cpu

The number of `cpu` units reserved for the container. This parameter maps to `CpuShares` in the docker container create commandand the `--cpu-shares` option to docker run. This field is optional for tasks using the Fargate launch type, and the only requirement is that the total amount of CPU reserved for all containers within a task be lower than the task-level `cpu` value. You can determine the number of CPU units that are available per EC2 instance type by multiplying the vCPUs listed for that instance type on the Amazon EC2 Instances detail page by 1,024. Linux containers share unallocated CPU units with other containers on the container instance with the same ratio as their allocated amount. For example, if you run a single-container task on a single-core instance type with 512 CPU units specified for that container, and that's the only task running on the container instance, that container could use the full 1,024 CPU unit share at any given time. However, if you launched another copy of the same task on that container instance, each task is guaranteed a minimum of 512 CPU units when needed. Moreover, each container could float to higher CPU usage if the other container was not using it. If both tasks were 100% active all of the time, they would be limited to 512 CPU units. On Linux container instances, the Docker daemon on the container instance uses the CPU value to calculate the relative CPU share ratios for running containers. The minimum valid CPU share value that the Linux kernel allows is 2, and the maximum valid CPU share value that the Linux kernel allows is 262144. However, the CPU parameter isn't required, and you can use CPU values below 2 or above 262144 in your container definitions. For CPU values below 2 (including null) or above 262144, the behavior varies based on your Amazon ECS container agent version:

• Agent versions less than or equal to 1.1.0: Null and zero CPU values are passed to Docker as 0, which Docker then converts to 1,024 CPU shares. CPU values of 1 are passed to Docker as 1, which the Linux kernel converts to two CPU shares.

• Agent versions greater than or equal to 1.2.0: Null, zero, and CPU values of 1 are passed to Docker as 2.

• Agent versions greater than or equal to 1.84.0: CPU values greater than 256 vCPU are passed to Docker as 256, which is equivalent to 262144 CPU shares. On Windows container instances, the CPU limit is enforced as an absolute limit, or a quota. Windows containers only have access to the specified amount of CPU that's described in the task definition. A null or zero CPU value is passed to Docker as `0`, which Windows interprets as 1% of one CPU.