Kernel Recipes 2016 - Control Group Status Update
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Cgroup v2 provides a consistent hierarchical system for controlling and accounting system resources. It establishes common resource domains and delegation across controllers like memory, I/O, and CPUs. While memory, I/O, and process controllers are supported in the kernel, CPU controller support remains outside the kernel due to design disagreements. Userland tools like systemd will provide full support once the CPU controller is merged.
Kernel Recipes 2016 - Control Group Status Update
- 1. cgroup v2 status update Tejun Heo, facebook kernel recipes 2016
- 2. timeline ● Preliminary work started with gradual cleanups in Sep, 2012. ● Experimental v2 unified hierarchy support implemented in Apr, 2014. ● cgroup v2 interface exposed in Nov, 2016 (Linux v4.5). ● memory, io and pids controller are supported currently. ● Unfortunately, cpu controller support is still out of tree.
- 3. what’s v2 about? Comprehensive and consistent hierarchical accounting and control of all significant resource consumptions in the system.
- 4. what does v2 do? ● Establish common resource domain across different resource types so that they can cooperate. ○ page cache writeback ○ resources spent for operations which can’t be charged immediately ● Differing levels of granularity. ● Well-defined and consistent design in the core and across all controllers. ○ delegation ○ common resource models and interface conventions ● Other cleanups. ○ notification
- 5. cpu controller controversy ● cpu controller support is still out of tree. ● Disagreements around v2 core design features. ○ no-internal-processes constraint ○ process granularity, rgroup ● Discussion is still on-going. ○ http://lwn.net/Articles/697366/ ○ http://lkml.kernel.org/r/20160805170752.GK2542@mtj.duckdns.org
- 6. other things ● pids controller added on v4.3. ● Namespace support added on v4.6. Still shaking out some bugs. ● rdma controller being worked on.
- 7. userland support ● systemd 232 will have full cgroup v2 support including cpu controller. ● It can also use cgroup v2 for process management while using v1 for resource control. ● Working on libvirt support. ● We are deploying cgroup v2 in combination with mainline systemd.