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User Guide for Linux Instances

AWS Documentation » Amazon EC2 » User Guide for Linux Instances » Amazon EC2 Instances » Configuring Your Amazon Linux Instance » Optimizing CPU Options

Optimizing CPU Options

Amazon EC2 instances support Intel Hyper-Threading Technology (HT Technology), which enables multiple threads to run concurrently on a single Intel Xeon CPU core. Each thread is represented as a virtual CPU (vCPU) on the instance. An instance has a default number of CPU cores, which varies according to instance type. For example, an m5.xlarge instance type has two CPU cores and two threads per core by default—four vCPUs in total.

In most cases, there is an Amazon EC2 instance type that has a combination of memory and number of vCPUs to suit your workloads. However, you can specify the following CPU options to optimize your instance for specific workloads or business needs:

You can specify these CPU options during instance launch. There is no additional or reduced charge for specifying CPU options. You're charged the same as instances that are launched with default CPU options.

Rules for Specifying CPU Options

To specify the CPU options for your instance, be aware of the following rules:

CPU Cores and Threads Per CPU Core Per Instance Type

The following tables list the instance types that support specifying CPU options. For each type, the table shows the default and supported number of CPU cores and threads per core.

Specifying CPU Options for Your Instance

You can specify CPU options during instance launch. The following examples are for an r4.4xlarge instance type, which has the following default values:

Disabling Intel HT Technology

To disable Intel HT Technology, specify one thread per core.

To disable Intel HT Technology during instance launch (Console)

1. Follow the Launching an Instance Using the Launch Instance Wizard procedure.

2. On the Configure Instance Details page, for CPU options, choose Specify CPU options.

3. For Core count, choose the number of required CPU cores. In this example, to specify the default CPU core count for an r4.4xlarge instance, choose 8.

4. To disable Intel HT Technology, for Threads per core, choose 1.

5. Continue as prompted by the wizard. When you've finished reviewing your options on the Review Instance Launch page, choose Launch. For more information, see Launching an Instance Using the Launch Instance Wizard.

To disable Intel HT Technology during instance launch (AWS CLI)

• Use the run-instances AWS CLI command and specify a value of 1 for ThreadsPerCore for the --cpu-options parameter. For CoreCount, specify the number of CPU cores. In this example, to specify the default CPU core count for an r4.4xlarge instance, specify a value of 8.

  aws ec2 run-instances --image-id ami-1a2b3c4d --instance-type r4.4xlarge --cpu-options "CoreCount=8,ThreadsPerCore=1" --key-name MyKeyPair

Specifying a Custom Number of vCPUs

You can customize the number of CPU cores and threads per core for the instance.

To specify a custom number of vCPUs during instance launch (console)

The following example launches an r4.4xlarge instance with six vCPUs.

1. Follow the Launching an Instance Using the Launch Instance Wizard procedure.

2. On the Configure Instance Details page, for CPU options, choose Specify CPU options.

3. To get six vCPUs, specify three CPU cores and two threads per core, as follows:

   • For Core count, choose 3.

   • For Threads per core, choose 2.

4. Continue as prompted by the wizard. When you've finished reviewing your options on the Review Instance Launch page, choose Launch. For more information, see Launching an Instance Using the Launch Instance Wizard.

To specify a custom number of vCPUs during instance launch (AWS CLI)

The following example launches an r4.4xlarge instance with six vCPUs.

1. Use the run-instances AWS CLI command and specify the number of CPU cores and number of threads in the --cpu-options parameter. You can specify three CPU cores and two threads per core to get six vCPUs.

   aws ec2 run-instances --image-id ami-1a2b3c4d --instance-type r4.4xlarge --cpu-options "CoreCount=3,ThreadsPerCore=2" --key-name MyKeyPair

2. Alternatively, specify six CPU cores and one thread per core (disable hyperthreading) to get six vCPUs:

   aws ec2 run-instances --image-id ami-1a2b3c4d --instance-type r4.4xlarge --cpu-options "CoreCount=6,ThreadsPerCore=1" --key-name MyKeyPair

Viewing the CPU Options for Your Instance

You can view the CPU options for an existing instance in the Amazon EC2 console or by describing the instance using the AWS CLI.

To view the CPU options for an instance (Console)

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

2. In the left navigation pane, choose Instances, and select the instance.

3. Choose Description and view the Number of vCPUs field.

4. To view the core count and threads per core, choose the Number of vCPUs field value.

To view the CPU options for an instance (AWS CLI)

• Use the describe-instances AWS CLI command.

  aws ec2 describe-instances --instance-ids i-123456789abcde123

  ...
  
              "Instances": [
                  {
                      "Monitoring": {
                          "State": "disabled"
                      }, 
                      "PublicDnsName": "ec2-198-51-100-5.eu-central-1.compute.amazonaws.com", 
                      "State": {
                          "Code": 16, 
                          "Name": "running"
                      }, 
                      "EbsOptimized": false, 
                      "LaunchTime": "2018-05-08T13:40:33.000Z", 
                      "PublicIpAddress": "198.51.100.5", 
                      "PrivateIpAddress": "172.31.2.206", 
                      "ProductCodes": [], 
                      "VpcId": "vpc-1a2b3c4d", 
                      "CpuOptions": {
                          "CoreCount": 34, 
                          "ThreadsPerCore": 1
                      }, 
                      "StateTransitionReason": "", 
  
  ...

  In the output that's returned, the CoreCount field indicates the number of cores for the instance. The ThreadsPerCore field indicates the number of threads per core.

Alternatively, connect to your instance and use a tool such as lscpu to view the CPU information for your instance.

You can use AWS Config to record, assess, audit, and evaluate configuration changes for instances, including terminated instances. For more information, see Getting Started with AWS Config in the AWS Config Developer Guide.

On this page:

• Rules for Specifying CPU Options
• CPU Cores and Threads Per CPU Core Per Instance Type
• Specifying CPU Options for Your Instance
• Viewing the CPU Options for Your Instance