiberExpirationTime';
import {readContext} from './ReactFiberNewContext';
Expand All @@ -45,7 +46,8 @@ import {
warnIfNotScopedWithMatchingAct,
markRenderEventTimeAndConfig,
markUnprocessedUpdateTime,
getMutableSourceMetadata,
getMutableSourcePendingExpirationTime,
warnAboutUpdateOnUnmountedFiberInDEV,
} from './ReactFiberWorkLoop';

import invariant from 'shared/invariant';
Expand Down Expand Up @@ -897,13 +899,15 @@ function useMutableSourceImpl<S>(
}
}

const metadata = getMutableSourceMetadata(source);
const pendingExpirationTime = getMutableSourcePendingExpirationTime(source);

// Is it safe to read from this source during the current render?
// If the source has not yet been subscribed to, we can use the version number to determine this.
// Else we can use the expiration time as an indicator of any future scheduled updates.
let isSafeToReadFromSource = false;
if (metadata.subscriptionCount === 0) {

// Is it safe to read from this source during the current render?
// If the source has pending updates, we can use the current render's expiration
// time to determine if it's safe to read again from the source.
// If there are no pending updates, we can use the work-in-progress version.
if (pendingExpirationTime === null) {
const lastReadVersion = getWorkInProgressVersion(source);
if (lastReadVersion === null) {
// This is the only case where we need to actually update the version number.
Expand All @@ -926,8 +930,8 @@ function useMutableSourceImpl<S>(
);

isSafeToReadFromSource =
metadata.expirationTime === NoWork ||
metadata.expirationTime >= expirationTime;
pendingExpirationTime === NoWork ||
pendingExpirationTime >= expirationTime;
}

let prevMemoizedState = ((hook.memoizedState: any): ?MutableSourceState<S>);
Expand Down Expand Up @@ -977,22 +981,43 @@ function useMutableSourceImpl<S>(

const create = () => {
const scheduleUpdate = () => {
const currentTime = requestCurrentTimeForUpdate();
const suspenseConfig = requestCurrentSuspenseConfig();
const expirationTime = computeExpirationForFiber(
currentTime,
fiber,
suspenseConfig,
);
let node = fiber;
let root = null;
while (node !== null) {
if (node.tag === HostRoot) {
root = node.stateNode;
break;
}
node = node.return;
}

// Make sure reads during future renders will know there's a pending update.
// This will prevent a higher priority update from reading a newer version of the source,
// and causing a tear between that render and previous renders.
if (expirationTime > metadata.expirationTime) {
metadata.expirationTime = expirationTime;
if (root === null) {
warnAboutUpdateOnUnmountedFiberInDEV(fiber);
return;
}

scheduleWork(fiber, expirationTime);
const alreadyScheduledExpirationTime = root.mutableSourcePendingUpdateMap.get(
source,
);

// If an update is already scheduled for this source, re-use the same priority.
if (alreadyScheduledExpirationTime !== undefined) {
scheduleWork(fiber, alreadyScheduledExpirationTime);
} else {
const currentTime = requestCurrentTimeForUpdate();
const suspenseConfig = requestCurrentSuspenseConfig();
const expirationTime = computeExpirationForFiber(
currentTime,
fiber,
suspenseConfig,
);
scheduleWork(fiber, expirationTime);

// Make sure reads during future renders will know there's a pending update.
// This will prevent a higher priority update from reading a newer version of the source,
// and causing a tear between that render and previous renders.
root.mutableSourcePendingUpdateMap.set(source, expirationTime);
}
};

// Was the source mutated between when we rendered and when we're subscribing?
Expand All @@ -1002,16 +1027,8 @@ function useMutableSourceImpl<S>(
scheduleUpdate();
}

const unsubscribe = subscribe(scheduleUpdate);
metadata.subscriptionCount++;

memoizedState.destroy = () => {
metadata.subscriptionCount--;

// TODO (useMutableSource) If count is 0, flag this source for possible cleanup.

unsubscribe();
};
// Unsubscribe on destroy.
memoizedState.destroy = subscribe(scheduleUpdate);

return memoizedState.destroy;
};
Expand Down
6 changes: 3 additions & 3 deletions packages/react-reconciler/src/ReactFiberRoot.js
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ import type {Thenable} from './ReactFiberWorkLoop';
import type {Interaction} from 'scheduler/src/Tracing';
import type {SuspenseHydrationCallbacks} from './ReactFiberSuspenseComponent';
import type {ReactPriorityLevel} from './SchedulerWithReactIntegration';
import type {MutableSourceMetadataMap} from 'shared/ReactMutableSource';
import type {MutableSourcePendingUpdateMap} from 'shared/ReactMutableSource';

import {noTimeout} from './ReactFiberHostConfig';
import {createHostRootFiber} from './ReactFiber';
Expand Down Expand Up @@ -77,7 +77,7 @@ type BaseFiberRootProperties = {|
lastExpiredTime: ExpirationTime,
// Used by useMutableSource hook to avoid tearing within this root
// when external, mutable sources are read from during render.
mutableSourceMetadata: MutableSourceMetadataMap,
mutableSourcePendingUpdateMap: MutableSourcePendingUpdateMap,
|};

