On Wed, Jul 05, 2023 at 04:25:21PM -0400, Peter Xu wrote: > There'll still try to be a final fix, am I right? As IIRC allowing page > faults during fork() is one of the major goals of vma lock. Good grief, no. Why would we want to optimise something that happens so rarely? The goal is, as usual, more performance. Satisfying page faults while mmap()/munmap()/mprotect() are happening is worthwhile. Those happen a lot more than fork(). In this case though, there's also a priority-inversion problem that we're trying to solve where process A (high priority) calls mmap() while process B (low priority) is reading /proc/$pid/smaps and now (because rwsems are fair), none of process A's other threads can satisy any page faults until process B is scheduled. Where on earth did you get the idea that we cared even a little bit about the performance of page fault during fork()?
