Performance regression

[crdu...@gmail.com]

I'm seeing a significant performance regression running some JavaScript workloads in an application that embeds V8. There isn't much going on in terms of native code integration in this workload, it's mostly doing some CryptoJS stuff.

Doing a `git bisect` I've isolated the change to this commit: https://chromium.googlesource.com/v8/v8/+/0ff080d1f7f6b1a0fdaedc6e150ac93a8ce962ec

I'm wondering if anyone has any thoughts on this.

- Is anyone else seeing this performance change?
- Would a performance regression have been noticed in regular V8 release testing?

- Does anyone have any thoughts on how to mitigate the performance impact? The changes to the map space in that commit don't appear to have build options to control them, that I can see.

[crdu...@gmail.com]

This specific commit disabled map space by default, and later commits seem to have totally removed map space from the code.

Can anyone provide any details or insights as to what kind of code could be impacted (performance-wise) by this change?

[dinf...@chromium.org]

Hi,

I am not aware of performance regressions with this feature. You can open an issue with a repro so we can take a look at.

Performance is monitored quite heavily with V8 but maybe something slipped through.

Best,

Dominik

[crdu...@gmail.com]

I've submitted a bug with a repro here: https://bugs.chromium.org/p/v8/issues/detail?id=13714

Thanks,

Chris