0e9b92090c
In order to implement the `full-pcpus-only` cpumanager policy option, we leverage the implementation of the algorithm which picks CPUs. By design, CPUs are taken from the biggest chunk available (socket or NUMA zone) to physical cores, down to single cores. Leveraging this, if the requested CPU count is a multiple of the SMT level (commonly 2), we're guaranteed that only full physical cores will be taken. The hidden assumption here is this holds true by construction iff the user reserved CPUs (if any) considering full physical CPUs. IOW, if the user did intentionally or mistakely reserve single threads which are no core siblings[1], then the simple check we implemented is not sufficient. A easy example can probably outline this better. With this setup: cores: [(0, 4), (1, 5), (2, 6), (3, 8)] (in parens: thread siblings). SMT level: 2 (each tuple is 2 elements) Reserved CPUs: 0,1 (explicit pick using `--reserved-cpus`) A container then requests 6 cpus. full-pcpus-only check: 6 % 2 == 0. Passed. The CPU allocator will take first full cores, (2,6) and (3,8), and will then pick the remaining single CPUs. The allocation will succeed, but it's incorrect. We can fix this case with a stricter precheck. We need to additionally consider all the core siblings of the reserved CPUs as unavailable when computing the free cpus, before to start the actual allocation. Doing so, we fall back in the intended behavior, and by construction all possible CPUs allocation whose number is multiple of the SMT level are now correct again. +++ [1] or thread siblings in the linux parlance, in any case: hyperthread siblings of the same physical core Signed-off-by: Francesco Romani <fromani@redhat.com>
Kubernetes (K8s)
Kubernetes, also known as K8s, is an open source system for managing containerized applications across multiple hosts. It provides basic mechanisms for deployment, maintenance, and scaling of applications.
Kubernetes builds upon a decade and a half of experience at Google running production workloads at scale using a system called Borg, combined with best-of-breed ideas and practices from the community.
Kubernetes is hosted by the Cloud Native Computing Foundation (CNCF). If your company wants to help shape the evolution of technologies that are container-packaged, dynamically scheduled, and microservices-oriented, consider joining the CNCF. For details about who's involved and how Kubernetes plays a role, read the CNCF announcement.
To start using K8s
See our documentation on kubernetes.io.
Try our interactive tutorial.
Take a free course on Scalable Microservices with Kubernetes.
To use Kubernetes code as a library in other applications, see the list of published components.
Use of the k8s.io/kubernetes module or k8s.io/kubernetes/... packages as libraries is not supported.
To start developing K8s
The community repository hosts all information about building Kubernetes from source, how to contribute code and documentation, who to contact about what, etc.
If you want to build Kubernetes right away there are two options:
You have a working Go environment.
mkdir -p $GOPATH/src/k8s.io
cd $GOPATH/src/k8s.io
git clone https://github.com/kubernetes/kubernetes
cd kubernetes
make
You have a working Docker environment.
git clone https://github.com/kubernetes/kubernetes
cd kubernetes
make quick-release
For the full story, head over to the developer's documentation.
Support
If you need support, start with the troubleshooting guide, and work your way through the process that we've outlined.
That said, if you have questions, reach out to us one way or another.
Community Meetings
The Calendar has the list of all the meetings in Kubernetes community in a single location.
Adopters
The User Case Studies website has real-world use cases of organizations across industries that are deploying/migrating to Kubernetes.
Governance
Kubernetes project is governed by a framework of principles, values, policies and processes to help our community and constituents towards our shared goals.
The Kubernetes Community is the launching point for learning about how we organize ourselves.
The Kubernetes Steering community repo is used by the Kubernetes Steering Committee, which oversees governance of the Kubernetes project.
Roadmap
The Kubernetes Enhancements repo provides information about Kubernetes releases, as well as feature tracking and backlogs.