This page describes Pressure Stall Information (PSI), how to use it, tools and components that work with PSI, and some case studies showing how PSI is used in production today for resource control in large data centers.
Overview
PSI provides for the first time a canonical way to see resource pressure increases as they develop, with new pressure metrics for three major resources—memory, CPU, and IO.
These pressure metrics, in conjunction with cgroup2 and other kernel and userspace tools described below, allow you to detect resource shortages while they’re developing, and respond intelligently—by pausing or killing non-essentials, reallocating memory in the system, load shedding, or other actions.
PSI stats are like barometers that provide fair warning of impending resource shortages, enabling you to take more proactive, granular, and nuanced steps when resources start becoming scarce.
See the PSI git repo for additional information.
We know that using swap space instead of RAM (memory) can severely slow down the performance of Linux. So then, one might ask, since I have more than enough memory available, wouldn’t it better to remove swap space completely? The short answer is, No. There are performance benefits when swap is enabled, even when you have more than enough ram.
About a week ago many users may have noticed instability on our hosted ZeroTier Central. Network controllers would flicker on and off, and eventually the whole service needed to be restarted across our cluster. 500 errors and timeouts were a thing.