No, I think you are making a wrong assumption here. A bug report like that, that pinpoints a line in question and provides observable metrics is the best kind of performance issue that you can file against V8.
Back when I was on the V8 team I would immediately set aside some time to investigate and triage/fix/explain it because stable performance is as important for any VM as correctness.
So don't hesitate to file bugs like that against JavaScript VMs be it V8 or SpiderMonkey. You might be surprised with VM engineers' eagerness to investigate and address performance problems.
> What I want is information.
There are ways to trace optimizations and deoptimizations in V8. Unfortunately nothing as simple to use as JIT-inspector. Most of what V8 has right now is geared towards VM engineers.
I have a tool called IRHydra[1] that can display some information that V8 dumps in a more or less digestible form. It's most useful for performance investigations in the console but to a certain degree works for browser as well (biggest problem for it "multithreading": because V8 dumps part of the information into stdout and as a result it can arrive arbitrary mixed if you have many workers).
No, I think you are making a wrong assumption here. A bug report like that, that pinpoints a line in question and provides observable metrics is the best kind of performance issue that you can file against V8.
Back when I was on the V8 team I would immediately set aside some time to investigate and triage/fix/explain it because stable performance is as important for any VM as correctness.
So don't hesitate to file bugs like that against JavaScript VMs be it V8 or SpiderMonkey. You might be surprised with VM engineers' eagerness to investigate and address performance problems.
> What I want is information.
There are ways to trace optimizations and deoptimizations in V8. Unfortunately nothing as simple to use as JIT-inspector. Most of what V8 has right now is geared towards VM engineers.
I have a tool called IRHydra[1] that can display some information that V8 dumps in a more or less digestible form. It's most useful for performance investigations in the console but to a certain degree works for browser as well (biggest problem for it "multithreading": because V8 dumps part of the information into stdout and as a result it can arrive arbitrary mixed if you have many workers).
[1] http://web.irhydra.googlecode.com/git/hydra.html