MoltenVK timestamp doesn't report timing precisely

[PENGUINLIONG]

In the current implementation MoltenVK doesn't enforce a barrier when sampling a timestamp, in which case the timestamp may be sampled while some previous shaders are still running. As a result, the timings are totally unusable because they don't correctly represent the time spent on my dispatches. Is it possible to give it a YES to the withBarrier params?

MoltenVK/MoltenVK/MoltenVK/Commands/MVKCommandBuffer.mm

Lines 1004 to 1016 in bf097ed

	void MVKCommandEncoder::encodeGPUCounterSample(MVKGPUCounterQueryPool* mvkQryPool, uint32_t sampleIndex, MVKCounterSamplingFlags samplingPoints){
	if (_mtlRenderEncoder) {
	if (mvkIsAnyFlagEnabled(samplingPoints, MVK_COUNTER_SAMPLING_AT_DRAW)) {
	[_mtlRenderEncoder sampleCountersInBuffer: mvkQryPool->getMTLCounterBuffer() atSampleIndex: sampleIndex withBarrier: NO];
	}
	} else if (_mtlComputeEncoder) {
	if (mvkIsAnyFlagEnabled(samplingPoints, MVK_COUNTER_SAMPLING_AT_DISPATCH)) {
	[_mtlComputeEncoder sampleCountersInBuffer: mvkQryPool->getMTLCounterBuffer() atSampleIndex: sampleIndex withBarrier: NO];
	}
	} else if (mvkIsAnyFlagEnabled(samplingPoints, MVK_COUNTER_SAMPLING_AT_BLIT)) {
	[getMTLBlitEncoder(kMVKCommandUseRecordGPUCounterSample) sampleCountersInBuffer: mvkQryPool->getMTLCounterBuffer() atSampleIndex: sampleIndex withBarrier: NO];
	}
	}