You’re Wasting GPU Power—Fix Your TensorFlow Input Pipeline Today

Content Overview Overview Resources Setup The dataset The training loop Optimize approach The naive approach Prefetching Parallelizing data extraction Parallelizing data transformation Caching Vectorizing mapping Reducing memory footprint Overview Resources Setup The dataset The training loop Optimize approach The naive approach Prefetching Parallelizing data extraction Parallelizing data transformation Caching Vectorizing mapping Reducing memory footprint Overview GPUs and TPUs can radically reduce the time required to execute a single training step. Achieving peak performance requires an efficient input pipeline that delivers data for the next step before the current step has finished. The tf.data API helps to build flexible and efficient input pipelines. This document demonstrates how to use the tf.data API to build highly performant TensorFlow input pipelines. tf.data tf.data Before you continue, check the Build TensorFlow input pipelines guide to learn how to use the tf.data API. Build TensorFlow input pipelines tf.data Resources Build TensorFlow input pipelines tf.data.Dataset API Analyze tf.data performance with the TF Profiler Build TensorFlow input pipelines tf.data.Dataset API tf.data.Dataset Analyze tf.data performance with the TF Profiler Analyze tf.data Setup import tensorflow as tf import time import tensorflow as tf import time 2024-08-15 02:29:59.860833: E external/local_xla/xla/stream_executor/cuda/cuda_fft.cc:485] Unable to register cuFFT factory: Attempting to register factory for plugin cuFFT when one has already been registered 2024-08-15 02:29:59.882136: E external/local_xla/xla/stream_executor/cuda/cuda_dnn.cc:8454] Unable to register cuDNN factory: Attempting to register factory for plugin cuDNN when one has already been registered 2024-08-15 02:29:59.888640: E external/local_xla/xla/stream_executor/cuda/cuda_blas.cc:1452] Unable to register cuBLAS factory: Attempting to register factory for plugin cuBLAS when one has already been registered 2024-08-15 02:29:59.860833: E external/local_xla/xla/stream_executor/cuda/cuda_fft.cc:485] Unable to register cuFFT factory: Attempting to register factory for plugin cuFFT when one has already been registered 2024-08-15 02:29:59.882136: E external/local_xla/xla/stream_executor/cuda/cuda_dnn.cc:8454] Unable to register cuDNN factory: Attempting to register factory for plugin cuDNN when one has already been registered 2024-08-15 02:29:59.888640: E external/local_xla/xla/stream_executor/cuda/cuda_blas.cc:1452] Unable to register cuBLAS factory: Attempting to register factory for plugin cuBLAS when one has already been registered Throughout this guide, you will iterate across a dataset and measure the performance. Making reproducible performance benchmarks can be difficult. Different factors affecting reproducibility include: The current CPU load The network traffic Complex mechanisms, such as cache The current CPU load The network traffic Complex mechanisms, such as cache To get a reproducible benchmark, you will build an artificial example. The dataset Start with defining a class inheriting from tf.data.Dataset called ArtificialDataset. This dataset: tf.data.Dataset ArtificialDataset Generates num_samples samples (default is 3) Sleeps for some time before the first item to simulate opening a file Sleeps for some time before producing each item to simulate reading data from a file Generates num_samples samples (default is 3) num_samples Sleeps for some time before the first item to simulate opening a file Sleeps for some time before producing each item to simulate reading data from a file class ArtificialDataset(tf.data.Dataset): def _generator(num_samples): # Opening the file time.sleep(0.03) for sample_idx in range(num_samples): # Reading data (line, record) from the file time.sleep(0.015) yield (sample_idx,) def __new__(cls, num_samples=3): return tf.data.Dataset.from_generator( cls._generator, output_signature = tf.TensorSpec(shape = (1,), dtype = tf.int64), args=(num_samples,) ) class ArtificialDataset(tf.data.Dataset): def _generator(num_samples): # Opening the file time.sleep(0.03) for sample_idx in range(num_samples): # Reading data (line, record) from the file time.sleep(0.015) yield (sample_idx,) def __new__(cls, num_samples=3): return tf.data.Dataset.from_generator( cls._generator, output_signature = tf.TensorSpec(shape = (1,), dtype = tf.int64), args=(num_samples,) ) This dataset is similar to the tf.data.Dataset.range one, adding a fixed delay at the beginning of and in-between each sample. tf.data.Dataset.range The training loop Next, write a dummy training loop that measures how long it takes to iterate over a dataset. Training time is simulated. def benchmark(dataset, num_epochs=2): start_time = time.perf_counter() for epoch_num in range(num_epochs): for sample in dataset: # Performing a training step time.sleep(0.01) print("Execution time:", time.perf_counter() - start_time) def benchmark(dataset, num_epochs=2): start_time = time.perf_counter() for epoch_num in range(num_epochs): for sample in dataset: # Performing a training step time.sleep(0.01) print("Execution time:", time.perf_counter() - start_time) Optimize performance To exhibit how performance can be optimized, you will improve the performance of the ArtificialDataset. ArtificialDataset The naive approach Start with a naive pipeline using no tricks, iterating over the dataset as-is. benchmark(ArtificialDataset()) benchmark(ArtificialDataset()) WARNING: All log messages before absl::InitializeLog() is called are written to STDERR I0000 00:00:1723689002.526086 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.529717 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.533395 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.537215 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.548874 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.552105 