Using GPUs for training models in the cloud

Graphics Processing Units (GPUs) can significantly accelerate the training process for many deep learning models. Training models for tasks like image classification, video analysis, and natural language processing involves compute-intensive matrix multiplication and other operations that can take advantage of a GPU's massively parallel architecture.

Training a deep learning model that involves intensive compute tasks on extremely large datasets can take days to run on a single processor. However, if you design your program to offload those tasks to one or more GPUs, you can reduce training time to hours instead of days.

Before you begin

AI Platform lets you run your TensorFlow training application on a GPU- enabled machine. Read the TensorFlow guide to using GPUs and the section below on assigning ops to GPUs to ensure your application makes use of available GPUs.

You can also use GPUs with machine learning frameworks other than TensorFlow, if you use a custom container for training.

Some models don't benefit from running on GPUs. We recommend GPUs for large, complex models that have many mathematical operations. Even then, you should test the benefit of GPU support by running a small sample of your data through training.

Requesting GPU-enabled machines

To use GPUs in the cloud, configure your training job to access GPU-enabled machines in one of three ways: Use the BASIC_GPU scale tier, use GPU-enabled AI Platform machine types, or use Compute Engine machine types and attach GPUs.

Basic GPU-enabled machine

If you are learning how to use AI Platform or experimenting with GPU-enabled machines, you can set the scale tier to BASIC_GPU to get a single worker instance with a single NVIDIA Tesla K80 GPU.

Machine types with GPUs included

To customize your GPU usage, configure your training job with GPU-enabled machine types:

  • Set the scale tier to CUSTOM.
  • Configure each worker type (master, worker, or parameter server) to use one of the GPU-enabled machine types below, based on the number of GPUs and the type of accelerator required for your task:
    • standard_gpu: A single NVIDIA Tesla K80 GPU
    • complex_model_m_gpu: Four NVIDIA Tesla K80 GPUs
    • complex_model_l_gpu: Eight NVIDIA Tesla K80 GPUs
    • standard_p100: A single NVIDIA Tesla P100 GPU
    • complex_model_m_p100: Four NVIDIA Tesla P100 GPUs
    • standard_v100: A single NVIDIA Tesla V100 GPU
    • large_model_v100: A single NVIDIA Tesla V100 GPU
    • complex_model_m_v100: Four NVIDIA Tesla V100 GPUs
    • complex_model_l_v100: Eight NVIDIA Tesla V100 GPUs

Below is an example of submitting a job with GPU-enabled machine types using the gcloud command.

See more information about comparing machine types.

Compute Engine machine types with GPU attachments

Alternatively, if you configure your training job with Compute Engine machine types, which do not include GPUs by default, you can attach a custom number of GPUs to accelerate your job:

  • Set the scale tier to CUSTOM.
  • Configure each worker type (master, worker, or parameter server) to use a valid Compute Engine machine type.
  • Add an acceleratorConfig field with the type and number of GPUs you want to masterConfig, workerConfig, or parameterServerConfig, depending on which virtual machines you would like to accelerate. You can use the following GPU types:
    • NVIDIA_TESLA_K80
    • NVIDIA_TESLA_P4
    • NVIDIA_TESLA_P100
    • NVIDIA_TESLA_T4
    • NVIDIA_TESLA_V100

To create a valid acceleratorConfig, you must account for several restrictions:

  1. You can only use certain numbers of GPUs in your configuration. For example, you can attach 2 or 4 NVIDIA Tesla K80s, but not 3. To see what counts are valid for each type of GPU, see the compatibility table below.

  2. You must make sure each of your GPU configurations provides sufficient virtual CPUs and memory to the machine type you attach it to. For example, if you use n1-standard-32 for your workers, then each worker has 32 virtual CPUs and 120 GB of memory. Since each NVIDIA Tesla V100 can provide up to 8 virtual CPUs and 52 GB of memory, you must attach at least 4 to each n1-standard-32 worker to support its requirements.

    Review the table of machine type specifications and the comparison of GPUs for compute workloads to determine these compatibilities, or reference the compatibility table below.

    Note the following additional limitations on GPU resources for AI Platform in particular cases:

    • A configuration with 8 NVIDIA Tesla K80 GPUs only provides up to 208 GB of memory in all regions and zones.
    • A configuration with 4 NVIDIA Tesla P100 GPUs only supports up to 64 virtual CPUS and up to 208 GB of memory in all regions and zones.
  3. You must submit your training job to a region that supports your GPU configuration. Read about region support below.

