psimon

monitoring utility for pressure stall information

What is Pressure Stall Information?

The psi feature identifies and quantifies the disruptions caused by resource contention and the time impact it has on complex workloads or even entire systems.

Can't We Already Get Interactive System Load Information?

PSI reports the percentage of wallclock time in which tasks are waiting for a CPU to run on. This is more granular and indicitave of system health than system load [3].

Runtime Requirements

Kernel must support psi (must be built with CONFIG_PSI=y), which requires at least linux 4.20 If your kernel is compiled with CONFIG_PSI_DEFAULT_DISABLED, you will need to pass a command line flag to pass psi=1 to the kernel on boot.

Build Requirements

git gcc make

Build Instructions

git clone --recurse-submodules https://github.com/holmanb/psimon.git
cd psimon
make
make psimon

Usage

currently psimon doesn't require any arguments and shows PSI counter values in realtime

Future Work

• add cgroup support
• parse "full" pressure counters for io && memory
• add flags for selecting memory, io, or cpu
• randomized file names in /tmp
• various TODO cleanup items in codebase
• add units
• add averages
• fix y axis color issue (see )

Pressure Stall Information References

[1] Kernel Docs at kernel.org

[2] Kernel Source Docs

[3] Description At lwn.net

[4] Facebook Helped Develop PSI and includes their use cases