Performance improvements

[nebulon42]

This issue is meant to collect discussions about possible performance optimizations. More detailed sub tasks should be opened once identified.

[nebulon42]

About profiling

There is a simple built-in Node.js profiler (https://nodejs.org/en/docs/guides/simple-profiling/). Let's say we want to profile how carto processes osm-carto. We then run node --prof bin/carto -f test.xml path/to/openstreetmap-carto/project.mml from latest master we get a isolate-HASH-v8.log file in the working directory. We then have to post-process said file with node --prof-process isolate-HASH-v8.log > results.txt.

Then I got the following:

[JavaScript]:
   ticks  total  nonlib   name
   1023    6.2%    6.3%  LazyCompile: *[Symbol.replace] native regexp.js:481:31
    643    3.9%    3.9%  LazyCompile: *tree.Filterset.addable path/to/carto/lib/carto/tree/filterset.js:105:44
    324    2.0%    2.0%  Stub: CEntryStub
    305    1.8%    1.9%  Builtin: CallFunction_ReceiverIsAny
    289    1.7%    1.8%  LazyCompile: *RegExpReplace native regexp.js:356:23
    283    1.7%    1.7%  Builtin: Call_ReceiverIsAny
    265    1.6%    1.6%  Stub: StringAddStub
    240    1.5%    1.5%  LazyCompile: *tree.Filterset.cloneWith path/to/carto/lib/carto/tree/filterset.js:59:46
    231    1.4%    1.4%  Stub: FastCloneRegExpStub
    225    1.4%    1.4%  LazyCompile: *replace native string.js:57:23
    212    1.3%    1.3%  Builtin: ToString
    211    1.3%    1.3%  KeyedLoadIC: A keyed load IC from the snapshot {2}
    189    1.1%    1.2%  Builtin: RegExpPrototypeExec
...
 [C++]:
   ticks  total  nonlib   name
    635    3.8%    3.9%  v8::internal::StringReplaceGlobalRegExpWithString(v8::internal::Isolate*, v8::internal::Handle<v8::internal::String>, v8::internal::Handle<v8::internal::JSRegExp>, v8::internal::Handle<v8::internal::String>, v8::internal::Handle<v8::internal::JSObject>)
    550    3.3%    3.4%  v8::internal::Zone::DeleteAll()
    531    3.2%    3.2%  v8::internal::Runtime_StringReplaceGlobalRegExpWithString(int, v8::internal::Object**, v8::internal::Isolate*)
    394    2.4%    2.4%  v8::internal::String::GetFlatContent()
    352    2.1%    2.2%  v8::internal::Object* v8::internal::StringReplaceGlobalAtomRegExpWithString<v8::internal::SeqOneByteString>(v8::internal::Isolate*, v8::internal::Handle<v8::internal::String>, v8::internal::Handle<v8::internal::JSRegExp>, v8::internal::Handle<v8::internal::String>, v8::internal::Handle<v8::internal::JSObject>)
    339    2.1%    2.1%  v8::internal::CompiledReplacement::Compile(v8::internal::Handle<v8::internal::String>, int, int)
    270    1.6%    1.7%  v8::internal::FindStringIndicesDispatch(v8::internal::Isolate*, v8::internal::String*, v8::internal::String*, v8::internal::ZoneList<int>*, unsigned int, v8::internal::Zone*) [clone .constprop.128]
    270    1.6%    1.7%  memchr
    241    1.5%    1.5%  v8::internal::String::ComputeAndSetHash()
    208    1.3%    1.3%  void v8::internal::LookupIterator::Start<false>()
    185    1.1%    1.1%  write
    184    1.1%    1.1%  v8::internal::Zone::New(unsigned long)
    183    1.1%    1.1%  v8::internal::Runtime_KeyedGetProperty(int, v8::internal::Object**, v8::internal::Isolate*)
    165    1.0%    1.0%  v8::internal::StringTable::LookupString(v8::internal::Isolate*, v8::internal::Handle<v8::internal::String>)
    162    1.0%    1.0%  v8::internal::FindTwoByteStringIndices(v8::internal::Vector<unsigned short const>, unsigned short, v8::internal::ZoneList<int>*, unsigned int, v8::internal::Zone*)
...
 [C++ entry points]:
   ticks    cpp   total   name
   3674   44.1%   22.2%  v8::internal::Runtime_StringReplaceGlobalRegExpWithString(int, v8::internal::Object**, v8::internal::Isolate*)
   1607   19.3%    9.7%  v8::internal::Runtime_KeyedGetProperty(int, v8::internal::Object**, v8::internal::Isolate*)
    307    3.7%    1.9%  v8::internal::Runtime_RegExpExec(int, v8::internal::Object**, v8::internal::Isolate*)
    252    3.0%    1.5%  v8::internal::Runtime_ForInEnumerate(int, v8::internal::Object**, v8::internal::Isolate*)
    230    2.8%    1.4%  v8::internal::Runtime_StringAdd(int, v8::internal::Object**, v8::internal::Isolate*)
    194    2.3%    1.2%  v8::internal::Runtime_StoreIC_Miss(int, v8::internal::Object**, v8::internal::Isolate*)
    179    2.2%    1.1%  v8::internal::Runtime_Equal(int, v8::internal::Object**, v8::internal::Isolate*)
    179    2.2%    1.1%  v8::internal::Runtime_CompileLazy(int, v8::internal::Object**, v8::internal::Isolate*)
    169    2.0%    1.0%  v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*)
    155    1.9%    0.9%  v8::internal::Runtime_KeyedStoreIC_Miss(int, v8::internal::Object**, v8::internal::Isolate*)
    139    1.7%    0.8%  v8::internal::Runtime_CompileOptimized_Concurrent(int, v8::internal::Object**, v8::internal::Isolate*)
    124    1.5%    0.8%  v8::internal::Runtime_SetProperty(int, v8::internal::Object**, v8::internal::Isolate*)
    110    1.3%    0.7%  v8::internal::Builtin_FunctionConstructor(int, v8::internal::Object**, v8::internal::Isolate*)
...
 [Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 2.0% are not shown.