The following table provides a quick reference of how many of each type of accelerator you can attach to each Compute Engine machine type:

Valid numbers of GPUs for each machine type
Machine type NVIDIA Tesla K80 NVIDIA Tesla P4 NVIDIA Tesla P100 NVIDIA Telsa T4 NVIDIA Tesla V100
n1-standard-4 1, 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 1, 2, 4, 8
n1-standard-8 1, 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 1, 2, 4, 8
n1-standard-16 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 2, 4, 8
n1-standard-32 4, 8 2, 4 2, 4 2, 4 4, 8
n1-standard-64 4 4 8
n1-standard-96 4 4 8
n1-highmem-2 1, 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 1, 2, 4, 8
n1-highmem-4 1, 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 1, 2, 4, 8
n1-highmem-8 1, 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 1, 2, 4, 8
n1-highmem-16 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 2, 4, 8
n1-highmem-32 4, 8 2, 4 2, 4 2, 4 4, 8
n1-highmem-64 4 4 8
n1-highmem-96 4 4 8
n1-highcpu-16 2, 4, 8 1, 2, 4 1, 2, 4 1, 2, 4 2, 4, 8
n1-highcpu-32 4, 8 2, 4 2, 4 2, 4 4, 8
n1-highcpu-64 8 4 4 4 8
n1-highcpu-96 4 4 8

Below is an example of submitting a job using Compute Engine machine types with GPUs attached.

Regions that support GPUs

You must run your job in a region that supports GPUs. The following regions currently provide access to GPUs:

  • us-west1
  • us-central1
  • us-east1
  • europe-west1
  • europe-west4
  • asia-southeast1
  • asia-east1

In addition, some of these regions only provide access to certain types of GPUs. To fully understand the available regions for AI Platform services, including model training and online/batch prediction, read the guide to regions.

If your training job uses multiple types of GPUs, they must all be available in a single zone in your region. For example, you cannot run a job in us-central1 with a master worker using NVIDIA Tesla V100 GPUs, parameter servers using NVIDIA Tesla K80 GPUs, and workers using NVIDIA Tesla P100 GPUs. While all of these GPUs are available for training jobs in us-central1, no single zone in that region provides all three types of GPU. To learn more about the zone availability of GPUs, see the comparison of GPUs for compute workloads.

Submitting the training job

You can submit your training job using the gcloud ai-platform jobs submit training command.

  1. Define a config.yaml file that describes the GPU options you want. The structure of the YAML file represents the Job resource. Below are two examples of config.yaml files.

    The first example shows a configuration file for a training job using AI Platform machine types, some of which include GPUs:

    trainingInput:
      scaleTier: CUSTOM
      # Configure a master worker with 4 K80 GPUs
      masterType: complex_model_m_gpu
      # Configure 9 workers, each with 4 K80 GPUs
      workerCount: 9
      workerType: complex_model_m_gpu
      # Configure 3 parameter servers with no GPUs
      parameterServerCount: 3
      parameterServerType: large_model
    

    The next example shows a configuration file for a job with a similar configuration as the one above. However, this configuration uses Compute Engine machine types with GPUs attached:

    trainingInput:
      scaleTier: CUSTOM
      # Configure a master worker with 4 K80 GPUs
      masterType: n1-highcpu-16
      masterConfig:
        acceleratorConfig:
          count: 4
          type: NVIDIA_TESLA_K80
      # Configure 9 workers, each with 4 K80 GPUs
      workerCount: 9
      workerType: n1-highcpu-16
      workerConfig:
        acceleratorConfig:
          count: 4
          type: NVIDIA_TESLA_K80
      # Configure 3 parameter servers with no GPUs
      parameterServerCount: 3
      parameterServerType: n1-highmem-8
    
  2. Use the gcloud command to submit the job, including a --config argument pointing to your config.yaml file. The following example assumes you've set up environment variables, indicated by a $ sign followed by capital letters, for the values of some arguments:

    gcloud ai-platform jobs submit training $JOB_NAME \
            --package-path $APP_PACKAGE_PATH \
            --module-name $MAIN_APP_MODULE \
            --job-dir $JOB_DIR \
            --region us-central1 \
            --config config.yaml \
            -- \
            --user_arg_1 value_1 \
             ...
            --user_arg_n value_n
    

Alternatively, you may specify cluster configuration details with command-line flags, rather than in a configuration file. Learn more about how to use these flags.

