Among the pull requests arriving late in the merge window for the Linux 6.1 cycle are “sched/psi” updates for code improvements around pressure blocking information.
Linux Pressure Stall Information (PSI) is used to quantify CPU, memory, and I/O contention under load when the system is running low on resources. Linux’s PSI helps analyze resource issues with this real-time aggregated information and comes into play especially around memory deletions.
With Linux 6.1 it is now possible to enable or disable pressure stall information at the level of each cgroup. This per cgroup control around PSI information is useful because this accounting can add additional overhead to workloads and therefore can be selectively disabled if needed. This interface is exposed via cgroup.pressure via sysfs to enable/disable cgroup PSI accounting.
The other notable change with the PSI updates for Linux 6.1 is some performance optimizations. The developers found a 4-9% speedup under a scheduler micro-benchmark with the latest PSI code changes.
The list of sched/psi fixes for the Linux 6.1 merge window can be found via this now honored pull request.