   ticks parent  name
   1051    6.4%  UNKNOWN

   1023    6.2%  LazyCompile: *[Symbol.replace] native regexp.js:481:31
   1023  100.0%    LazyCompile: *replace native string.js:57:23
    987   96.5%      LazyCompile: *tree.Filterset.addable path/to/carto/lib/carto/tree/filterset.js:105:44
    987  100.0%        LazyCompile: *tree.Filterset.cloneWith path/to/carto/lib/carto/tree/filterset.js:59:46
    647   65.6%          LazyCompile: *addRules path/to/carto/lib/carto/renderer.js:473:18
    641   99.1%            LazyCompile: *inheritDefinitions path/to/carto/lib/carto/renderer.js:537:28
    336   34.0%          LazyCompile: *foldStyle path/to/carto/lib/carto/renderer.js:611:19
    336  100.0%            LazyCompile: ~render path/to/carto/lib/carto/renderer.js:160:50

    643    3.9%  LazyCompile: *tree.Filterset.addable path/to/carto/lib/carto/tree/filterset.js:105:44
    643  100.0%    LazyCompile: *tree.Filterset.cloneWith path/to/carto/lib/carto/tree/filterset.js:59:46
    439   68.3%      LazyCompile: *addRules path/to/carto/lib/carto/renderer.js:473:18
    426   97.0%        LazyCompile: *inheritDefinitions path/to/carto/lib/carto/renderer.js:537:28
    426  100.0%          LazyCompile: ~render path/to/carto/lib/carto/renderer.js:160:50
    426  100.0%            LazyCompile: ~compile path/to/carto/bin/carto:80:17
     13    3.0%        LazyCompile: ~inheritDefinitions path/to/carto/lib/carto/renderer.js:537:28
     13  100.0%          LazyCompile: ~render path/to/carto/lib/carto/renderer.js:160:50
     13  100.0%            LazyCompile: ~compile path/to/carto/bin/carto:80:17
    202   31.4%      LazyCompile: *foldStyle path/to/carto/lib/carto/renderer.js:611:19
    202  100.0%        LazyCompile: ~render path/to/carto/lib/carto/renderer.js:160:50
    202  100.0%          LazyCompile: ~compile path/to/carto/bin/carto:80:17
    202  100.0%            LazyCompile: ~load path/to/carto/lib/carto/mml.js:19:41
...

