slow serialization for some cases (happens in Node.js 10)

[kaesonho]

Hi @ericf as we discussed, there might be some case to cause a GC pause,

I'm guessing it's some V8 de-opt we're hitting because the replacer forces V8 to go from native-land to user-land and back. Whereas with JSON.stringify().replace() it can stay in native-land the whole time.
So it's probably causing a serialization/de-serialization of the massive string causing a GC pause.

Now we have data ~500KB to be serialized, and found that some case(typically when the data is complicated and big enough) str.replace takes a very long time after JSON.stringify with replacer

To reproduce it, here's the simple script with the data we have,
We will get rid of it with a gc() or run without replacer, it acts like what you mentioned.
https://drive.google.com/file/d/0B0ZB5_LvayjrRjV0U2hrMGVjMUE/view?usp=sharing
please run node --trace-gc --replacer --issue ./slowserialization.js to reproduce it and see gc solve it with node --trace-gc --expose-gc --replacer --issue --gc ./slowserialization.js

will see when slow serialization happens, there's a lot of sweep and cause time spend.

[41363]     3133 ms: Mark-sweep 331.0 (368.4) -> 327.2 (366.4) MB, 123 ms [last resort gc].
[41363]     3249 ms: Mark-sweep 327.2 (366.4) -> 327.2 (364.4) MB, 116 ms [last resort gc].
[41363]     3361 ms: Mark-sweep 327.2 (364.4) -> 327.2 (364.4) MB, 112 ms [last resort gc].
[41363]     3475 ms: Mark-sweep 327.2 (364.4) -> 327.2 (364.4) MB, 113 ms [last resort gc].
[41363]     3578 ms: Mark-sweep 327.2 (364.4) -> 327.2 (364.4) MB, 103 ms [last resort gc].
[41363]     3676 ms: Mark-sweep 327.2 (364.4) -> 327.2 (364.4) MB, 97 ms [last resort gc].
[41363]     3776 ms: Mark-sweep 327.2 (364.4) -> 327.2 (364.4) MB, 100 ms [last resort gc].

The slow serialization only happens with Node.js 10, 12 won't have that issue.

I don't think that makes sense to fix this only for Node.js 10, but let's discuss here, like can we try something else for handling the function/regexp or make that optional (for our main customer's case, we don't have function and regexp)?

@redonkulus @lingyan @mridgway @Vijar

[caridy]

-1. Engine optimizations solved in node 0.12 should be good enough. I suspect that newer version of node+iojs will improve this even more. I think we should stick to what we have.

[ericf]

With some testing I found that setting the space option to something other than a value that results in no space fixes the issue, e.g.:

JSON.stringify(obj, replacer, 2);

The above has the single-digit ms time in the script as expected/desired, instead of the 100x ms time.