linux-perf-tools

Perf is a performance analyzing tool in Linux.

Perf (Linux profiling with performance counter) is powerful: it can instrument CPU performance counters, tracepoints, kprobes, and uprobes (dynamic tracing). It is capable of lightweight profiling. It is also included in the Linux kernel, under tools/perf, and is frequently updated and enhanced.

perf began as a tool for using the performance counters subsystem in Linux, and has had various enhancements to add tracing capabilities.

Section1: C++ application using perf

You may need to install linux-tools-common and other packages for the specific kernel:

sudo apt install linux-tools-common

linux-tools-4.15.0-88-generic
linux-cloud-tools-4.15.0-88-generic

Optionally

You may also want to install one of the following packages to keep up to date:

linux-tools-generic
Linux-cloud-tools-generic

Perf analysis on C++ Fibonacci Number (Naive Algorithm)

The first approach to test Fibonacci number is using recursion and this will be indeed slow for greater value of n.

Computing for n > 40 takes considerable time.

Fig. 1 Pusedo code for Fibonacci number using recursion

In a new terminal type:

cd test-code-flame-graph
mkdir build
cd build
cmake ..
make

Binaries will be placed in build folder and this test had been done with following CMake settings:

cmake_minimum_required(VERSION 3.5.1)
project(test-code-flame-graph)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11") 

Creating a Perf.data for C++ Fibonacci Number

In a new terminal type:

sudo perf record --call-graph dwarf ./test-code-flame-graph

Generating flameGraph from perf.data

In new separate terminal type:

sudo perf script | ./stackcollapse-perf.pl | ./famegraph.pl > perf.svg

Generated flameGraph

Fig. 2 Generated flameGraph for Fibonacci number using recursion

Section2: C++ shared library profiling using perf

Similarly, we can only profile C++ shared libraray using same way.

perf report -d library.so

Generated flameGraph for shared library of C++ Fibonacci

Fig. 3 Generated flameGraph for C++ Fibonacci number shared library using recursion

Section3: Python script with perf

In new separate terminal type:

git clone [email protected]:brendangregg/FlameGraph.git

cd FlaneGraph
python -m flamegraph -o perf.log myscript.py

This will generate a perf.log file in root folder of FlameGraph.

where myscript.py is supposed to be your python scripts which you wants to have analyze.

Now to run Brendan Gregg’s FlameGraph tool against the output:

flamegraph.pl --title "MyScript CPU" perf.log > perf.svg

Where flamegraph.pl is located in root folder of FlameGraph, the generated file perf.svg will be saved in same root folder i.e. FlameGraph.

Fig. 4. CPU FlameGraph for myscript.py. Fig. 2. CPU FlameGraph for myscript.py