profiling/

Profiling Code

We can use the go tooling in conjunction with the Graph Visualization Tools and Ghostscript. These tools will allow us to graph the profiles we create.

Installing Tools

Graph Visualization Tools
Download the package for your target OS/Arch: http://www.graphviz.org/Download.php

Ghostscript
Download and uncompress the source code: http://ghostscript.com/download/gsdnld.html

./configure
make
sudo make install

go-wrk
go-wrk is a modern HTTP benchmarking tool capable of generating significant load when run on a single multi-core CPU. It builds on go language go routines and scheduler for behind the scenes async IO and concurrency.

go get -u github.com/tsliwowicz/go-wrk

Building and Running the Project

We have a website that we will use to learn and explore more about profiling. This project is a search engine for RSS feeds. Run the website and validate it is working.

go build
./project

http://localhost:5000/search

Adding Load

To add load to the service while running profiling we can run these command.

Use 10 connections for 2 minute on CNN, BBC and NYT about house:
go-wrk -M POST -c 10 -d 120 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

GODEBUG

GODBUG is an environment variable that allows us to get information from the runtime about the scheduler and the garabage collector.

The Basics

Learn the basics of using GODEBUG for tracing.
Memory Tracing | Scheduler Tracing

Memory Trace for Project

Run the website redirecting the stdout (logs) to the null device. This will allow us to just see the trace information from the runtime.

GODEBUG=gctrace=1 ./project > /dev/null

Put some load of the web application for 20 seconds.

go-wrk -M POST -c 10 -d 20 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

Scheduler Trace for Project

Run the website redirecting the stdout (logs) to the null device. This will allow us to just see the trace information from the runtime.

GODEBUG=schedtrace=1000 GOMAXPROCS=2 ./project > /dev/null

Put some load of the web application for 20 seconds.

go-wrk -M POST -c 10 -d 20 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

PPROF

Go provides built in support for retrieving profiling data from your running Go applications.

Raw http/pprof

Add the following import so we can include the profiling route to our web service.

import _ "net/http/pprof"

Build the project again and start it.

go build
./project

Look at the basic profiling stats from the new endpoint.

http://localhost:5000/debug/pprof

Run a single search from the Browser and then refresh the profile information.

http://localhost:5000/search?term=house&cnn=on

Put some load of the web application for 10 seconds. Review the raw profiling information once again.

go-wrk -M POST -c 10 -d 10 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

Interactive Profiling

Using the Go pprof tool we can interact with the profiling data.

Put some load of the web application for 2 minutes using a single connection.

go-wrk -M POST -c 1 -d 120 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

Run the Go pprof tool in another window or tab to review heap information.

go tool pprof ./project http://localhost:5000/debug/pprof/heap

Run the Go pprof tool in another window or tab to review cpu information.

go tool pprof ./project http://localhost:5000/debug/pprof/profile

Explore using the top and list commands.

Generate PDF Call Graph

Generate call graphs for both the cpu and memory profiles.

// Create output files.
curl -s http://localhost:5000/debug/pprof/profile > cpu.out
go tool pprof ./project cpu.out
(pprof) web

curl -s http://localhost:5000/debug/pprof/heap > mem.out
go tool pprof ./project mem.out
(pprof) web

// Call into the endpoints directly and generate graphs.
go tool pprof -web ./project http://localhost:5000/debug/pprof/heap
go tool pprof -web ./project http://localhost:5000/debug/pprof/profile

Go Torch

Tool for stochastically profiling Go programs. Collects stack traces and synthesizes them into a flame graph.

https://github.com/uber/go-torch

Put some load of the web application for 2 minutes.

go-wrk -M POST -c 10 -d 120 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

Run the torch tool and visualize the profile.

go-torch -u http://localhost:5000/

Comparing Profiles

Take a snapshot of the current heap profile. Then do the same for the cpu profile.

curl -s http://localhost:5000/debug/pprof/heap > base.heap

After some time, take another snapshot:

curl -s http://localhost:5000/debug/pprof/heap > current.heap

Now compare both snapshots against the binary and get into the pprof tool:

go tool pprof -alloc_space -base base.heap memory_trace current.heap

-inuse_space  : Display in-use memory size
-inuse_objects: Display in-use object counts
-alloc_space  : Display allocated memory size
-alloc_objects: Display allocated object counts

Tracing

Run the web application with tracing on. Show the code that produces the trace.

./project trace

Put some load of the web application for 2 minutes.

go-wrk -M POST -c 10 -d 120 -no-ka "http://localhost:5000/search?term=house&cnn=on&bbc=on&nyt=on"

Kill the web application to produce the trace.out file.

Run the Go trace tool.

go tool trace trace.out

Links

http://golang.org/blog/profiling-go-programs
http://golang.org/pkg/runtime/pprof/
https://golang.org/pkg/net/http/pprof/
https://godoc.org/rsc.io/pprof_mac_fix

Code Review

HTTP Service (Go Playground)

All material is licensed under the Apache License Version 2.0, January 2004.