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.

A tool to monitor I/O latency in real time. It shows disk latency in the same way as ping shows network latency.

Homepage: https://github.com/koct9i/ioping/ (migrated from http://code.google.com/p/ioping/)

Please send your patches, issues and questions to https://github.com/koct9i/ioping/issues/

blkreplay is a GPL’ed userspace toolkit, driving the block layer of Linux (or other Unix-like OSes) while measuring latency and throughput of IO operations for later visualization (so-called “sonar diagrams” and others).

In addition to artificial loads like random read-write sweeps and various kinds of overload tests, blkreplay can replay natural loads which have been recorded by blktrace (or Windows DiskMon) at heavily-loaded production servers at big data centers.

BCC is a toolkit for creating efficient kernel tracing and manipulation programs, and includes several useful tools and examples. It makes use of extended BPF (Berkeley Packet Filters), formally known as eBPF, a new feature that was first added to Linux 3.15. Much of what BCC uses requires Linux 4.1 and above.

eBPF was described by Ingo Molnár as:

One of the more interesting features in this cycle is the ability to attach eBPF programs (user-defined, sandboxed bytecode executed by the kernel) to kprobes. This allows user-defined instrumentation on a live kernel image that can never crash, hang or interfere with the kernel negatively.

BCC makes BPF programs easier to write, with kernel instrumentation in C (and includes a C wrapper around LLVM), and front-ends in Python and lua. It is suited for many tasks, including performance analysis and network traffic control.

EnhanceIO can work with any block device, be it an entire physical disk, an individual disk partition, a RAIDed DAS device, a SAN volume, a device mapper volume or a software RAID (md) device.

Feihong Hsu http://pyvideo.org/video/2194/asynchronous-io-in-python-3 http://www.chipy.org/ I'm going to talk about PEP 3156 and go over basic usage of the r...

Back in October 2012 Python's Benevolent Dictator for Life, Guido van Rossum, embarked on a mission to add asynchronous I/O to the Python standard library, t...