diff --git a/src/profile-logic/call-tree.ts b/src/profile-logic/call-tree.ts
index 57495bec52..75edb0346b 100644
--- a/src/profile-logic/call-tree.ts
+++ b/src/profile-logic/call-tree.ts
@@ -34,7 +34,7 @@ import { ResourceType } from 'firefox-profiler/types';
 import ExtensionIcon from '../../res/img/svg/extension.svg';
 import { formatCallNodeNumber, formatPercent } from '../utils/format-numbers';
 import { assertExhaustiveCheck, ensureExists } from '../utils/types';
-import { checkBit } from '../utils/bitset';
+import { type BitSet, checkBit, makeBitSet, setBit } from '../utils/bitset';
 import * as ProfileData from './profile-data';
 import type { CallTreeSummaryStrategy } from '../types/actions';
 import type { CallNodeInfo, CallNodeInfoInverted } from './call-node-info';
@@ -43,7 +43,7 @@ import { getBottomBoxInfoForCallNode } from './bottom-box';
 type CallNodeChildren = IndexIntoCallNodeTable[];
 
 export type CallTreeTimingsNonInverted = {
-  callNodeHasChildren: Uint8Array;
+  callNodeHasChildren: BitSet;
   self: Float64Array;
   total: Float64Array;
   rootTotalSummary: number; // sum of absolute values, this is used for computing percentages
@@ -61,7 +61,7 @@ export type CallTreeTimingsInverted = {
   rootTotalSummary: number;
   sortedRoots: IndexIntoFuncTable[];
   totalPerRootFunc: Float64Array;
-  hasChildrenPerRootFunc: Uint8Array;
+  hasChildrenPerRootFunc: BitSet;
 };
 
 export type CallTreeTimingsFunctionList = {
@@ -119,7 +119,7 @@ export class CallTreeInternalNonInverted implements CallTreeInternal {
   _callNodeInfo: CallNodeInfo;
   _callNodeTable: CallNodeTable;
   _callTreeTimings: CallTreeTimingsNonInverted;
-  _callNodeHasChildren: Uint8Array; // A table column matching the callNodeTable
+  _callNodeHasChildren: BitSet; // A table column matching the callNodeTable
 
   constructor(
     callNodeInfo: CallNodeInfo,
@@ -157,9 +157,12 @@ export class CallTreeInternalNonInverted implements CallTreeInternal {
       childCallNodeIndex = this._callNodeTable.nextSibling[childCallNodeIndex]
     ) {
       const childTotalSummary = this._callTreeTimings.total[childCallNodeIndex];
-      const childHasChildren = this._callNodeHasChildren[childCallNodeIndex];
+      const childHasChildren = checkBit(
+        this._callNodeHasChildren,
+        childCallNodeIndex
+      );
 
-      if (childTotalSummary !== 0 || childHasChildren !== 0) {
+      if (childTotalSummary !== 0 || childHasChildren) {
         children.push(childCallNodeIndex);
       }
     }
@@ -172,7 +175,7 @@ export class CallTreeInternalNonInverted implements CallTreeInternal {
   }
 
   hasChildren(callNodeIndex: IndexIntoCallNodeTable): boolean {
-    return this._callNodeHasChildren[callNodeIndex] !== 0;
+    return checkBit(this._callNodeHasChildren, callNodeIndex);
   }
 
   getSelfAndTotal(callNodeIndex: IndexIntoCallNodeTable): SelfAndTotal {
@@ -242,7 +245,7 @@ class CallTreeInternalInverted implements CallTreeInternal {
   _callNodeSelf: Float64Array;
   _rootNodes: IndexIntoCallNodeTable[];
   _totalPerRootFunc: Float64Array;
-  _hasChildrenPerRootFunc: Uint8Array;
+  _hasChildrenPerRootFunc: BitSet;
   _totalAndHasChildrenPerNonRootNode: Map<
     IndexIntoCallNodeTable,
     TotalAndHasChildren
@@ -268,7 +271,7 @@ class CallTreeInternalInverted implements CallTreeInternal {
 