(Note: The last time I did this which I didn't document I remember getting some 12% in Filterset.addable or the like)

[StyXman]

I'm baffled. Befuddled. Bewildered.

Let's start with a recent profile:

 [Summary]:
   ticks  total  nonlib   name
  11097   60.1%   65.2%  C++
   5911   32.0%   34.7%  JavaScript
   1453    7.9%          Shared libraries
    163    0.9%    1.0%  GC
      7    0.0%          Unaccounted

 [C++ entry points]:
   ticks    cpp   total   name
   3493   28.5%   18.9%  v8::internal::Runtime_StringReplaceGlobalRegExpWithString(int, v8::internal::Object**, v8::internal::Isolate*)
   2054   16.7%   11.1%  v8::internal::Runtime_Apply(int, v8::internal::Object**, v8::internal::Isolate*)
   1900   15.5%   10.3%  v8::internal::Runtime_KeyedGetProperty(int, v8::internal::Object**, v8::internal::Isolate*)
    892    7.3%    4.8%  v8::internal::Runtime_BoundFunctionGetBindings(int, v8::internal::Object**, v8::internal::Isolate*)

 [JavaScript]:
   ticks  total  nonlib   name
    484    2.6%    2.8%  LazyCompile: *replace native string.js:146:23
    399    2.2%    2.3%  Stub: CEntryStub
    295    1.6%    1.7%  Stub: StringAddStub_CheckNone_NotTenured
    269    1.5%    1.6%  LazyCompile: ~InnerArrayFilter native array.js:891:26
    209    1.1%    1.2%  LazyCompile: ~<anonymous> native v8natives.js:1199:16
    205    1.1%    1.2%  Builtin: ArgumentsAdaptorTrampoline
    163    0.9%    1.0%  LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46

 [Shared libraries]:
   ticks  total  nonlib   name
   1241    6.7%          /usr/bin/nodejs
    205    1.1%          /lib/x86_64-linux-gnu/libc-2.24.so
      3    0.0%          /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.24
      2    0.0%          [vdso]
      2    0.0%          /lib/x86_64-linux-gnu/libm-2.24.so

 [Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 2.0% are not shown.