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.555507 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.559016 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.562268 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.565421 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.568842 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.572296 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.797478 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.799457 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.801473 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.803565 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.805613 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.807466 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.809382 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.811373 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.813299 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.815122 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.817022 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.819005 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.857728 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.860099 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.862063 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.864094 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.866073 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.867912 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.869940 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.871942 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.873924 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.876256 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.878556 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.880974 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 Execution time: 0.28992818999995507 WARNING: All log messages before absl::InitializeLog() is called are written to STDERR I0000 00:00:1723689002.526086 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.529717 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.533395 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.537215 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.548874 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.552105 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.555507 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.559016 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.562268 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.565421 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.568842 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689002.572296 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.797478 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.799457 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.801473 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.803565 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.805613 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.807466 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.809382 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.811373 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.813299 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.815122 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.817022 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.819005 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.857728 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.860099 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.862063 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.864094 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.866073 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.867912 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.869940 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.871942 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.873924 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.876256 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.878556 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 I0000 00:00:1723689003.880974 112933 cuda_executor.cc:1015] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero. See more at https://github.com/torvalds/linux/blob/v6.0/Documentation/ABI/testing/sysfs-bus-pci#L344-L355 Execution time: 0.28992818999995507 Under the hood, this is how your execution time was spent: The plot shows that performing a training step involves: Opening a file if it hasn't been opened yet Fetching a data entry from the file Using the data for training Opening a file if it hasn't been opened yet Fetching a data entry from the file Using the data for training However, in a naive synchronous implementation like here, while your pipeline is fetching the data, your model is sitting idle. Conversely, while your model is training, the input pipeline is sitting idle. The training step time is thus the sum of opening, reading and training times. The next sections build on this input pipeline, illustrating best practices for designing performant TensorFlow input pipelines. Prefetching Prefetching overlaps the preprocessing and model execution of a training step. While the model is executing training step s, the input pipeline is reading the data for step s+1. Doing so reduces the step time to the maximum (as opposed to the sum) of the training and the time it takes to extract the data. s s+1 The tf.data API provides the tf.data.Dataset.prefetch transformation. It can be used to decouple the time when data is produced from the time when data is consumed. In particular, the transformation uses a background thread and an internal buffer to prefetch elements from the input dataset ahead of the time they are requested. The number of elements to prefetch should be equal to (or possibly greater than) the number of batches consumed by a single