cgroup-v2-io-controller · shipping · also cgroup I/O controller, io.max, io.stat

cgroup v2 I/O controller

The cgroup v2 I/O controller accounts for and regulates block-device I/O for hierarchical groups of Linux processes.

Related Observatory article: cgroup v2 I/O controller on hesela.com

io.stat reports device-keyed byte and operation counts. io.max sets directional bytes-per-second and IOPS limits; temporary bursts are permitted. [1]

Buffered writeback needs filesystem support. Its ownership is per inode, can switch between groups, and can misattribute concurrent cross-group writers. This differs from per-process accounting. [2]

IOCost models request cost rather than equating bytes or operation counts with device occupancy; its memory-reclaim path can issue over-budget I/O on credit to avoid blocking another group. This is a source-described control mechanism, not a host measurement. [3]

Relations

related

Pressure Stall Information (PSI), Process I/O accounting, Budget Fair Queueing (BFQ)

Limitations

• These counters do not certify crash durability. [1]

Citations

1. Linux 6.12: cgroup v2 I/O interface and writeback (accessed 2026-11-03)
2. Linux 6.12: cgroup writeback ownership (accessed 2026-11-03)
3. Heo et al.: IOCost, ASPLOS 2022, sections 3.2-3.5; DOI 10.1145/3503222.3507727 (accessed 2026-11-04)

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