// The following attributes are only used by interaction tracing builds.
Expand Down Expand Up @@ -127,7 +127,7 @@ function FiberRootNode(containerInfo, tag, hydrate) {
this.nextKnownPendingLevel = NoWork;
this.lastPingedTime = NoWork;
this.lastExpiredTime = NoWork;
this.mutableSourceMetadata = new Map();
this.mutableSourcePendingUpdateMap = new Map();

if (enableSchedulerTracing) {
this.interactionThreadID = unstable_getThreadID();
Expand Down
46 changes: 18 additions & 28 deletions packages/react-reconciler/src/ReactFiberWorkLoop.js
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Original file line number Diff line number Diff line change
Expand Up @@ -14,10 +14,7 @@ import type {ReactPriorityLevel} from './SchedulerWithReactIntegration';
import type {Interaction} from 'scheduler/src/Tracing';
import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
import type {SuspenseState} from './ReactFiberSuspenseComponent';
import type {
MutableSource,
MutableSourceMetadata,
} from 'shared/ReactMutableSource';
import type {MutableSource} from 'shared/ReactMutableSource';

import {
initializeWorkInProgressVersionMap as initializeMutableSourceWorkInProgressVersionMap,
Expand Down Expand Up @@ -299,24 +296,14 @@ let spawnedWorkDuringRender: null | Array<ExpirationTime> = null;
// receive the same expiration time. Otherwise we get tearing.
let currentEventTime: ExpirationTime = NoWork;

export function getMutableSourceMetadata(
export function getMutableSourcePendingExpirationTime(
source: MutableSource,
): MutableSourceMetadata {
): ExpirationTime | null {
invariant(workInProgressRoot !== null, 'Expected a work-in-progress root.');

let metadata = workInProgressRoot.mutableSourceMetadata.get(source);
if (metadata !== undefined) {
return metadata;
} else {
metadata = {
expirationTime: NoWork,
subscriptionCount: 0,
};

workInProgressRoot.mutableSourceMetadata.set(source, metadata);

return ((metadata: any): MutableSourceMetadata);
}
const expirationTime = workInProgressRoot.mutableSourcePendingUpdateMap.get(
source,
);
return expirationTime !== undefined ? expirationTime : null;
}

export function requestCurrentTimeForUpdate() {
Expand Down Expand Up @@ -402,10 +389,7 @@ export function computeExpirationForFiber(
return expirationTime;
}

export function scheduleUpdateOnFiber(
fiber: Fiber,
expirationTime: ExpirationTime,
) {
function scheduleUpdateOnFiber(fiber: Fiber, expirationTime: ExpirationTime) {
checkForNestedUpdates();
warnAboutInvalidUpdatesOnClassComponentsInDEV(fiber);

Expand Down Expand Up @@ -2027,6 +2011,15 @@ function commitRootImpl(root, renderPriorityLevel) {
nestedUpdateCount = 0;
}

// Remove pending mutable source entries that we've completed processing.
root.mutableSourcePendingUpdateMap.forEach(
(pendingExpirationTime, source) => {
if (pendingExpirationTime <= expirationTime) {
root.mutableSourcePendingUpdateMap.delete(source);
}
},
);

resetMutableSourceWorkInProgressVersionMap();

onCommitRoot(finishedWork.stateNode, expirationTime);
Expand Down Expand Up @@ -2280,9 +2273,6 @@ function flushPassiveEffectsImpl() {
finishPendingInteractions(root, expirationTime);
}

// TODO (useMutableSource) Remove metadata for mutable sources that are no longer in use.
// This check comes after passive effects, because that's when sources are unsubscribed from.

executionContext = prevExecutionContext;

flushSyncCallbackQueue();
Expand Down Expand Up @@ -2626,7 +2616,7 @@ function checkForInterruption(
}

let didWarnStateUpdateForUnmountedComponent: Set<string> | null = null;
function warnAboutUpdateOnUnmountedFiberInDEV(fiber) {
export function warnAboutUpdateOnUnmountedFiberInDEV(fiber: Fiber) {
if (__DEV__) {
const tag = fiber.tag;
if (
Expand Down
2 changes: 0 additions & 2 deletions packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2098,8 +2098,6 @@ describe('ReactHooksWithNoopRenderer', () => {
});
expect(Scheduler).toHaveYielded(['a:two', 'b:two', 'Sync effect']);
});

// TODO (useMutableSource) Edge case: make sure we don't leak on root Map (how to test this without internals?)
});

describe('useCallback', () => {
Expand Down
23 changes: 6 additions & 17 deletions packages/shared/ReactMutableSource.js
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Original file line number Diff line number Diff line change
Expand Up @@ -20,23 +20,12 @@ export type MutableSourceHookConfig<S> = {|
subscribe: (callback: Function) => () => void,
|};

export type MutableSourceMetadata = {|
// Expiration time of most recently scheduled update.
// Used to determine if a source is safe to read during updates.
// If the render’s expiration time is ≤ this value,
// the source has not changed since the last render and is safe to read from.
expirationTime: ExpirationTime,

// Number of hooks that are subscribed as of the most recently committed render.
// This value is used to determine when a source is no longer in use,
// and should be removed from the root map to avoid a memory leak.
subscriptionCount: number,
|};

export type MutableSourceMetadataMap = Map<
MutableSource,
MutableSourceMetadata,
>;
// Tracks expiration time for all mutable sources with pending updates.
// Used to determine if a source is safe to read during updates.
// If there are no entries in this map for a given source,
// or if the current render’s expiration time is ≤ this value,
// it is safe to read from the source without tearing.
export type MutableSourcePendingUpdateMap = Map<MutableSource, ExpirationTime>;

// Tracks the version of each source at the time it was most recently read.
// Used to determine if a source is safe to read from before it has been subscribed to.
Expand Down

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