[Webkit-unassigned] [Bug 72404] New: Could save a lot of memory in CharacterData by not always storing a String

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=72404

           Summary: Could save a lot of memory in CharacterData by not
                    always storing a String
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: HTML DOM
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: ojan at chromium.org
                CC: koivisto at iki.fi, simon.fraser at apple.com,
                    arv at chromium.org, eae at chromium.org


Below is the dump just of whitespace text nodes from the HTML spec (string followed by count of that string occurring). If we stored atomic strings in these cases, we'd save a lot of memory. There are also non-whitespace strings that are repeated many times in the spec (e.g. "Unique " is in >30k text nodes). 

For a short whitespace string that conforms to the list of 5 valid space characters in http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#space-character, we could even store it as a single unsigned. Looking at the HTML spec, this is actually by far the common case.

The HTML spec is a bit unique in it's content, but it's certainly a common pattern for sites to have repeated whitespace due to formatting their HTML to be readable.


"

  " 8197
"
   " 4172
"
    " 1052
"
  " 469
"

" 1
"
" 413
"
 " 21
"
     " 3099
"
      " 224
"
       " 497
"
        " 96
"
         " 157
" " 19240
"




  " 52
"



  " 242
"

" 122
"


  " 472
"

   " 6117
"


   " 242
"



   " 4
"


" 17
"

    " 3126
"

     " 1132
"






  " 2
"





  " 7
"

      " 545
"

       " 445
"


     " 78
"

 " 2
"

        " 166
"

         " 140
"

  " 1
"

          " 51
"

           " 26
"

            " 11
"
            " 7
"

              " 2
"

             " 3
"


       " 29
"


    " 6
"          " 1
"     " 1
" 

      " 7
" 

       " 7
"




  " 1
"



  " 7
"   " 2
"
          " 9
"                                                          " 1
"
                                                                            " 1
"


   " 1
"







  " 2
"

  " 2
"

    " 1
"


         " 8
"




" 1
"

  " 1
"



" 1
"


      " 1
" " 1
" " 1
" " 1
" " 1
" " 2
" " 1
" " 3
" " 1
" " 1
"  " 1
" " 2
"  


  " 1
"
           " 8
"   

   " 2
"


" 1

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