   hasChildren(callNodeIndex: IndexIntoCallNodeTable): boolean {
     if (this._callNodeInfo.isRoot(callNodeIndex)) {
-      return this._hasChildrenPerRootFunc[callNodeIndex] !== 0;
+      return checkBit(this._hasChildrenPerRootFunc, callNodeIndex);
     }
     return this._getTotalAndHasChildren(callNodeIndex).hasChildren;
   }
@@ -790,8 +793,8 @@ export function computeCallTreeTimingsInverted(
   const callNodeTableFuncCol = callNodeTable.func;
   const callNodeTableDepthCol = callNodeTable.depth;
   const totalPerRootFunc = new Float64Array(funcCount);
-  const hasChildrenPerRootFunc = new Uint8Array(funcCount);
-  const seenPerRootFunc = new Uint8Array(funcCount);
+  const hasChildrenPerRootFunc = makeBitSet(funcCount);
+  const seenPerRootFunc = makeBitSet(funcCount);
   const sortedRoots = [];
   for (let i = 0; i < callNodeSelf.length; i++) {
     const self = callNodeSelf[i];
@@ -805,12 +808,12 @@ export function computeCallTreeTimingsInverted(
     const func = callNodeTableFuncCol[i];
 
     totalPerRootFunc[func] += self;
-    if (seenPerRootFunc[func] === 0) {
-      seenPerRootFunc[func] = 1;
+    if (!checkBit(seenPerRootFunc, func)) {
+      setBit(seenPerRootFunc, func);
       sortedRoots.push(func);
     }
     if (callNodeTableDepthCol[i] !== 0) {
-      hasChildrenPerRootFunc[func] = 1;
+      setBit(hasChildrenPerRootFunc, func);
     }
   }
   sortedRoots.sort(
@@ -861,7 +864,7 @@ export function computeCallTreeTimingsNonInverted(
 
   // Compute the following variables:
   const callNodeTotal = new Float64Array(callNodeTable.length);
-  const callNodeHasChildren = new Uint8Array(callNodeTable.length);
+  const callNodeHasChildren = makeBitSet(callNodeTable.length);
 
   // We loop the call node table in reverse, so that we find the children
   // before their parents, and the total is known at the time we reach a
@@ -874,7 +877,7 @@ export function computeCallTreeTimingsNonInverted(
     // callNodeTotal[callNodeIndex] is the sum of our children's totals.
     // Compute this node's total by adding this node's self.
     const total = callNodeTotal[callNodeIndex] + callNodeSelf[callNodeIndex];
-    const hasChildren = callNodeHasChildren[callNodeIndex] !== 0;
+    const hasChildren = checkBit(callNodeHasChildren, callNodeIndex);
     const hasTotalValue = total !== 0;
 
     callNodeTotal[callNodeIndex] = total;
@@ -886,7 +889,7 @@ export function computeCallTreeTimingsNonInverted(
     const prefixCallNode = callNodeTable.prefix[callNodeIndex];
     if (prefixCallNode !== -1) {
       callNodeTotal[prefixCallNode] += total;
-      callNodeHasChildren[prefixCallNode] = 1;
+      setBit(callNodeHasChildren, prefixCallNode);
     }
   }
 
@@ -940,7 +943,7 @@ function _computeFuncTotal(
   // The set of "functions with potentially non-zero totals", stored as an array.
   const seenFuncs = [];
   // seenPerFunc[func] stores whether seenFuncs.includes(func).
-  const seenPerFunc = new Uint8Array(funcCount);
+  const seenPerFunc = makeBitSet(funcCount);
 
   // We loop the call node table in reverse, so that we find the children
   // before their parents, and the total is known at the time we reach a
@@ -979,8 +982,8 @@ function _computeFuncTotal(
       funcTotal[func] += total;
 
