perf-profile

Profiling C code with Linux perf made easy

What's this?

perf annotate is not for a human

Suppose you profiled C code using Linux perf and found a slow function, vm_call_iseq_setup.

You may run:

$ perf annotate vm_call_iseq_setup

or push "a" on perf report, and get:

Because it relies on objdump -S, you need to read C code mixed with machine code, which is too hard for a human.

You could use OProfile's opannotate -s which implements that feature. But unlike perf annotate, opannotate -s did't work for my use case: C code dynamically compiled by Ruby's JIT. So I needed to stick with perf.

It's perf annotate, but human-readable

Using this tool, you can run:

$ perf script report profile -S vm_call_iseq_setup

and see C code with profile information, without mixing machine code:

Prerequisite

perf with libpython support is required.

If you use Ubuntu, you'd need to manually build it as it's not supported by default:

$ git clone --branch=v4.15 https://github.com/torvalds/linux
$ cd linux/tools/perf
# optional: libelf-dev libunwind-dev libaudit-dev libslang2-dev libdw-dev
$ sudo apt install libpython-dev python-pip
$ make

Of course, your binary to be profiled needs to be compiled with debug symbols, and the source must be kept.

Installation

Put this repository as $prefix/libexec/perf-core where $prefix is $HOME by default for perf built manually.

$ git clone https://github.com/k0kubun/perf-profile ~/libexec/perf-core

Usage

Run perf record --call-graph=dwarf normally, and run:

# Annotate sources from all traces
$ perf script report profile

# Annotate traces above a specified symbol
$ perf script report profile -S funcname

You can also trigger this by pushing r on perf report.

Project status

Experimental. The interpretation of objdump --dwarf might be wrong.

License

GNU GPL License version 2