diff --git a/src/webgpu/api/operation/memory_sync/buffer/buffer_sync_test.ts b/src/webgpu/api/operation/memory_sync/buffer/buffer_sync_test.ts
index e18dc59abf2e..6dda4b7205d9 100644
--- a/src/webgpu/api/operation/memory_sync/buffer/buffer_sync_test.ts
+++ b/src/webgpu/api/operation/memory_sync/buffer/buffer_sync_test.ts
@@ -285,6 +285,7 @@ export class BufferSyncTest extends GPUTest {
 
   // Create a 1x1 texture, and initialize it to a specified value for all elements.
   async createTextureWithValue(initValue: number): Promise<GPUTexture> {
+    // This is not hot in profiles; optimize if this gets used more heavily.
     const data = new Uint32Array(1).fill(initValue);
     const texture = this.trackForCleanup(
       this.device.createTexture({
@@ -446,6 +447,7 @@ export class BufferSyncTest extends GPUTest {
 
   // Write buffer via writeBuffer API on queue
   writeByWriteBuffer(buffer: GPUBuffer, value: number) {
+    // This is not hot in profiles; optimize if this gets used more heavily.
     const data = new Uint32Array(1).fill(value);
     this.device.queue.writeBuffer(buffer, 0, data);
   }
@@ -919,12 +921,14 @@ export class BufferSyncTest extends GPUTest {
   }
 
   verifyData(buffer: GPUBuffer, expectedValue: number) {
+    // This is not hot in profiles; optimize if this gets used more heavily.
     const bufferData = new Uint32Array(1);
     bufferData[0] = expectedValue;
     this.expectGPUBufferValuesEqual(buffer, bufferData);
   }
 
   verifyDataTwoValidValues(buffer: GPUBuffer, expectedValue1: number, expectedValue2: number) {
+    // This is not hot in profiles; optimize if this gets used more heavily.
     const bufferData1 = new Uint32Array(1);
     bufferData1[0] = expectedValue1;
     const bufferData2 = new Uint32Array(1);
diff --git a/src/webgpu/shader/execution/flow_control/harness.ts b/src/webgpu/shader/execution/flow_control/harness.ts
index 94dfcdfc4d8f..885e32bd4aec 100644
--- a/src/webgpu/shader/execution/flow_control/harness.ts
+++ b/src/webgpu/shader/execution/flow_control/harness.ts
@@ -221,9 +221,8 @@ ${main_wgsl.extra}
 
         // returns a string that shows the outputted values to help understand the whole trace.
         const print_output_value = () => {
-          return `Output values (length: ${outputCount}): ${outputs.data
-            .slice(1, outputCount + 1)
-            .join(', ')}`;
+          const subarray = outputs.data.subarray(1, outputCount + 1);
+          return `Output values (length: ${outputCount}): ${subarray.join(', ')}`;
         };
 
         // returns a colorized string of the expect_order() call, highlighting
diff --git a/src/webgpu/shader/execution/memory_model/memory_model_setup.ts b/src/webgpu/shader/execution/memory_model/memory_model_setup.ts
index d2dab32ecbb1..f8e5b9034cb4 100644
--- a/src/webgpu/shader/execution/memory_model/memory_model_setup.ts
+++ b/src/webgpu/shader/execution/memory_model/memory_model_setup.ts
@@ -203,10 +203,10 @@ export class MemoryModelTester {
         size: testLocationsSize,
         usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.STORAGE,
       }),
-      srcBuf: this.test.makeBufferWithContents(
-        new Uint32Array(testLocationsSize).fill(0),
-        GPUBufferUsage.COPY_SRC
-      ),
+      srcBuf: this.test.device.createBuffer({
+        size: testLocationsSize,
+        usage: GPUBufferUsage.COPY_SRC,
+      }),
       size: testLocationsSize,
     };
 