training step. You could either manually tune this value, or set it to tf.data.AUTOTUNE, which will prompt the tf.data runtime to tune the value dynamically at runtime. tf.data tf.data.Dataset.prefetch tf.data.AUTOTUNE tf.data Note that the prefetch transformation provides benefits any time there is an opportunity to overlap the work of a "producer" with the work of a "consumer." benchmark( ArtificialDataset() .prefetch(tf.data.AUTOTUNE) ) benchmark( ArtificialDataset() .prefetch(tf.data.AUTOTUNE) ) Execution time: 0.282483695999872 Execution time: 0.282483695999872 Now, as the data execution time plot shows, while the training step is running for sample 0, the input pipeline is reading the data for the sample 1, and so on. Parallelizing data extraction In a real-world setting, the input data may be stored remotely (for example, on Google Cloud Storage or HDFS). A dataset pipeline that works well when reading data locally might become bottlenecked on I/O when reading data remotely because of the following differences between local and remote storage: Time-to-first-byte: Reading the first byte of a file from remote storage can take orders of magnitude longer than from local storage. Read throughput: While remote storage typically offers large aggregate bandwidth, reading a single file might only be able to utilize a small fraction of this bandwidth. Time-to-first-byte: Reading the first byte of a file from remote storage can take orders of magnitude longer than from local storage. Time-to-first-byte Read throughput: While remote storage typically offers large aggregate bandwidth, reading a single file might only be able to utilize a small fraction of this bandwidth. Read throughput In addition, once the raw bytes are loaded into memory, it may also be necessary to deserialize and/or decrypt the data (e.g. protobuf), which requires additional computation. This overhead is present irrespective of whether the data is stored locally or remotely, but can be worse in the remote case if data is not prefetched effectively. protobuf To mitigate the impact of the various data extraction overheads, the tf.data.Dataset.interleave transformation can be used to parallelize the data loading step, interleaving the contents of other datasets (such as data file readers). The number of datasets to overlap can be specified by the cycle_length argument, while the level of parallelism can be specified by the num_parallel_calls argument. Similar to the prefetch transformation, the interleave transformation supports tf.data.AUTOTUNE, which will delegate the decision about what level of parallelism to use to the tf.data runtime. tf.data.Dataset.interleave cycle_length num_parallel_calls prefetch interleave tf.data.AUTOTUNE tf.data Sequential interleave The default arguments of the tf.data.Dataset.interleave transformation make it interleave single samples from two datasets sequentially. tf.data.Dataset.interleave benchmark( tf.data.Dataset.range(2) .interleave(lambda _: ArtificialDataset()) ) benchmark( tf.data.Dataset.range(2) .interleave(lambda _: ArtificialDataset()) ) Execution time: 0.4770545540004605 Execution time: 0.4770545540004605 This data execution time plot allows to exhibit the behavior of the interleave transformation, fetching samples alternatively from the two datasets available. However, no performance improvement is involved here. interleave Parallel interleave Now, use the num_parallel_calls argument of the interleave transformation. This loads multiple datasets in parallel, reducing the time waiting for the files to be opened. num_parallel_calls interleave benchmark( tf.data.Dataset.range(2) .interleave( lambda _: ArtificialDataset(), num_parallel_calls=tf.data.AUTOTUNE ) ) benchmark( tf.data.Dataset.range(2) .interleave( lambda _: ArtificialDataset(), num_parallel_calls=tf.data.AUTOTUNE ) ) Execution time: 0.37743708600009995 Execution time: 0.37743708600009995 This time, as the data execution time plot shows, the reading of the two datasets is parallelized, reducing the global data processing time. Parallelizing data transformation When preparing data, input elements may need to be pre-processed. To this end, the tf.data API offers the tf.data.Dataset.map transformation, which applies a user-defined function to each element of the input dataset. Because input elements are independent of one another, the pre-processing can be parallelized across multiple CPU cores. To make this possible, similarly to the prefetch and interleave transformations, the map transformation provides the num_parallel_calls argument to specify the level of parallelism. tf.data tf.data.Dataset.map prefetch interleave map num_parallel_calls Choosing the best value for the num_parallel_calls argument depends on your hardware, characteristics of your training data (such as its size and shape), the cost of your map function, and what other processing is happening on the CPU at the same time. A simple heuristic is to use the number of available CPU cores. However, as for the prefetch and interleave transformation, the map transformation supports tf.data.AUTOTUNE which will delegate the decision about what level of parallelism to use to the tf.data runtime. num_parallel_calls prefetch interleave map tf.data.AUTOTUNE tf.data def mapped_function(s): # Do some hard pre-processing tf.py_function(lambda: time.sleep(0.03), [], ()) return s def mapped_function(s): # Do some hard pre-processing tf.py_function(lambda: time.sleep(0.03), [], ()) return s Sequential mapping Start by using the map transformation without parallelism as a baseline example. map benchmark( ArtificialDataset() .map(mapped_function) ) benchmark( ArtificialDataset() .map(mapped_function) ) Execution time: 0.49222556600034295 Execution time: 0.49222556600034295 As for the naive approach, here, as the plot shows, the times spent for opening, reading, pre-processing (mapping) and training steps sum together for a single