ACK基于Scheduling Framework机制，实现GPU拓扑感知调度，即在节点的GPU组合中选择具有最优训练速度的组合。本文主要介绍如何使用GPU拓扑感知调度来提升Pytorch分布式训练的训练速度。

前提条件

  • 创建ACK Pro版集群。
  • 安装Arena。
  • 安装GPU拓扑感知组件。
  • 系统组件版本要求具体如下表所示。
    组件 版本要求
    Kubernetes 1.18.8及以上版本
    Helm 3.0及以上版本
    Nvidia 418.87.01及以上版本
    训练框架NCCL版本 2.7+
    Docker 19.03.5
    操作系统 CentOS 7.6、CentOS 7.7、Ubuntu 16.04和Ubuntu 18.04、Alibaba Cloud Linux 2
    显卡 V100

应用限制

  • 仅支持MPI作业的分布式训练。
  • 只有当提交作业的所有Pod对资源请求都满足条件时，才能创建Pod并启动作业，否则请求会处于资源等待状态。

操作步骤

节点配置

您需执行以下命令设置节点Label，显式激活节点GPU拓扑感知调度。
kubectl label node <Your Node Name> ack.node.gpu.schedule=topology
说明 当节点激活GPU拓扑感知调度后，不再支持普通GPU资源调度。可执行以下命令更改Label，恢复普通GPU资源调度功能。
kubectl label node <Your Node Name> ack.node.gpu.schedule=default --overwrite

提交作业

您在提交MPI作业时，执行以下命令设置--gputopology为true。 

arena submit mpi --gputopology=true ***

示例一：训练Vgg16

说明 本文测试集群有2台8卡V100机器。

使用GPU拓扑感知调度训练Vgg16

  1. 使用以下命令向集群提交作业。
    arena submit mpi \
  --name=pytorch-topo-4-vgg16 \
  --gpus=1 \
  --workers=4 \
  --gputopology=true \
  --image=registry.cn-hangzhou.aliyuncs.com/kubernetes-image-hub/pytorch-benchmark:torch1.6.0-py3.7-cuda10.1 \
  "mpirun --allow-run-as-root -np "4" -bind-to none -map-by slot -x NCCL_DEBUG=INFO -x NCCL_SOCKET_IFNAME=eth0 -x LD_LIBRARY_PATH -x PATH --mca pml ob1 --mca btl_tcp_if_include eth0 --mca oob_tcp_if_include eth0 --mca orte_keep_fqdn_hostnames t --mca btl ^openib python /examples/pytorch_synthetic_benchmark.py --model=vgg16 --batch-size=64"
  2. 执行以下命令，查看当前作业运行情况。
    arena get pytorch-topo-4-vgg16 --type mpijob

    预期输出：

    Name:      pytorch-topo-4-vgg16
Status:    RUNNING
Namespace: default
Priority:  N/A
Trainer:   MPIJOB
Duration:  11s

Instances:
  NAME                                 STATUS   AGE  IS_CHIEF  GPU(Requested)  NODE
  ----                                 ------   ---  --------  --------------  ----
  pytorch-topo-4-vgg16-launcher-mnjzr  Running  11s  true      0               cn-shanghai.192.168.16.173
  pytorch-topo-4-vgg16-worker-0        Running  11s  false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-vgg16-worker-1        Running  11s  false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-vgg16-worker-2        Running  11s  false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-vgg16-worker-3        Running  11s  false     1               cn-shanghai.192.168.16.173
  3. 执行以下命令，查看当前日志信息。
    arena logs -f pytorch-topo-4-vgg16

    预期输出：

    Model: vgg16
Batch size: 64
Number of GPUs: 4
Running warmup...
Running benchmark...
Iter #0: 205.5 img/sec per GPU
Iter #1: 205.2 img/sec per GPU
Iter #2: 205.1 img/sec per GPU
Iter #3: 205.5 img/sec per GPU
Iter #4: 205.1 img/sec per GPU
Iter #5: 205.1 img/sec per GPU
Iter #6: 205.3 img/sec per GPU
Iter #7: 204.3 img/sec per GPU
Iter #8: 205.0 img/sec per GPU
Iter #9: 204.9 img/sec per GPU
Img/sec per GPU: 205.1 +-0.6
Total img/sec on 4 GPU(s): 820.5 +-2.5