       // Add this func to the set of funcs with potentially non-zero totals.
-      if (seenPerFunc[func] === 0) {
-        seenPerFunc[func] = 1;
+      if (!checkBit(seenPerFunc, func)) {
+        setBit(seenPerFunc, func);
         seenFuncs.push(func);
       }
     }
diff --git a/src/profile-logic/profile-data.ts b/src/profile-logic/profile-data.ts
index 49a521c9f1..51edacc88a 100644
--- a/src/profile-logic/profile-data.ts
+++ b/src/profile-logic/profile-data.ts
@@ -520,7 +520,7 @@ function _computeCallNodeTableExtraColumns(
   const innerWindowIDCol = new Float64Array(callNodeCount);
   const inlinedIntoCol = new Int32Array(callNodeCount);
 
-  const haveFilled = new Uint8Array(callNodeCount);
+  const haveFilled = makeBitSet(callNodeCount);
 
   for (let stackIndex = 0; stackIndex < stackCount; stackIndex++) {
     const category = stackTableCategoryCol[stackIndex];
@@ -530,7 +530,7 @@ function _computeCallNodeTableExtraColumns(
 
     const callNodeIndex = stackIndexToCallNodeIndex[stackIndex];
 
-    if (haveFilled[callNodeIndex] === 0) {
+    if (!checkBit(haveFilled, callNodeIndex)) {
       funcCol[callNodeIndex] = frameTableFuncCol[frameIndex];
 
       categoryCol[callNodeIndex] = category;
@@ -544,7 +544,7 @@ function _computeCallNodeTableExtraColumns(
         innerWindowIDCol[callNodeIndex] = innerWindowID;
       }
 
-      haveFilled[callNodeIndex] = 1;
+      setBit(haveFilled, callNodeIndex);
     } else {
       // Resolve category conflicts, by resetting a conflicting subcategory or
       // category to the default category.
diff --git a/src/profile-logic/symbolication.ts b/src/profile-logic/symbolication.ts
index 3186fb7b3a..ae423e317e 100644
--- a/src/profile-logic/symbolication.ts
+++ b/src/profile-logic/symbolication.ts
@@ -32,6 +32,7 @@ import type {
 import { PathSet } from '../utils/path';
 import { StringTable } from '../utils/string-table';
 import { updateRawThreadStacks } from './profile-data';
+import { type BitSet, makeBitSet, setBit, checkBit } from '../utils/bitset';
 
 // Contains functions to symbolicate a profile.
 
@@ -411,7 +412,7 @@ function finishSymbolicationForLib(
 //      - stack F with frame 5
 function _computeStackTableWithAddedExpansionStacks(
   stackTable: RawStackTable,
-  shouldStacksWithThisOldFrameBeRemoved: Uint8Array,
+  shouldStacksWithThisOldFrameBeRemoved: BitSet,
   frameIndexToInlineExpansionFrames: Map<
     IndexIntoFrameTable,
     IndexIntoFrameTable[]
@@ -427,7 +428,7 @@ function _computeStackTableWithAddedExpansionStacks(
     const oldPrefix = stackTable.prefix[stack];
     const newPrefixOrMinusOne =
       oldPrefix === null ? -1 : oldStackToNewStack[oldPrefix];
-    if (shouldStacksWithThisOldFrameBeRemoved[oldFrame] !== 0) {
+    if (checkBit(shouldStacksWithThisOldFrameBeRemoved, oldFrame)) {
       // Don't add this stack node to the new stack table. Instead, make it
       // so that this node's children use our prefix as their prefix.
       oldStackToNewStack[stack] = newPrefixOrMinusOne;
@@ -470,7 +471,7 @@ export function applySymbolicationSteps(
 } {
   const oldFuncToNewFuncsMap: FuncToFuncsMap = new Map();
   const frameCount = oldShared.frameTable.length;
-  const shouldStacksWithThisFrameBeRemoved = new Uint8Array(frameCount);
+  const shouldStacksWithThisFrameBeRemoved = makeBitSet(frameCount);
   const frameIndexToInlineExpansionFrames = new Map<
     IndexIntoFrameTable,
     IndexIntoFrameTable[]
@@ -541,7 +542,7 @@ function _partiallyApplySymbolicationStep(
   shared: RawProfileSharedData,
   symbolicationStepInfo: SymbolicationStepInfo,
   oldFuncToNewFuncsMap: FuncToFuncsMap,
-  shouldStacksWithThisFrameBeRemoved: Uint8Array,
+  shouldStacksWithThisFrameBeRemoved: BitSet,
   frameIndexToInlineExpansionFrames: Map<
     IndexIntoFrameTable,
     IndexIntoFrameTable[]
@@ -585,7 +586,7 @@ function _partiallyApplySymbolicationStep(
   for (const frameIndex of allFramesForThisLib) {
     if (oldFrameTable.inlineDepth[frameIndex] > 0) {
       inlinedFrames.push(frameIndex);
-      shouldStacksWithThisFrameBeRemoved[frameIndex] = 1;
+      setBit(shouldStacksWithThisFrameBeRemoved, frameIndex);
     } else {
       nonInlinedFrames.push(frameIndex);
     }
diff --git a/src/profile-logic/transforms.ts b/src/profile-logic/transforms.ts
index 604b7f1179..771991998e 100644
--- a/src/profile-logic/transforms.ts
+++ b/src/profile-logic/transforms.ts
@@ -54,6 +54,7 @@ import {
   translateFuncIndex,
   translateResourceIndex,
 } from './index-translation';
+import { checkBit, makeBitSet, setBit } from 'firefox-profiler/utils/bitset';
 
