parsing can be extremely slow on macOS

[zackschuster]

the message parsing section of the emailjs test suite runs very slowly, even on an M1 Pro; a single test can take 2+ seconds to complete depending on the size of the payload (up to 5.1mb for a text file). this frequently causes test failures in ci, as parsing can take 10+ seconds to complete in github's environment.

according to profiling of the message parsing tests, the likely cause is this call (note the percentages):

 [C++]:
   ticks  total  nonlib   name
   1654   45.9%   47.2%  T _posix_spawnattr_setflags

obviously this is a very esoteric reaction, and i have no idea how or why such a low-level function is hammering / getting hammered by us; the code has been very stable for years & this slowness is not evident on ubuntu or windows. but, likewise, i've observed this slowness for years as well. i'm hopeful maybe there's just some weird one-line performance cliff? but i would have no idea how to start looking for such a thing.

[andris9]

Can you isolate this by creating a test case for mailparser’s own test suite where parsing an email would take so long? From your example it’s hard to understand what’s going on exactly.

[zackschuster]

profiling test/mail-parser-test.js produces this:

 [C++]:
   ticks  total  nonlib   name
  27835   92.1%   92.5%  T _posix_spawnattr_setflags
   1459    4.8%    4.8%  t __ZN2v88internalL53Builtin_Impl_RelativeTimeFormatPrototypeFormatToPartsENS0_16BuiltinArgumentsEPNS0_7IsolateE
     92    0.3%    0.3%  T __ZN4node10contextify17ContextifyContext15CompileFunctionERKN2v820FunctionCallbackInfoINS2_5ValueEEE

about half of those values can be traced to Out of memory error:

 [C++]:
   ticks  total  nonlib   name
  13519   90.8%   91.3%  T _posix_spawnattr_setflags
    669    4.5%    4.5%  t __ZN2v88internalL53Builtin_Impl_RelativeTimeFormatPrototypeFormatToPartsENS0_16BuiltinArgumentsEPNS0_7IsolateE
    136    0.9%    0.9%  t __ZN4node2fsL4ReadERKN2v820FunctionCallbackInfoINS1_5ValueEEE

now, we're using simpleParser with html parsing disabled, so it's not quite an even comparison, but the behavior is the same so i'm assuming it's a valid clue. also, i have to ask, is a 1mb file size really the soft cap?

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parenthetically, i'm hopeful that https://github.com/nodejs/node/issues/32226 might be the source of this headache. it makes as much sense to me as any other explanation, at least...