使用普通GPU调度训练Vgg16

  1. 使用以下命令向集群提交作业。
    arena submit mpi \
  --name=pytorch-4-vgg16 \
  --gpus=1 \
  --workers=4 \
  --image=registry.cn-hangzhou.aliyuncs.com/kubernetes-image-hub/pytorch-benchmark:torch1.6.0-py3.7-cuda10.1 \
  "mpirun --allow-run-as-root -np "4" -bind-to none -map-by slot -x NCCL_DEBUG=INFO -x NCCL_SOCKET_IFNAME=eth0 -x LD_LIBRARY_PATH -x PATH --mca pml ob1 --mca btl_tcp_if_include eth0 --mca oob_tcp_if_include eth0 --mca orte_keep_fqdn_hostnames t --mca btl ^openib python /examples/pytorch_synthetic_benchmark.py --model=vgg16 --batch-size=64"
  2. 执行以下命令，查看当前作业运行情况。
    arena get pytorch-4-vgg16 --type mpijob

    预期输出：

    Name:      pytorch-4-vgg16
Status:    RUNNING
Namespace: default
Priority:  N/A
Trainer:   MPIJOB
Duration:  10s

Instances:
  NAME                            STATUS   AGE  IS_CHIEF  GPU(Requested)  NODE
  ----                            ------   ---  --------  --------------  ----
  pytorch-4-vgg16-launcher-qhnxl  Running  10s  true      0               cn-shanghai.192.168.16.173
  pytorch-4-vgg16-worker-0        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-vgg16-worker-1        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-vgg16-worker-2        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-vgg16-worker-3        Running  10s  false     1               cn-shanghai.192.168.16.173
  3. 执行以下命令，查看当前日志信息。
    arena logs -f pytorch-4-vgg16

    预期输出：

    Model: vgg16
Batch size: 64
Number of GPUs: 4
Running warmup...
Running benchmark...
Iter #0: 113.1 img/sec per GPU
Iter #1: 109.5 img/sec per GPU
Iter #2: 106.5 img/sec per GPU
Iter #3: 108.5 img/sec per GPU
Iter #4: 108.1 img/sec per GPU
Iter #5: 111.2 img/sec per GPU
Iter #6: 110.7 img/sec per GPU
Iter #7: 109.8 img/sec per GPU
Iter #8: 102.8 img/sec per GPU
Iter #9: 107.9 img/sec per GPU
Img/sec per GPU: 108.8 +-5.3
Total img/sec on 4 GPU(s): 435.2 +-21.1

示例二：训练Resnet50

使用GPU拓扑感知调度训练Resnet50

  1. 使用以下命令向集群提交作业。
    arena submit mpi \
  --name=pytorch-topo-4-resnet50 \
  --gpus=1 \
  --workers=4 \
  --gputopology=true \
  --image=registry.cn-hangzhou.aliyuncs.com/kubernetes-image-hub/pytorch-benchmark:torch1.6.0-py3.7-cuda10.1 \
  "mpirun --allow-run-as-root -np "4" -bind-to none -map-by slot -x NCCL_DEBUG=INFO -x NCCL_SOCKET_IFNAME=eth0 -x LD_LIBRARY_PATH -x PATH --mca pml ob1 --mca btl_tcp_if_include eth0 --mca oob_tcp_if_include eth0 --mca orte_keep_fqdn_hostnames t --mca btl ^openib python /examples/pytorch_synthetic_benchmark.py --model=resnet50 --batch-size=64"
  2. 执行以下命令，查看当前作业运行情况。
    arena get pytorch-topo-4-resnet50 --type mpijob

    预期输出：

    Name:      pytorch-topo-4-resnet50
Status:    RUNNING
Namespace: default
Priority:  N/A
Trainer:   MPIJOB
Duration:  8s

