Add a benchmarking script for string-concat
Use flat_map instead of map.flatten
Use #tr instead of #gsub
Optimize more URL#sanitize_url
Use String#<< instead of String#+=

I just couldn’t believe this but look:

~/jekyll/jekyll#master$ ruby benchmark/string-concat
Calculating -------------------------------------
                  +=      6367 i/100ms
                  <<    128697 i/100ms
-------------------------------------------------
                  +=     1704.3 (±0.6%) i/s -      12734 in   7.472170s
                  <<  4381212.4 (±6.3%) i/s -   21878490 in   5.014899s

WOW.
Add benchmark for hash-fetch

Calculating -------------------------------------
 fetch with no block     66979 i/100ms
  fetch with a block    138257 i/100ms
 brackets with an ||    145792 i/100ms
-------------------------------------------------
 fetch with no block  1255521.2 (±5.2%) i/s -    6296026 in   5.028856s
  fetch with a block  6402972.5 (±8.1%) i/s -   31799110 in   5.002554s
 brackets with an ||  8536511.4 (±8.1%) i/s -   42425472 in   5.005831s
Add a benchmark for symbol-to-proc

Calculating -------------------------------------
               block      5403 i/100ms
              &:to_s      6094 i/100ms
-------------------------------------------------
               block    60023.4 (±5.3%) i/s -     302568 in   5.055537s
              &:to_s    59047.0 (±4.9%) i/s -     298606 in   5.068991s
Add benchmark for yield vs proc.call

Calculating -------------------------------------
               yield     70018 i/100ms
          block.call     42809 i/100ms
-------------------------------------------------
               yield  1099624.2 (±7.3%) i/s -    5531422 in   5.056107s
          block.call   604006.1 (±7.1%) i/s -    3039439 in   5.058794s
Add benchmark for #flat_map

Calculating -------------------------------------
.map.flatten with nested arrays
                          4718 i/100ms
.flat_map with nested arrays
                          6048 i/100ms
.map.flatten with no nested arrays
                          9804 i/100ms
.flat_map with no nested arrays
                          9302 i/100ms
-------------------------------------------------
.map.flatten with nested arrays
                        48118.3 (±4.8%) i/s -     240618 in   5.011942s
.flat_map with nested arrays
                        63838.6 (±5.1%) i/s -     320544 in   5.034864s
.map.flatten with no nested arrays
                       104879.3 (±4.4%) i/s -     529416 in   5.057802s
.flat_map with no nested arrays
                        99935.3 (±6.6%) i/s -     502308 in   5.049506s
Add benchmark around string replacement.

Calculating -------------------------------------
                 #tr     62416 i/100ms
               #gsub     33750 i/100ms
              #gsub!     29695 i/100ms
                #sub     60774 i/100ms
               #sub!     64955 i/100ms
-------------------------------------------------
                 #tr   989348.8 (±5.0%) i/s -    4993280 in   5.060836s
               #gsub   422892.9 (±4.3%) i/s -    2126250 in   5.037741s
              #gsub!   364115.6 (±4.0%) i/s -    1841090 in   5.064496s
                #sub   964336.6 (±4.4%) i/s -    4861920 in   5.051775s
               #sub!  1016598.5 (±4.7%) i/s -    5131445 in   5.058987s
Add benchmark for sequential assignment.

Calculating -------------------------------------
 parallel assignment    126425 i/100ms
multi-line assignment
                        136492 i/100ms
-------------------------------------------------
 parallel assignment  6382145.2 (±10.1%) i/s -   31606250 in   5.006184s
multi-line assignment
                      9281041.8 (±11.7%) i/s -   45724820 in   5.001599s
Replace costly Hash#fetch with arity=2 with arity=1 + block.
Have to go back on all these...
:frowning:
Merge pull request #3022 from jekyll/perf
Update history to reflect merge of #3022 [ci skip]