My understanding is that until recently (January), V8 (inside Chrome & Edge) made a similar number of calls. The main use is making it so that JIT-generated code is not writable while it is executing. It's an important security measure. V8 switched to a more recent mechanism (memory protection keys) that have been gradually getting support from the various OSes. But IIUC, they switched off the mprotect/VirtualProtect calls unconditionally, and added in the protection key stuff only where supported, which suggests that they left some configurations without any protection at all. SpiderMonkey (in Firefox) has not yet switched to the cheaper mechanism.

I may have some of the details wrong.

https://source.chromium.org/chromium/_/chromium/v8/v8.git/+/...