Instances:
  NAME                                    STATUS   AGE  IS_CHIEF  GPU(Requested)  NODE
  ----                                    ------   ---  --------  --------------  ----
  pytorch-topo-4-resnet50-launcher-x7r2n  Running  8s   true      0               cn-shanghai.192.168.16.173
  pytorch-topo-4-resnet50-worker-0        Running  8s   false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-resnet50-worker-1        Running  8s   false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-resnet50-worker-2        Running  8s   false     1               cn-shanghai.192.168.16.173
  pytorch-topo-4-resnet50-worker-3        Running  8s   false     1               cn-shanghai.192.168.16.173
  3. 执行以下命令，查看当前日志信息。
    arena logs -f pytorch-topo-4-resnet50

    预期输出：

    Model: resnet50
Batch size: 64
Number of GPUs: 4
Running warmup...
Running benchmark...
Iter #0: 331.0 img/sec per GPU
Iter #1: 330.6 img/sec per GPU
Iter #2: 330.9 img/sec per GPU
Iter #3: 330.4 img/sec per GPU
Iter #4: 330.7 img/sec per GPU
Iter #5: 330.8 img/sec per GPU
Iter #6: 329.9 img/sec per GPU
Iter #7: 330.5 img/sec per GPU
Iter #8: 330.4 img/sec per GPU
Iter #9: 329.7 img/sec per GPU
Img/sec per GPU: 330.5 +-0.8
Total img/sec on 4 GPU(s): 1321.9 +-3.2

使用普通GPU调度训练Resnet50

  1. 使用以下命令向集群提交作业。
    arena submit mpi \
  --name=pytorch-4-resnet50 \
  --gpus=1 \
  --workers=4 \
  --image=registry.cn-hangzhou.aliyuncs.com/kubernetes-image-hub/pytorch-benchmark:torch1.6.0-py3.7-cuda10.1 \
  "mpirun --allow-run-as-root -np "4" -bind-to none -map-by slot -x NCCL_DEBUG=INFO -x NCCL_SOCKET_IFNAME=eth0 -x LD_LIBRARY_PATH -x PATH --mca pml ob1 --mca btl_tcp_if_include eth0 --mca oob_tcp_if_include eth0 --mca orte_keep_fqdn_hostnames t --mca btl ^openib python /examples/pytorch_synthetic_benchmark.py --model=resnet50 --batch-size=64"
  2. 执行以下命令，查看当前作业运行情况。
    arena get pytorch-4-resnet50 --type mpijob

    预期输出：

    Name:      pytorch-4-resnet50
Status:    RUNNING
Namespace: default
Priority:  N/A
Trainer:   MPIJOB
Duration:  10s

Instances:
  NAME                               STATUS   AGE  IS_CHIEF  GPU(Requested)  NODE
  ----                               ------   ---  --------  --------------  ----
  pytorch-4-resnet50-launcher-qw5k6  Running  10s  true      0               cn-shanghai.192.168.16.173
  pytorch-4-resnet50-worker-0        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-resnet50-worker-1        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-resnet50-worker-2        Running  10s  false     1               cn-shanghai.192.168.16.173
  pytorch-4-resnet50-worker-3        Running  10s  false     1               cn-shanghai.192.168.16.173
  3. 执行以下命令，查看当前日志信息。
    arena logs -f pytorch-4-resnet50

    预期输出：

    Model: resnet50
Batch size: 64
Number of GPUs: 4
Running warmup...
Running benchmark...
Iter #0: 313.1 img/sec per GPU
Iter #1: 312.8 img/sec per GPU
Iter #2: 313.0 img/sec per GPU
Iter #3: 312.2 img/sec per GPU
Iter #4: 313.7 img/sec per GPU
Iter #5: 313.2 img/sec per GPU
Iter #6: 313.6 img/sec per GPU
Iter #7: 313.0 img/sec per GPU
Iter #8: 311.3 img/sec per GPU
Iter #9: 313.6 img/sec per GPU
Img/sec per GPU: 313.0 +-1.3
Total img/sec on 4 GPU(s): 1251.8 +-5.3

性能对比

基于如上4个测试用例性能对比结果如下：gpu32
基于上图性能对比，可知经过GPU拓扑感知调度后，Pytorch分布式训练的效果有了很大的提升。
说明 GPU拓扑感知调度提升结果与您使用的模型以及集群的环境有一定关系，您可以参考上述使用示例，评测自己的模型。