Fix stale unlog bits for LOS and MarkSweepSpace objects

We now: - Clear the unlog bits for dead LOS objects - Bulk clear the unlog bits for MarkSweepSpace for full heap GC - Set the unlog bits for LOS and MarkSweepSpace objects during trace object This is because we want to ensure the unlog bits are only set for objects that are alive. We do not reset the unlogs bits inside the `ProcessModBuf` work packet because we do not know what objects are alive at that moment in time.
k-sareen · Jul 18, 2024 · 8f6fcd8 · 8f6fcd8
1 parent 059723f
commit 8f6fcd8
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Showing 3 changed files with 24 additions and 3 deletions.
diff --git a/src/policy/largeobjectspace.rs b/src/policy/largeobjectspace.rs
@@ -209,7 +209,9 @@ impl<VM: VMBinding> LargeObjectSpace<VM> {
                 trace!("LOS object {} is being marked now", object);
                 self.treadmill.copy(object, nursery_object);
                 // We just moved the object out of the logical nursery, mark it as unlogged.
-                if nursery_object && self.common.needs_log_bit {
+                // We also set the unlog bit for mature objects to ensure that
+                // any modifications to them are logged
+                if self.common.needs_log_bit {
                     VM::VMObjectModel::GLOBAL_LOG_BIT_SPEC
                         .mark_as_unlogged::<VM>(object, Ordering::SeqCst);
                 }
@@ -228,6 +230,10 @@ impl<VM: VMBinding> LargeObjectSpace<VM> {
         let sweep = |object: ObjectReference| {
             #[cfg(feature = "vo_bit")]
             crate::util::metadata::vo_bit::unset_vo_bit::<VM>(object);
+            if self.common.needs_log_bit {
+                VM::VMObjectModel::GLOBAL_LOG_BIT_SPEC
+                    .clear::<VM>(object, Ordering::SeqCst);
+            }
             self.pr
                 .release_pages(get_super_page(object.to_object_start::<VM>()));
         };

diff --git a/src/policy/marksweepspace/native_ms/global.rs b/src/policy/marksweepspace/native_ms/global.rs
@@ -321,7 +321,7 @@ impl<VM: VMBinding> MarkSweepSpace<VM> {
                 block.set_state(BlockState::Marked);
                 queue.enqueue(object);
                 if self.common.needs_log_bit {
-                    VM::VMObjectModel::GLOBAL_LOG_BIT_SPEC.mark_as_unlogged::<VM>(object, Ordering::SeqCst);
+                    VM::VMObjectModel::GLOBAL_LOG_BIT_SPEC.mark_byte_as_unlogged::<VM>(object, Ordering::SeqCst);
                 }
             }
             object
@@ -337,14 +337,24 @@ impl<VM: VMBinding> MarkSweepSpace<VM> {
         Block::NEXT_BLOCK_TABLE
     }
 
-    pub fn prepare(&mut self, _full_heap: bool) {
+    pub fn prepare(&mut self, full_heap: bool) {
         if let MetadataSpec::OnSide(side) = *VM::VMObjectModel::LOCAL_MARK_BIT_SPEC {
             for chunk in self.chunk_map.all_chunks() {
                 side.bzero_metadata(chunk.start(), Chunk::BYTES);
             }
         } else {
             unimplemented!("in header mark bit is not supported");
         }
+
+        if self.common.needs_log_bit && full_heap {
+            if let MetadataSpec::OnSide(side) = *VM::VMObjectModel::GLOBAL_LOG_BIT_SPEC {
+                for chunk in self.chunk_map.all_chunks() {
+                    side.bzero_metadata(chunk.start(), Chunk::BYTES);
+                }
+            } else {
+                unimplemented!("in header log bit is not supported");
+            }
+        }
     }
 
     pub fn release(&mut self) {

diff --git a/src/util/metadata/log_bit.rs b/src/util/metadata/log_bit.rs
@@ -6,6 +6,11 @@ use std::sync::atomic::Ordering;
 use super::MetadataSpec;
 
 impl VMGlobalLogBitSpec {
+    /// Clear the unlog bit to log object (0 means logged)
+    pub fn clear<VM: VMBinding>(&self, object: ObjectReference, order: Ordering) {
+        self.store_atomic::<VM, u8>(object, 0, None, order)
+    }
+
     /// Mark the log bit as unlogged (1 means unlogged)
     pub fn mark_as_unlogged<VM: VMBinding>(&self, object: ObjectReference, order: Ordering) {
         self.store_atomic::<VM, u8>(object, 1, None, order)