   ticks parent  name
   1241    6.7%  /usr/bin/nodejs
    537   43.3%    v8::internal::Runtime_Apply(int, v8::internal::Object**, v8::internal::Isolate*)
    534   99.4%      LazyCompile: ~<anonymous> native v8natives.js:1199:16
    534  100.0%        LazyCompile: ~InnerArrayFilter native array.js:891:26
    534  100.0%          LazyCompile: *filter native array.js:915:21
    464   86.9%            LazyCompile: *tree.Variable.ev /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/variable.js:16:17
     55   10.3%            LazyCompile: *tree.Operation.ev /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/operation.js:16:39
     15    2.8%            LazyCompile: ~tree.Variable.ev /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/variable.js:16:17
    355   28.6%    v8::internal::Runtime_StringReplaceGlobalRegExpWithString(int, v8::internal::Object**, v8::internal::Isolate*)
    355  100.0%      LazyCompile: *replace native string.js:146:23
     55   15.5%        LazyCompile: *tree.Filterset.addable /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:105:44
     55  100.0%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     41   74.5%            LazyCompile: *addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     12   21.8%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      2    3.6%            LazyCompile: ~foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     36   10.1%        Handler: 67092480#__default__#line-width {5}
     31   86.1%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     22   71.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      9   29.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      5   13.9%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      3   60.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      2   40.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     36   10.1%        Handler: 67043328#__default__#line-color
     35   97.2%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     24   68.6%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     11   31.4%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      1    2.8%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      1  100.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     32    9.0%        Handler: 67107840#__default__#line-color
     28   87.5%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     18   64.3%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     10   35.7%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      4   12.5%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      2   50.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      2   50.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     30    8.5%        Handler: 67107840#__default__#line-width
     25   83.3%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     15   60.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     10   40.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      5   16.7%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      5  100.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     29    8.2%        Handler: 67107840#__default__#line-color {1}
     25   86.2%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     19   76.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      6   24.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      4   13.8%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      3   75.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      1   25.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     28    7.9%        Handler: 67107840#__default__#line-cap
     25   89.3%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     17   68.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      8   32.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      3   10.7%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      2   66.7%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      1   33.3%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     24    6.8%        Handler: 67076096#access#line-dasharray
     20   83.3%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     10   50.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     10   50.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      4   16.7%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      4  100.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     23    6.5%        Handler: 67106816#__default__#line-width
     19   82.6%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     10   52.6%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      9   47.4%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      4   17.4%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      3   75.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      1   25.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     22    6.2%        Handler: 67092480#__default__#line-color
     17   77.3%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     12   70.6%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      5   29.4%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      5   22.7%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      3   60.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      2   40.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     21    5.9%        Handler: 67076096#access#line-color {1}
     18   85.7%          LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      9   50.0%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      9   50.0%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      3   14.3%          LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      2   66.7%            LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      1   33.3%            LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     12    3.4%        LazyCompile: *tree.Quoted.toString /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/quoted.js:10:23
      7   58.3%          LazyCompile: *DefaultString native runtime.js:657:23
      7  100.0%            LazyCompile: *ConvertToString native array.js:159:25
      2   16.7%          LazyCompile: ~<anonymous> /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/expression.js:23:48
      2  100.0%            LazyCompile: *InnerArrayMap native array.js:1001:23
      2   16.7%          LazyCompile: *DefaultNumber native runtime.js:642:23
      2  100.0%            LazyCompile: *ToPrimitive native runtime.js:528:21
      1    8.3%          LazyCompile: ~tree.Filter.toObject /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filter.js:32:42
      1  100.0%            LazyCompile: ~tree.Filterset.toObject /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:8:45
    109    8.8%    v8::internal::Runtime_KeyedGetProperty(int, v8::internal::Object**, v8::internal::Isolate*)
     70   64.2%      Handler: 67076096#access#line-color
     64   91.4%        LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     44   68.8%          LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     44  100.0%            LazyCompile: *inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
     20   31.3%          LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
     20  100.0%            LazyCompile: render /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:160:50
      6    8.6%        LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      6  100.0%          LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      6  100.0%            LazyCompile: *inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
     23   21.1%      Handler: 67076096#access#line-join
     21   91.3%        LazyCompile: ~tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
     13   61.9%          LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
     13  100.0%            LazyCompile: *inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
      8   38.1%          LazyCompile: *foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      8  100.0%            LazyCompile: render /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:160:50
      2    8.7%        LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      2  100.0%          LazyCompile: ~addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      2  100.0%            LazyCompile: *inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
     11   10.1%      LazyCompile: *tree.Filterset.addable /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:105:44
     11  100.0%        LazyCompile: *tree.Filterset.cloneWith /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/filterset.js:59:46
      9   81.8%          LazyCompile: *addRules /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:473:18
      6   66.7%            LazyCompile: *inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
      3   33.3%            LazyCompile: ~inheritDefinitions /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:537:28
      1    9.1%          LazyCompile: ~foldStyle /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:611:19
      1  100.0%            LazyCompile: render /var/lib/data/mdione/src/system/osm/carto/lib/carto/renderer.js:160:50
      1    9.1%          LazyCompile: *tree.Ruleset.flatten /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/ruleset.js:94:22
      1  100.0%            LazyCompile: *tree.Ruleset.flatten /var/lib/data/mdione/src/system/osm/carto/lib/carto/tree/ruleset.js:94:22

So the plan was to attack the calls to v8::internal::Runtime_StringReplaceGlobalRegExpWithString(). From the bottom up, I understand that most of these calls happen in lib/carto/tree/filterset.js:105:44, tree.Filterset.addable(). Notice that the line number, 105, is the line of where the definition of addable() starts. I can't find any reference about what the 44 means.

But there seem to be no such call in that function; the closest I could find is the regexp in line 110, so I thought: maybe that regexp is taking too long. I replaced the code like this:

    /*
    if (value.match(/^[+-]?[0-9]+(\.[0-9]*)?([e|E][+-]?[0-9]+)?$/)) {
        value = parseFloat(value);
    }
    */
    f = parseFloat(value);
    if (f !== NaN) {
        value = f;
    }

I understand that the code is not equivalent; in particular, if value is like 123abc, with the original code it would retain its string type and original value, while with the new one it would become the float 123.