iteration. naive approach Parallel mapping Now, use the same pre-processing function but apply it in parallel on multiple samples. benchmark( ArtificialDataset() .map( mapped_function, num_parallel_calls=tf.data.AUTOTUNE ) ) benchmark( ArtificialDataset() .map( mapped_function, num_parallel_calls=tf.data.AUTOTUNE ) ) Execution time: 0.36392719900049997 Execution time: 0.36392719900049997 As the data plot demonstrates, the pre-processing steps overlap, reducing the overall time for a single iteration. Caching The tf.data.Dataset.cache transformation can cache a dataset, either in memory or on local storage. This will save some operations (like file opening and data reading) from being executed during each epoch. tf.data.Dataset.cache benchmark( ArtificialDataset() .map( # Apply time consuming operations before cache mapped_function ).cache( ), 5 ) benchmark( ArtificialDataset() .map( # Apply time consuming operations before cache mapped_function ).cache( ), 5 ) Execution time: 0.3864543270001377 Execution time: 0.3864543270001377 Here, the data execution time plot shows that when you cache a dataset, the transformations before the cache one (like the file opening and data reading) are executed only during the first epoch. The next epochs will reuse the data cached by thecache transformation. cache cache If the user-defined function passed into the map transformation is expensive, apply the cache transformation after the map transformation as long as the resulting dataset can still fit into memory or local storage. If the user-defined function increases the space required to store the dataset beyond the cache capacity, either apply it after the cache transformation or consider pre-processing your data before your training job to reduce resource usage. map cache map cache Vectorizing mapping Invoking a user-defined function passed into the map transformation has overhead related to scheduling and executing the user-defined function. Vectorize the user-defined function (that is, have it operate over a batch of inputs at once) and apply the batch transformation before the map transformation. map batch before map To illustrate this good practice, your artificial dataset is not suitable. The scheduling delay is around 10 microseconds (10e-6 seconds), far less than the tens of milliseconds used in the ArtificialDataset, and thus its impact is hard to see. ArtificialDataset For this example, use the base tf.data.Dataset.range function and simplify the training loop to its simplest form. tf.data.Dataset.range fast_dataset = tf.data.Dataset.range(10000) def fast_benchmark(dataset, num_epochs=2): start_time = time.perf_counter() for _ in tf.data.Dataset.range(num_epochs): for _ in dataset: pass tf.print("Execution time:", time.perf_counter() - start_time) def increment(x): return x+1 fast_dataset = tf.data.Dataset.range(10000) def fast_benchmark(dataset, num_epochs=2): start_time = time.perf_counter() for _ in tf.data.Dataset.range(num_epochs): for _ in dataset: pass tf.print("Execution time:", time.perf_counter() - start_time) def increment(x): return x+1 Scalar mapping fast_benchmark( fast_dataset # Apply function one item at a time .map(increment) # Batch .batch(256) ) fast_benchmark( fast_dataset # Apply function one item at a time .map(increment) # Batch .batch(256) ) Execution time: 0.23993100699954084 Execution time: 0.23993100699954084 The plot above illustrates what is going on (with less samples) using the scalar mapping method. It shows that the mapped function is applied for each sample. While this function is very fast, it has some overhead that impact the time performance. Vectorized mapping fast_benchmark( fast_dataset .batch(256) # Apply function on a batch of items # The tf.Tensor.__add__ method already handle batches .map(increment) ) fast_benchmark( fast_dataset .batch(256) # Apply function on a batch of items # The tf.Tensor.__add__ method already handle batches .map(increment) ) Execution time: 0.04984995199993136 Execution time: 0.04984995199993136 This time, the mapped function is called once and applies to a batch of sample. As the data execution time plot shows, while the function could takes more time to execute, the overhead appear only once, improving the overall time performance. Reducing memory footprint A number of transformations, including interleave, prefetch, and shuffle, maintain an internal buffer of elements. If the user-defined function passed into the map transformation changes the size of the elements, then the ordering of the map transformation and the transformations that buffer elements affects the memory usage. In general, choose the order that results in lower memory footprint, unless different ordering is desirable for performance. interleave prefetch shuffle map Caching partial computations It is recommended to cache the dataset after the map transformation except if this transformation makes the data too big to fit in memory. A trade-off can be achieved if your mapped function can be split in two parts: a time consuming one and a memory consuming part. In this case, you can chain your transformations like below: map dataset.map(time_consuming_mapping).cache().map(memory_consuming_mapping) dataset.map(time_consuming_mapping).cache().map(memory_consuming_mapping) This way, the time consuming part is only executed during the first epoch, and you avoid using too much cache space. Originally published on the TensorFlow website, this article appears here under a new headline and is licensed under CC BY 4.0. Code samples shared under the Apache 2.0 License. Originally published on the TensorFlow website, this article appears here under a new headline and is licensed under CC BY 4.0. Code samples shared under the Apache 2.0 License. Originally published on the TensorFlow website, this article appears here under a new headline and is licensed under CC BY 4.0. Code samples shared under the Apache 2.0 License. TensorFlow TensorFlow