It explains why JSON parsing doesn't perform well, but doesn't explain the original benchmark results. Would be great to get a comment from @mraleph or the other V8 guys on that.

Speaking about GC behavior of other benchmarks:

1) one with Buffers is also causing mark-sweep/compact pauses (7-15ms each) because Buffer constructor calls AdjustAmountOfExternalAllocatedMemory which triggers full gc cycle if it thinks that too much memory is held outside V8.

2) GCs in string based benchmark are mainly scavenges taking 0 ms plus < 10 full collections taking <6ms each on my desktop.

That is all I can say. V8 GC is performing well here from my point of view.

I just found out the same. So I guess it must be some intra-VM data shifting? Anyway, I'll update my posting accordingly.

I don't know node.js well enough to even make a guess here. Somebody needs to profile it.

Updating your post sounds like a nice idea. It created a lot of confusion among developers.

Updated!