The following example shows how to submit a job with the same configuration as the previous example (using Compute Engine machine types with GPUs attached), but it does so without using a config.yaml file:

gcloud ai-platform jobs submit training $JOB_NAME \
        --package-path $APP_PACKAGE_PATH \
        --module-name $MAIN_APP_MODULE \
        --job-dir $JOB_DIR \
        --region us-central1 \
        --scale-tier custom \
        --master-machine-type n1-highcpu-16 \
        --master-accelerator count=4,type=nvidia-tesla-k80 \
        --worker-server-count 9 \
        --worker-machine-type n1-highcpu-16 \
        --worker-accelerator count=4,type=nvidia-tesla-k80 \
        --parameter-server-count 3 \
        --parameter-server-machine-type n1-highmem-8 \
        -- \
        --user_arg_1 value_1 \
         ...
        --user_arg_n value_n

Notes:

  • If you specify an option both in your configuration file (config.yaml) and as a command-line flag, the value on the command line overrides the value in the configuration file.
  • The empty -- flag marks the end of the gcloud specific flags and the start of the USER_ARGS that you want to pass to your application.
  • Flags specific to AI Platform, such as --module-name, --runtime-version, and --job-dir, must come before the empty -- flag. The AI Platform service interprets these flags.
  • The --job-dir flag, if specified, must come before the empty -- flag, because AI Platform uses the --job-dir to validate the path.
  • Your application must handle the --job-dir flag too, if specified. Even though the flag comes before the empty --, the --job-dir is also passed to your application as a command-line flag.
  • You can define as many USER_ARGS as you need. AI Platform passes --user_first_arg, --user_second_arg, and so on, through to your application.

For more details of the job submission options, see the guide to starting a training job.

Assigning ops to GPUs

To make use of the GPUs on a machine, make the appropriate changes to your TensorFlow training application:

  • High-level Estimator API: No code changes are necessary as long as your ClusterSpec is configured properly. If a cluster is a mixture of CPUs and GPUs, map the ps job name to the CPUs and the worker job name to the GPUs.

  • Core TensorFlow API: You must assign ops to run on GPU-enabled machines. This process is the same as using GPUs with TensorFlow locally. You can use tf.train.replica_device_setter to assign ops to devices.

When you assign a GPU-enabled machine to an AI Platform process, that process has exclusive access to that machine's GPUs; you can't share the GPUs of a single machine in your cluster among multiple processes. The process corresponds to the distributed TensorFlow task in your cluster specification. The distributed TensorFlow documentation describes cluster specifications and tasks.

GPU device strings

A standard_gpu machine's single GPU is identified as "/gpu:0". Machines with multiple GPUs use identifiers starting with "/gpu:0", then "/gpu:1", and so on. For example, complex_model_m_gpu machines have four GPUs identified as "/gpu:0" through "/gpu:3".

Python packages on GPU-enabled machines

GPU-enabled machines come pre-installed with tensorflow-gpu, the TensorFlow Python package with GPU support. See the Cloud ML Runtime Version List for a list of all pre-installed packages.

Maintenance events

If you use GPUs in your training jobs, be aware that the underlying virtual machines will occasionally be subject to Compute Engine host maintenance. The GPU-enabled virtual machines used in your training jobs are configured to automatically restart after such maintenance events, but you may have to do some extra work to ensure that your job is resilient to these shutdowns. Configure your training application to regularly save model checkpoints (usually along the Cloud Storage path you specify through the --job-dir argument to gcloud ai-platform jobs submit training) and to restore the most recent checkpoint in the case that a checkpoint already exists.

The TensorFlow Estimator API implements this functionality for you, so if your model is already wrapped in an Estimator, you do not have to worry about maintenance events on your GPU workers.

If it is not feasible for you to wrap your model in a TensorFlow Estimator and you want your GPU-enabled training jobs to be resilient to maintenance events, you must write the checkpoint saving and restoration functionality into your model manually. TensorFlow does provide some useful resources for such an implementation in the tf.train module - specifically, tf.train.checkpoint_exists and tf.train.latest_checkpoint.

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