 /**
  * This file contains the functions and logic for working with and applying transforms
@@ -926,9 +927,7 @@ export function dropFunction(
   const { stackTable, frameTable } = thread;
 
   // Go through each stack, and label it as containing the function or not.
-  // stackContainsFunc is a stackIndex => bool map, implemented as a U8 typed
-  // array for better performance. 0 means false, 1 means true.
-  const stackContainsFunc = new Uint8Array(stackTable.length);
+  const stackContainsFunc = makeBitSet(stackTable.length);
   for (let stackIndex = 0; stackIndex < stackTable.length; stackIndex++) {
     const prefix = stackTable.prefix[stackIndex];
     const frameIndex = stackTable.frame[stackIndex];
@@ -937,15 +936,15 @@ export function dropFunction(
       // This is the function we want to remove.
       funcIndex === funcIndexToDrop ||
       // The parent of this stack contained the function.
-      (prefix !== null && stackContainsFunc[prefix] === 1)
+      (prefix !== null && checkBit(stackContainsFunc, prefix))
     ) {
-      stackContainsFunc[stackIndex] = 1;
+      setBit(stackContainsFunc, stackIndex);
     }
   }
 
   return updateThreadStacks(thread, stackTable, (stack) =>
     // Drop the stacks that contain that function.
-    stack !== null && stackContainsFunc[stack] === 1 ? null : stack
+    stack !== null && checkBit(stackContainsFunc, stack) ? null : stack
   );
 }
 
@@ -1214,19 +1213,19 @@ export function collapseFunctionSubtree(
 ): Thread {
   const { stackTable, frameTable } = thread;
   const oldStackToNewStack = new Int32Array(stackTable.length);
-  const isInCollapsedSubtree = new Uint8Array(stackTable.length);
+  const isInCollapsedSubtree = makeBitSet(stackTable.length);
 
   for (let stackIndex = 0; stackIndex < stackTable.length; stackIndex++) {
     const prefix = stackTable.prefix[stackIndex];
-    if (prefix !== null && isInCollapsedSubtree[prefix] !== 0) {
+    if (prefix !== null && checkBit(isInCollapsedSubtree, prefix)) {
       oldStackToNewStack[stackIndex] = oldStackToNewStack[prefix];
-      isInCollapsedSubtree[stackIndex] = 1;
+      setBit(isInCollapsedSubtree, stackIndex);
     } else {
       oldStackToNewStack[stackIndex] = stackIndex;
       const frameIndex = stackTable.frame[stackIndex];
       const funcIndex = frameTable.func[frameIndex];
       if (funcToCollapse === funcIndex) {
-        isInCollapsedSubtree[stackIndex] = 1;
+        setBit(isInCollapsedSubtree, stackIndex);
       }
     }
   }
@@ -1740,7 +1739,7 @@ export function funcHasRecursiveCall(
   funcToCheck: IndexIntoFuncTable
 ) {
   // Set of stack indices that are funcToCheck or have a funcToCheck ancestor.
-  const ancestorOfCallNodeContainsFuncToCheck = new Uint8Array(
+  const ancestorOfCallNodeContainsFuncToCheck = makeBitSet(
     callNodeTable.length
   );
 
