Replace <top> label by the required file path

[casperisfine]

For context I'm trying to profile rubygems loading, which mean lot's of the time is spent on the initial file evaluations, whihc appear as <top (required)>.

==================================
  Mode: wall(10)
  Samples: 2653 (58.21% miss rate)
  GC: 718 (27.06%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       416  (15.7%)         416  (15.7%)     (marking)
       715  (27.0%)         312  (11.8%)     Gem::Specification.load
       299  (11.3%)         299  (11.3%)     (sweeping)
       279  (10.5%)         279  (10.5%)     Gem.already_loaded?
       564  (21.3%)         106   (4.0%)     Gem.register_default_spec
        95   (3.6%)          80   (3.0%)     Gem::Specification#files
        72   (2.7%)          72   (2.7%)     Gem::BasicSpecification#internal_init
       129   (4.9%)          58   (2.2%)     <top (required)>
        53   (2.0%)          53   (2.0%)     RbConfig.expand
      1697  (64.0%)          52   (2.0%)     <top (required)>
        68   (2.6%)          49   (1.8%)     Gem::Requirement.parse
       183   (6.9%)          48   (1.8%)     <top (required)>
       112   (4.2%)          44   (1.7%)     Gem::Requirement#initialize
       220   (8.3%)          33   (1.2%)     <module:Gem>
       250   (9.4%)          32   (1.2%)     Kernel#require
        96   (3.6%)          30   (1.1%)     Gem::Specification#add_dependency_with_type
        28   (1.1%)          28   (1.1%)     Gem::Specification#date=
        26   (1.0%)          26   (1.0%)     Gem.suffix_regexp
        30   (1.1%)          24   (0.9%)     Gem::Version.correct?
        46   (1.7%)          24   (0.9%)     <class:Specification>
        66   (2.5%)          20   (0.8%)     Gem::Requirement.create
        20   (0.8%)          20   (0.8%)     Gem::Specification#summary=
        60   (2.3%)          18   (0.7%)     Gem::Version.new
        27   (1.0%)          16   (0.6%)     Gem::Util.glob_files_in_dir
        15   (0.6%)          15   (0.6%)     Gem::Specification#add_bindir
        15   (0.6%)          15   (0.6%)     Gem::Specification#authors=
        15   (0.6%)          15   (0.6%)     Gem::PathSupport#expand
        20   (0.8%)          14   (0.5%)     <top (required)>
        42   (1.6%)          13   (0.5%)     Gem::Version#initialize
        21   (0.8%)          13   (0.5%)     <top (required)>

This makes it very hard to see where time is spent as all required files use the same label.

The idea here is to basically do name.gsub('<top (required)>', file), but I'm open to other ways to replace that label.

cc @tenderlove

[casperisfine]

Maybe <require:#{file}> to be somewhat consistent with <module:XXX> etc.

[tmm1]

Wouldn't some sort of strncmp be better here? Does the string match exactly, or is it sometimes contained within?

[casperisfine]

It either match exactly or is trailing:

• <top (required)>
• block in <top (required)>

[casperisfine]

I resolved the comments.

[casperisfine]

Here's what it looks like now:

==================================
  Mode: wall(10)
  Samples: 2602 (57.94% miss rate)
  GC: 669 (25.71%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       402  (15.4%)         402  (15.4%)     (marking)
       716  (27.5%)         314  (12.1%)     Gem::Specification.load
       277  (10.6%)         277  (10.6%)     Gem.already_loaded?
       265  (10.2%)         265  (10.2%)     (sweeping)
       583  (22.4%)         125   (4.8%)     Gem.register_default_spec
        91   (3.5%)          80   (3.1%)     Gem::Specification#files
        70   (2.7%)          70   (2.7%)     Gem::BasicSpecification#internal_init
      1726  (66.3%)          62   (2.4%)     /opt/rubies/2.8.0-dev/lib/ruby/2.8.0/rubygems.rb
       116   (4.5%)          55   (2.1%)     /opt/rubies/2.8.0-dev/lib/ruby/2.8.0/did_you_mean.rb
        55   (2.1%)          55   (2.1%)     RbConfig.expand
        70   (2.7%)          49   (1.9%)     Gem::Requirement.parse
       184   (7.1%)          48   (1.8%)     /opt/rubies/2.8.0-dev/lib/ruby/2.8.0/rubygems/specification.rb
       112   (4.3%)          42   (1.6%)     Gem::Requirement#initialize
       219   (8.4%)          32   (1.2%)     Kernel#require
        31   (1.2%)          31   (1.2%)     Gem::Specification#date=
        31   (1.2%)          30   (1.2%)     Gem.suffix_regexp
       216   (8.3%)          29   (1.1%)     <module:Gem>
        98   (3.8%)          25   (1.0%)     Gem::Specification#add_dependency_with_type
        51   (2.0%)          24   (0.9%)     <class:Specification>
        58   (2.2%)          18   (0.7%)     Gem::Version.new
        40   (1.5%)          18   (0.7%)     Gem::Version#initialize
        18   (0.7%)          18   (0.7%)     Gem::Specification#summary=
        57   (2.2%)          17   (0.7%)     Gem::Requirement.create
        22   (0.8%)          17   (0.7%)     Gem::Version.correct?
        26   (1.0%)          16   (0.6%)     Gem::Util.glob_files_in_dir
        58   (2.2%)          14   (0.5%)     Gem::Dependency#initialize
        27   (1.0%)          14   (0.5%)     /opt/rubies/2.8.0-dev/lib/ruby/2.8.0/rubygems/user_interaction.rb
        13   (0.5%)          13   (0.5%)     Gem::PathSupport#expand
        13   (0.5%)          13   (0.5%)     Gem::Version#prerelease?
        11   (0.4%)          11   (0.4%)     block in <module:Gem>

[casperisfine]

I updated it again, for <require:/opt/rubies/2.8.0-dev/lib/ruby/2.8.0/did_you_mean/spell_checker.rb>.