Linux 6.1 Picks Up Some Improvements For Pressure Stall Information (PSI)

Among the pull requests coming in late in the merge window for the Linux 6.1 cycle is the "sched/psi" updates for the code improvements around Pressure Stall Information.

Linux's Pressure Stall Information (PSI) is used for quantifying CPU, memory, and I/O contention under load when the system is starved for resources. Linux's PSI helps to analyze resource issues with this aggregated real-time information and particularly comes into play around out-of-memory kills.

With Linux 6.1 there is now support for turning the Pressure Stall Information on or off at a per-cgroup level. This per-cgroup control around PSI information is useful since this accounting can add some extra overhead to workloads and thus can be selectively disabled where desired. This interface is exposed via cgroup.pressure via sysfs for enabling/disabling cgroup PSI accounting.

The other notable change with the PSI updates for Linux 6.1 are some performance optimizations. Developers have found a 4~9% speed-up under a scheduler micro-benchmark with the latest PSI code changes.

The list of sched/psi patches for the Linux 6.1 merge window can be found via this now honored pull request.