diff options
| -rw-r--r-- | runtime/gc/collector/mark_compact.cc | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/runtime/gc/collector/mark_compact.cc b/runtime/gc/collector/mark_compact.cc index 2ef1ec5c9f..618625ec61 100644 --- a/runtime/gc/collector/mark_compact.cc +++ b/runtime/gc/collector/mark_compact.cc @@ -2893,6 +2893,14 @@ void MarkCompact::KernelPreparation() { } // Register the moving space with userfaultfd. RegisterUffd(moving_space_begin, moving_space_register_sz); + // madvise ensures that if any page gets mapped (only possible if some + // thread is reading the page(s) without trying to make sense as we hold + // mutator-lock exclusively) between mremap and uffd-registration, then + // it gets zapped so that the map is empty and ready for userfaults. If + // we could mremap after uffd-registration (like in case of linear-alloc + // space below) then we wouldn't need it. But since we don't register the + // entire space, we can't do that. + madvise(moving_space_begin, moving_space_register_sz, MADV_DONTNEED); } // Prepare linear-alloc for concurrent compaction. for (auto& data : linear_alloc_spaces_data_) { |