Diffbench

Diffbench is a tool I made during many performance patches to:

Rails
- ActiveRecord - #5467
- ActiveModel - #5431
- ActiveSupport - #4493
- ActionPack - #5957
Mail - #396, #366

It runs a same benchmark code before and after applying a patch.

Requirements

Installation

gem install diffbench

Usage

Create the following benchmark file in the git root of the project:

require 'diffbench'

$LOAD_PATH << "./lib"
require "mail"

DiffBench.bm do
  report("headers parsing when long") do
    Mail::Header.new("X-Subscriber: 1111\n"* 1000)
  end
  report("headers parsing when tiny") do
    10.times do
      Mail::Header.new("X-Subscriber: 1111\n"* 10)
    end
  end
  report("headers parsing when empty") do
    100.times do
      Mail::Header.new("")
    end
  end
end

Run:

diffbench <file>

If the working tree is dirty than diffbench will run benchmark against dirty and clean tree. If the working tree is not dirty than diffbench will run benchmark against current HEAD and commit previous to HEAD.

Output:

Running benchmark with current working tree
Checkout HEAD^
Running benchmark with HEAD^
Checkout to previous HEAD again

                    user     system      total        real
----------------------------------headers parsing when long
After patch:    0.100000   0.000000   0.100000 (  0.089926)
Before patch:   0.700000   0.000000   0.700000 (  0.697444)

----------------------------------headers parsing when tiny
After patch:    0.000000   0.000000   0.000000 (  0.009930)
Before patch:   0.020000   0.000000   0.020000 (  0.024283)

---------------------------------headers parsing when empty
After patch:    0.010000   0.000000   0.010000 (  0.002160)
Before patch:   0.000000   0.000000   0.000000 (  0.002354)

Is DiffBench safe for my repo?

DiffBench is using git stash and git checkout "HEAD^" commands to modify code in a repo. This means that you are able to recover your code even after ruby segfaults.

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diffbench