clear stale line mark state

Author: tianleq

src/policy/immix/block.rs

@@ -247,7 +247,11 @@ impl Block {
                     if prev_line_is_marked {
                         holes += 1;
                     }
-
+                    // We need to clear the line mark state at least twice in every 128 GC
+                    // otherwise, the line mark state of the last GC will stick around
+                    if line_mark_state > Line::MAX_MARK_STATE - 2 {
+                        line.mark(0);
+                    }
                     #[cfg(feature = "immix_zero_on_release")]
                     crate::util::memory::zero(line.start(), Line::BYTES);
 

src/util/alloc/immix_allocator.rs

@@ -298,6 +298,8 @@ impl<VM: VMBinding> ImmixAllocator<VM> {
                     block.start(),
                     block.end()
                 );
+                // Bulk clear stale line mark state
+                Line::MARK_TABLE.bzero_metadata(block.start(), Block::BYTES);
                 if self.request_for_large {
                     self.large_bump_pointer.cursor = block.start();
                     self.large_bump_pointer.limit = block.end();