@@ -216,10 +216,10 @@ export class MemoryModelTester {
         size: readResultsSize,
         usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.STORAGE,
       }),
-      srcBuf: this.test.makeBufferWithContents(
-        new Uint32Array(readResultsSize).fill(0),
-        GPUBufferUsage.COPY_SRC
-      ),
+      srcBuf: this.test.device.createBuffer({
+        size: readResultsSize,
+        usage: GPUBufferUsage.COPY_SRC,
+      }),
       size: readResultsSize,
     };
 
@@ -229,10 +229,10 @@ export class MemoryModelTester {
         size: testResultsSize,
         usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_SRC,
       }),
-      srcBuf: this.test.makeBufferWithContents(
-        new Uint32Array(testResultsSize).fill(0),
-        GPUBufferUsage.COPY_SRC
-      ),
+      srcBuf: this.test.device.createBuffer({
+        size: testResultsSize,
+        usage: GPUBufferUsage.COPY_SRC,
+      }),
       size: testResultsSize,
     };
 
@@ -255,10 +255,10 @@ export class MemoryModelTester {
         size: barrierSize,
         usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.STORAGE,
       }),
-      srcBuf: this.test.makeBufferWithContents(
-        new Uint32Array(barrierSize).fill(0),
-        GPUBufferUsage.COPY_SRC
-      ),
+      srcBuf: this.test.device.createBuffer({
+        size: barrierSize,
+        usage: GPUBufferUsage.COPY_SRC,
+      }),
       size: barrierSize,
     };
 
@@ -268,10 +268,10 @@ export class MemoryModelTester {
         size: scratchpadSize,
         usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.STORAGE,
       }),
-      srcBuf: this.test.makeBufferWithContents(
-        new Uint32Array(scratchpadSize).fill(0),
-        GPUBufferUsage.COPY_SRC
-      ),
+      srcBuf: this.test.device.createBuffer({
+        size: scratchpadSize,
+        usage: GPUBufferUsage.COPY_SRC,
+      }),
       size: scratchpadSize,
     };
 
diff --git a/src/webgpu/web_platform/reftests/canvas_colorspace.html.ts b/src/webgpu/web_platform/reftests/canvas_colorspace.html.ts
index d4b5b24e1e82..3a763e8c28b3 100644
--- a/src/webgpu/web_platform/reftests/canvas_colorspace.html.ts
+++ b/src/webgpu/web_platform/reftests/canvas_colorspace.html.ts
@@ -5,6 +5,7 @@ import { kCanvasAlphaModes, kCanvasColorSpaces } from '../../capability_info.js'
 import { runRefTest } from './gpu_ref_test.js';
 
 function bgra8UnormFromRgba8Unorm(rgba8Unorm: Uint8Array) {
+  // This is used only once. May need to optimize if reused.
   const bgra8Unorm = rgba8Unorm.slice();
   for (let i = 0; i < bgra8Unorm.length; i += 4) {
     [bgra8Unorm[i], bgra8Unorm[i + 2]] = [bgra8Unorm[i + 2], bgra8Unorm[i]];
@@ -13,6 +14,7 @@ function bgra8UnormFromRgba8Unorm(rgba8Unorm: Uint8Array) {
 }
 
 function rgba16floatFromRgba8unorm(rgba8Unorm: Uint8Array) {
+  // This is used only once. May need to optimize if reused.
   const rgba16Float = new Float16Array(rgba8Unorm.length);
   for (let i = 0; i < rgba8Unorm.length; ++i) {
     rgba16Float[i] = rgba8Unorm[i] / 255;
diff --git a/src/webgpu/web_platform/reftests/canvas_complex.html.ts b/src/webgpu/web_platform/reftests/canvas_complex.html.ts
index a8da9cb5b36d..2c17be88754e 100644
--- a/src/webgpu/web_platform/reftests/canvas_complex.html.ts
+++ b/src/webgpu/web_platform/reftests/canvas_complex.html.ts
@@ -55,6 +55,7 @@ export function run(
         size: rows * bytesPerRow,
         usage: GPUBufferUsage.COPY_SRC,
       });
+      // These are run only once per test, so there are no wasted reallocations below.
       let red: Uint8Array | Uint16Array;
       let green: Uint8Array | Uint16Array;
       let blue: Uint8Array | Uint16Array;