using ebpf for linux performance analyses

© 2019 Percona. 1

Peter Zaitsev, CEO Percona

Using eBPF for Linux Performance AnalysesIn 25 Minutes…

February 3rd, 2019

FOSDEM, Monitoring and ObservabilityBrussels, Belgium

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Question

Who is familiar with eBPF ?

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About Myself

Performance Geek turned CEO, who kept

his passion

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About the Presentation

eBPF Overview

Practical examples of eBPF based tools

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eBPF History and Linux Support

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eBPF - Extended Berkeley Packet Filter

Berkeley Packet Filter - Originated in 1992 as efficient virtual machine for Packet Filtering

Extended Berkeley Packet Filter – Extended Version found in Linux

General Event Processing Framework

JIT Compiler for high efficiency

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eBPF in Linux

Has been in Linux Kernel since 2014

Actively being improved

Integrated in “perf” tooling

system

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Improvements in recent Kernels

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eBPF Programs

Linux Kernel can load programs in custom byte code

Programs verified before load to prevent misuse

LLVM Clang can compile to eBPF byte code

This compilation is kernel-dependent

Few will need to write eBPF programs Directly

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eBPF Code Example

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eBPF User Space vs Kernel

Source: http://www.brendangregg.com/ebpf.html

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eBPF in Linux Summary

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eBPF features in different kernel versions

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Tracing Landscape per Brendan Gregg

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Things to note

•perf-tools-unstable

•Iovisor/bcc

•Iovisor/ply

•…

Not all the tools

available in the single package

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Iovisor bcc installation

Detailed Instructions: https://github.com/iovisor/bcc/blob/master/INSTALL.md

Note: Tools installed to /usr/share/bcc/tools not added to PATH automatically

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Tools in Action

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Profile: Better “poor man’s profiler”

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Biolatency: Block Device Latency

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Biosnoop: Block Device IO Tracing

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Ext4dist: Filesystem Latency per Operation

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Ext4slower: Trace Slow (or all) IO

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Cachestat: File System Cache Performance

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Runqlat: CPU RunQueue Latency

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Execsnoop: Trace Program Starts

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Opensnoop: Trace Opened Files

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Tcpconnect: Trace TCP Connections

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Tcpretrans: TCP Retransmits Details

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Gethostlatency: DNS Lookup Latency

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All tools available with BCC:

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Ply: Simple Scripting for eBPF

Is not available as packages yet!

git clone https://github.com/iovisor/plycd ply./autogen.sh./configuremake

More Details: https://wkz.github.io/ply/

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Ply Example

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Ply Language#!/usr/bin/env ply

kprobe:SyS_execve {

@exec[tid()] = mem(arg(0), "128s");

i = 0;

unroll(16) {

argi = mem(arg(1) + i * sizeof("p"), "p");

if (!argi)

return;

@argv[tid(), i] = mem(argi, "128s");

i = i + 1;

}

}

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Lets Get Some History !

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eBPF and Trending

Command Line Frontends are great for interactive troubleshooting of current problems

Not very helpful if you want to analyze the past

How do we get the data into Monitoring System ?

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Meet Cloudflare’s eBPF Exporter

Get results of your eBPF Probes to Prometheus

Can plot Prometheus data using Grafana and other Tools

Use for Alerting with Prometheus Alert Manager

More Info: https://blog.cloudflare.com/introducing-ebpf_exporter/

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In Search of the Response Time Histograms

Autodesk Research: https://www.autodeskresearch.com/publications/samestats

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eBPF Exporter Architecture

Uses BCC Frontend (Library)

Can be used to take BCC Programs output and expose them in Prometheus Format

Mind Performance Overhead of eBPF Probes

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eBPF Overhead

eBPF Programs can be run million+ times per second per core

More Details: https://github.com/cloudflare/ebpf_exporter/tree/master/benchmark

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Installing eBPF Exporter

• Install Exporter (Binaries Available)

• https://github.com/cloudflare/ebpf_exporter/releases

• Provide Instrumentation Configuration

• https://github.com/cloudflare/ebpf_exporter/tree/master/examples

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Percona Monitoring and Management (PMM)

100% Free and Open Source

Purpose Built for Open Source Databases

Based on Grafana and Prometheus

Easy to Install and Use

Where should we visualize it ?

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Adding eBPF Exporter to PMM

pmm-admin add external:service ebpf --service-port=9435

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Device IO Response Histogram

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PMM System Overview Dashboard

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Adding Latency Histograms

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Can see outliers

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eBPF Future

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Bpftrace – Dtrace Replacement

See More: http://www.brendangregg.com/blog/2018-10-08/dtrace-for-linux-2018.html

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Further Reading List

https://github.com/zoidbergwill/awesome-ebpf

https://slideplayer.com/slide/12710510/

http://www.brendangregg.com/ebpf.html

http://vger.kernel.org/netconf2018_files/BrendanGregg_netconf2018.pdf

http://www.brendangregg.com/Slides/Velocity2017_BPF_superpowers.pdf

https://lwn.net/Articles/740157/

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Thank You!