Guess what: instead of ~18s in my system, now it takes ~4m30s!

I tried to find other, non-sampling profilers to fully profile the script and I can't find any. The closest I got was https://github.com/ralphv/zoran, but it's a 5 commit tool wrote in two days, one in 2015 and another in 2016, and I couldn't make it work with a CLI tool like carto.

As you can see, I'm not a JS developer, so I'm not familiar with its toolchain. I you could provide some pointers on how to actually tackle this, I'll be happy to follow them.

[nebulon42]

I also wanted to get rid of the regex already but that resulted in the weird behaviour you noticed which especially breaks OSM Bright.

I think the problem here is not the regex itself but that the system spends so much time in addable that it is the most important calculation. The filter system of carto is quite complex so I don't understand it fully yet. There is some experimental branch which tries to modify the filter system and also removes the particular function, see #206.

So far I didn't have the need for performance optimizations in JS, so I'm also quite new to the topic. At this point I haven't any specific advice but maybe @tmcw could share some thoughts how he would approach this.

[StyXman]

Well, one thing I learned is that regexps literals are automatically compiled by v8, and probably has a JIT for that too. I also tried caching the results of several toString() and toObject() methods, but nothing made it better and in some cases made it worse, so I also think the JIT is better than us.

I found new ways to profile with chromium (yes, the best JS tool for profiling is in a browser, but it kinda makes sense because of the genesis of the language) and running carto with a recent version of node and its --inspect option. I hope to get some news by the weekend.

[StyXman]

More info:

time ./bin/carto -a 3.0.6 -p=true -b ~/src/projects/osm/osm-carto/project.mml 2>&1 | awk '/^processing/ { layer=$3 }; /^Inheritance/ { print $3, layer }' | sort -n
[...]
113ms amenity-points
120ms amenity-points-poly
292ms landcover
792ms roads-fill
803ms tunnels
967ms bridges
2646ms text-point
2684ms text-poly

real    0m17.062s
user    0m17.513s
sys     0m0.187s

[StyXman]

So chomium/chrome's profiler is as bad as the command line one; that is, it provides no new information, just the same thing graphed in three ways: the bottom up, the top down (slightly more useful) and a flamegraph (ditto).

The latter at least tells us that we're dying of a gazillion of paper cuts:

Zoom to one of the more expensive inheritedDefinitions() / foldStyle() pair:

Zoom to a couple of addRules() and one cloneWith():

So the conclusion so far is: if we think we can gain some processing time, it will have to be by rethinking those 4 functions.

[nebulon42]

Thanks for the time you invested so far! About functions: it was my feeling too that it boils down to those. So we have found that out by research too. The question remains what needs to be done to gain something.

[HolgerJeromin]

I have no knowledge about carto but js optimisation. You loose lot of time in the matching.
Could this code be changed:

if (value.match(/^[+-]?[0-9]+(\.[0-9]*)?([e|E][+-]?[0-9]+)?$/)) {
    value = parseFloat(value);
}

to

let tempvalue = parseFloat(value);
if (!isNaN(tempvalue)) {
    value = tempvalue;
}

@StyXman suggested something like that but forgot that you can not compare NaN with NaN in JS!

NaN !== NaN
true
10 !== NaN
true

Thats why StyXman code dropped the condition and worked with the parseFloat´ed value in any case. No real wonder that carto exploded as it had to handle NaN instead of a string or number.

[nebulon42]

@HolgerJeromin How would you prevent something like that:

var tempvalue = parseFloat('1layer');
if (!isNaN(tempvalue)) {
    console.log('a number');
}

Ref #471 (shows a real world case for that problem)

[HolgerJeromin]

Backed with jsPerf i would do similar code as jQuery has (explanation):

let value = '1layer';
let tempvalue = parseFloat(value);
if (isFinite( tempvalue - value )) {
    value = tempvalue;
}

I hope this does not kill performance again :-)
I could do a blind PR if you like.