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Split down timestamp query example into multiple files
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| // A minimalistic perf timer class that computes mean + stddev online | ||
| export default class PerfCounter { | ||
| sampleCount: number; | ||
| accumulated: number; | ||
| accumulatedSq: number; | ||
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| constructor() { | ||
| this.sampleCount = 0; | ||
| this.accumulated = 0; | ||
| this.accumulatedSq = 0; | ||
| } | ||
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| addSample(value: number) { | ||
| this.sampleCount += 1; | ||
| this.accumulated += value; | ||
| this.accumulatedSq += value * value; | ||
| } | ||
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| getAverage(): number { | ||
| return this.sampleCount === 0 ? 0 : this.accumulated / this.sampleCount; | ||
| } | ||
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| getStddev(): number { | ||
| if (this.sampleCount === 0) return 0; | ||
| const avg = this.getAverage(); | ||
| const variance = this.accumulatedSq / this.sampleCount - avg * avg; | ||
| return Math.sqrt(Math.max(0.0, variance)); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| // Regroups all timestamp-related operations and resources. | ||
| export default class TimestampQueryManager { | ||
| // The device may not support timestamp queries, on which case this whole | ||
| // class does nothing. | ||
| timestampSupported: boolean | ||
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| // Number of timestamp counters | ||
| timestampCount: number | ||
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| // The query objects. This is meant to be used in a ComputePassDescriptor's | ||
| // or RenderPassDescriptor's 'timestampWrites' field. | ||
| timestampQuerySet: GPUQuerySet | ||
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| // A buffer where to store query results | ||
| timestampBuffer: GPUBuffer | ||
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| // A buffer to map this result back to CPU | ||
| timestampMapBuffer: GPUBuffer | ||
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| // State used to avoid firing concurrent readback of timestamp values | ||
| hasOngoingTimestampReadback: boolean | ||
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| // Device must have the "timestamp-query" feature | ||
| constructor(device: GPUDevice, timestampCount: number) { | ||
| this.timestampSupported = device.features.has("timestamp-query"); | ||
| if (!this.timestampSupported) return; | ||
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| this.timestampCount = timestampCount; | ||
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| // Create timestamp queries | ||
| this.timestampQuerySet = device.createQuerySet({ | ||
| type: "timestamp", | ||
| count: timestampCount, // begin and end | ||
| }); | ||
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| // Create a buffer where to store the result of GPU queries | ||
| const timestampByteSize = 8; // timestamps are uint64 | ||
| const timestampBufferSize = timestampCount * timestampByteSize; | ||
| this.timestampBuffer = device.createBuffer({ | ||
| size: timestampBufferSize, | ||
| usage: GPUBufferUsage.COPY_SRC | GPUBufferUsage.QUERY_RESOLVE, | ||
| }); | ||
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| // Create a buffer to map the result back to the CPU | ||
| this.timestampMapBuffer = device.createBuffer({ | ||
| size: timestampBufferSize, | ||
| usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.MAP_READ, | ||
| }); | ||
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| this.hasOngoingTimestampReadback = false; | ||
| } | ||
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| // Resolve all timestamp queries and copy the result into the map buffer | ||
| resolveAll(commandEncoder: GPUCommandEncoder) { | ||
| if (!this.timestampSupported) return; | ||
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| // After the end of the measured render pass, we resolve queries into a | ||
| // dedicated buffer. | ||
| commandEncoder.resolveQuerySet( | ||
| this.timestampQuerySet, | ||
| 0 /* firstQuery */, | ||
| this.timestampCount /* queryCount */, | ||
| this.timestampBuffer, | ||
| 0, /* destinationOffset */ | ||
| ); | ||
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| if (!this.hasOngoingTimestampReadback) { | ||
| // Copy values to the mapped buffer | ||
| commandEncoder.copyBufferToBuffer( | ||
| this.timestampBuffer, 0, | ||
| this.timestampMapBuffer, 0, | ||
| this.timestampBuffer.size, | ||
| ); | ||
| } | ||
| } | ||
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| // Once resolved, we can read back the value of timestamps | ||
| readAsync(onTimestampReadBack: (timestamps: BigUint64Array) => void) { | ||
| if (!this.timestampSupported) return new Promise(() => {}); | ||
| if (this.hasOngoingTimestampReadback) return new Promise(() => {}); | ||
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| this.hasOngoingTimestampReadback = true; | ||
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| const buffer = this.timestampMapBuffer; | ||
| return new Promise(resolve => { | ||
| buffer.mapAsync(GPUMapMode.READ, 0, buffer.size) | ||
| .then(() => { | ||
| const rawData = buffer.getMappedRange(0, buffer.size); | ||
| const timestamps = new BigUint64Array(rawData); | ||
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| onTimestampReadBack(timestamps); | ||
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| buffer.unmap(); | ||
| this.hasOngoingTimestampReadback = false; | ||
| }) | ||
| }); | ||
| } | ||
| } |
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