@@ -1748,16 +1747,16 @@ export function funcHasRecursiveCall(
     const prefix = callNodeTable.prefix[i];
     const funcIndex = callNodeTable.func[i];
     const recursivePrefix =
-      prefix !== -1 && ancestorOfCallNodeContainsFuncToCheck[prefix] !== 0;
+      prefix !== -1 && checkBit(ancestorOfCallNodeContainsFuncToCheck, prefix);
 
     if (funcToCheck === funcIndex) {
       if (recursivePrefix) {
         // This function matches and so did one of its ancestors.
         return true;
       }
-      ancestorOfCallNodeContainsFuncToCheck[i] = 1;
+      setBit(ancestorOfCallNodeContainsFuncToCheck, i);
     } else if (recursivePrefix) {
-      ancestorOfCallNodeContainsFuncToCheck[i] = 1;
+      setBit(ancestorOfCallNodeContainsFuncToCheck, i);
     }
   }
   return false;
diff --git a/src/test/store/__snapshots__/profile-view.test.ts.snap b/src/test/store/__snapshots__/profile-view.test.ts.snap
index f04baf9582..179d6e9125 100644
--- a/src/test/store/__snapshots__/profile-view.test.ts.snap
+++ b/src/test/store/__snapshots__/profile-view.test.ts.snap
@@ -2069,16 +2069,8 @@ CallTree {
   "_children": Array [],
   "_displayDataByIndex": Map {},
   "_internal": CallTreeInternalNonInverted {
-    "_callNodeHasChildren": Uint8Array [
-      1,
-      1,
-      0,
-      0,
-      0,
-      1,
-      0,
-      0,
-      0,
+    "_callNodeHasChildren": Int32Array [
+      35,
     ],
     "_callNodeInfo": CallNodeInfoNonInverted {
       "_cache": Map {},
@@ -2301,16 +2293,8 @@ CallTree {
       ],
     },
     "_callTreeTimings": Object {
-      "callNodeHasChildren": Uint8Array [
-        1,
-        1,
-        0,
-        0,
-        0,
-        1,
-        0,
-        0,
-        0,
+      "callNodeHasChildren": Int32Array [
+        35,
       ],
       "rootTotalSummary": 2,
       "self": Float64Array [
diff --git a/src/test/unit/profile-tree.test.ts b/src/test/unit/profile-tree.test.ts
index f50cd99fe8..f71d94784d 100644
--- a/src/test/unit/profile-tree.test.ts
+++ b/src/test/unit/profile-tree.test.ts
@@ -20,6 +20,7 @@ import {
   getSampleIndexToCallNodeIndex,
 } from '../../profile-logic/profile-data';
 import { ResourceType } from 'firefox-profiler/types';
+import { makeBitSet, setBit } from '../../utils/bitset';
 import {
   callTreeFromProfile,
   functionListTreeFromProfile,
@@ -79,11 +80,16 @@ describe('unfiltered call tree', function () {
           callNodeInfo.getCallNodeTable().length
         )
       );
+      const expectedHasChildren = makeBitSet(9);
+      // Nodes 0, 1, 2, 3, 5, 7 have children.
+      for (const i of [0, 1, 2, 3, 5, 7]) {
+        setBit(expectedHasChildren, i);
+      }
       expect(callTreeTimings).toEqual({
         type: 'NON_INVERTED',
         timings: {
           rootTotalSummary: 3,
-          callNodeHasChildren: new Uint8Array([1, 1, 1, 1, 0, 1, 0, 1, 0]),
+          callNodeHasChildren: expectedHasChildren,
           self: new Float64Array([0, 0, 0, 0, 1, 0, 1, 0, 1]),
           total: new Float64Array([3, 3, 2, 1, 1, 1, 1, 1, 1]),
         },