MemoryProfiler

A memory profiler for Ruby

Requirements

Ruby(MRI) Version 2.1.0 and above.

Installation

Add this line to your application's Gemfile:

gem 'memory_profiler'

And then execute:

$ bundle

Or install it yourself as:

$ gem install memory_profiler

Usage

require 'memory_profiler'
report = MemoryProfiler.report do
  # run your code here
end

report.pretty_print

Or, you can use the .start/.stop API as well:

require 'memory_profiler'

MemoryProfiler.start

# run your code

report = MemoryProfiler.stop
report.pretty_print

NOTE: .start/.stop can only be run once per report, and .stop will be the only time you can retrieve the report using this API.

Options

The report method can take a few options:

• top: maximum number of entries to display in a report (default is 50)
• allow_files: include only certain files from tracing - can be given as a String, Regexp, or array of Strings
• ignore_files: exclude certain files from tracing - can be given as a String or Regexp
• trace: an array of classes for which you explicitly want to trace object allocations

Check out Reporter#new for more details.

pry> require 'memory_profiler'
pry> MemoryProfiler.report(allow_files: 'rubygems'){ require 'mime-types' }.pretty_print
Total allocated 82375
Total retained 22618

allocated memory by gem
-----------------------------------
rubygems x 305879

allocated memory by file
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb x 285433
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb x 18597
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems.rb x 2218
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/specification.rb x 1169
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/defaults.rb x 520
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_gem.rb x 80
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/version.rb x 80

. . .

Also you can print report to file. For this use pretty_print method with to_file option and path_to_your_log_file string:

$ pry
pry> require 'memory_profiler'
pry> MemoryProfiler.report(allow_files: 'rubygems'){ require 'mime-types' }.pretty_print(to_file: 'path_to_your_log_file')

$ less my_report.txt
Total allocated 82375
Total retained 22618

allocated memory by gem
-----------------------------------
rubygems x 305879

. . .

Example Session

You can easily use memory_profiler to profile require impact of a gem, for example:

pry> require 'memory_profiler'
pry> MemoryProfiler.report{ require 'mime-types'  }.pretty_print
Total allocated 82375
Total retained 22618

allocated memory by gem
-----------------------------------
mime-types-2.0 x 3668277
2.1.0-github/lib x 2035704
rubygems x 305879
other x 40

allocated memory by file
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb x 3391763
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb x 2021853
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb x 285433
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb x 227033
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb x 48663
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb x 18597
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so x 8200
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so x 2463
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems.rb x 2218
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/specification.rb x 1169
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/defaults.rb x 520
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader_path.rb x 417
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/version.rb x 409
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types.rb x 361
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/generic_object.rb x 241
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/ext.rb x 200
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json.rb x 120
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_gem.rb x 80
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/version.rb x 80
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime-types.rb x 40
(pry) x 40

allocated memory by location
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 1985709
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:522 x 927503
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 827676
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 499525
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:625 x 281047
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:521 x 265920
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 265920
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:523 x 265920
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 222705
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb:215 x 218105
[REDACTED]

allocated]objects by gem
-----------------------------------
mime-types-2.0 x 56564
2.1.0-github/lib x 22210
rubygems x 3600
other x 1

allocated objects by file
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb x 56237
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb x 21978
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb x 3388
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb x 291
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb x 169
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so x 124
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems.rb x 53
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so x 37
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/specification.rb x 26
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb x 24
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/defaults.rb x 13
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/version.rb x 7
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types.rb x 6
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader_path.rb x 5
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/ext.rb x 5
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json.rb x 3
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/generic_object.rb x 3
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_gem.rb x 2
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/version.rb x 2
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime-types.rb x 1
(pry) x 1

allocated objects by location
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:522 x 21337
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 21095
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 9972
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:523 x 6648
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:521 x 6648
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 6648
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 3307
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 2955
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:625 x 1663
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:60 x 837
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:224 x 312
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb:62 x 287
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so:0 x 124
[REDACTED]

retained memory by gem
-----------------------------------
mime-types-2.0 x 1496813
2.1.0-github/lib x 519954
rubygems x 76195

retained memory by file
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb x 1447316
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb x 516679
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb x 75946
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb x 48583
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so x 2263
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so x 892
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb x 577
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader_path.rb x 297
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb x 169
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/specification.rb x 80
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types.rb x 40
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/generic_object.rb x 40
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/ext.rb x 40
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/version.rb x 40

retained memory by location
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 516181
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 499525
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 414007
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:625 x 280878
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 132960
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:523 x 66480
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:135 x 58151
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:224 x 52728
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb:62 x 48503
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 17795
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so:0 x 2263
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so:0 x 892
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb:239 x 577
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader_path.rb:15 x 257
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb:124 x 169
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:122 x 89
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:46 x 89
[REDUCTED]

retained objects by gem
-----------------------------------
mime-types-2.0 x 15211
2.1.0-github/lib x 7089
rubygems x 318

retained objects by file
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb x 14918
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb x 7045
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb x 315
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb x 289
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so x 32
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/parser.so x 9
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/specification.rb x 2
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader_path.rb x 2
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/loader.rb x 1
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types.rb x 1
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/version.rb x 1
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/generic_object.rb x 1
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/ext.rb x 1
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/basic_specification.rb x 1

retained objects by location
-----------------------------------
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 7035
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 4987
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 3324
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 2955
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:625 x 1662
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:523 x 1662
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:224 x 312
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 300
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/types/cache.rb:62 x 287
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/x86_64-linux/json/ext/generator.so:0 x 32
/home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:135 x 15
[REDUCTED]

Allocated String Report
-----------------------------------
"application" x 12050
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:522 x 4820
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:521 x 2410
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 2410
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 2410
"" x 6669
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:522 x 6648
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 11
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:266 x 4
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:71 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:72 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:69 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:0 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_gem.rb:39 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:70 x 1
"/" x 3342
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:523 x 3324
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 13
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:60 x 4
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:135 x 1
"encoding" x 3336
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 3324
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 10
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:135 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:60 x 1
"registered" x 3328
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 3324
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 4
"content-type" x 3327
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 3324
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 3
"references" x 2944
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 2940
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 4
"IANA" x 2824
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 1412
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 1412
[REDUCTED]

Retained String Report
-----------------------------------
"IANA" x 2824
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 1412
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:302 x 1412
"application" x 2410
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 1205
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 1205
"base64" x 1527
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/json/common.rb:155 x 1525
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:70 x 1
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 1
"audio" x 300
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 150
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 150
"video" x 188
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 94
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 94
"text" x 155
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:629 x 77
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/gems/2.1.0/gems/mime-types-2.0/lib/mime/type.rb:632 x 77
    /home/sam/.rbenv/versions/2.1.0-github/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55 x 1
[REDUCTED]

The data is also available in the MemoryProfiler::Results object returned.

Retained vs Allocated

The report breaks down 2 key concepts.

Retained: long lived memory use and object count retained due to the execution of the code block.

Allocated: All object allocation and memory allocation during code block.

As a general rule "retained" will always be smaller than or equal to allocated.

Memory profiler will tell you aggregate costs of the above, for example requiring the mime-types gem above results in approx 2MB of retained memory in 22K or so objects. The actual RSS cost will always be slightly higher as MRI heaps are not squashed to size and memory fragments. In future we may be able to calculate a rough long term GC cost of retained objects (for major GCs).

Memory profiler also performs some String analysis to help you find strings that would heavily benefit from #freeze. In the example above the string IANA is retained in memory 2824 times, this costs you a minimum of RVALUE_SIZE (40 on x64) * 2824.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request