Fix

Author: qinsoon

Cargo.toml

@@ -152,6 +152,11 @@ object_pinning = []
 # Disable any object copying in Immix. This makes Immix a non-moving policy.
 immix_non_moving = []
 
+# Disable any object copying in nursery GC for Sticky Immix while allowing other kinds of copying.
+# `immix_non_moving` disables all kinds of copying in Immix, so this feature is not needed
+# if `immix_non_moving` is in use.
+sticky_immix_non_moving_nursery = []
+
 # Turn on stress copying for Immix. This is a debug feature to test copying for Immix plans.
 immix_stress_copying = []
 # Reduce block size for ImmixSpace.  This mitigates fragmentation when defrag is disabled.

src/plan/sticky/immix/global.rs

@@ -262,7 +262,7 @@ impl<VM: VMBinding> crate::plan::generational::global::GenerationalPlanExt<VM> f
                     self.immix
                         .immix_space
                         .trace_object_without_moving(queue, object)
-                } else if self.immix.immix_space.is_nursery_copy_enabled() {
+                } else if self.immix.immix_space.prefer_copy_on_nursery_gc() {
                     let ret = self.immix.immix_space.trace_object_with_opportunistic_copy(
                         queue,
                         object,

src/policy/immix/defrag.rs

@@ -63,20 +63,23 @@ impl Defrag {
     }
 
     /// Determine whether the current GC should do defragmentation.
+    #[allow(clippy::too_many_arguments)]
     pub fn decide_whether_to_defrag(
         &self,
+        defrag_enabled: bool,
         emergency_collection: bool,
         collect_whole_heap: bool,
         collection_attempts: usize,
         user_triggered: bool,
         exhausted_reusable_space: bool,
         full_heap_system_gc: bool,
     ) {
-        let in_defrag = emergency_collection
-            || (collection_attempts > 1)
-            || !exhausted_reusable_space
-            || super::STRESS_DEFRAG
-            || (collect_whole_heap && user_triggered && full_heap_system_gc);
+        let in_defrag = defrag_enabled
+            && (emergency_collection
+                || (collection_attempts > 1)
+                || !exhausted_reusable_space
+                || super::STRESS_DEFRAG
+                || (collect_whole_heap && user_triggered && full_heap_system_gc));
         info!("Defrag: {}", in_defrag);
         probe!(mmtk, immix_defrag, in_defrag);
         self.in_defrag_collection

src/policy/immix/immixspace.rs

@@ -124,7 +124,7 @@ impl<VM: VMBinding> SFT for ImmixSpace<VM> {
         VM::VMObjectModel::LOCAL_PINNING_BIT_SPEC.is_object_pinned::<VM>(object)
     }
     fn is_movable(&self) -> bool {
-        !self.is_defrag_enabled() && !self.is_nursery_copy_enabled()
+        !self.space_args.never_move_objects
     }
 
     #[cfg(feature = "sanity")]
@@ -369,10 +369,8 @@ impl<VM: VMBinding> ImmixSpace<VM> {
         user_triggered_collection: bool,
         full_heap_system_gc: bool,
     ) -> bool {
-        if !self.is_defrag_enabled() {
-            return false;
-        }
         self.defrag.decide_whether_to_defrag(
+            self.is_defrag_enabled(),
             emergency_collection,
             collect_whole_heap,
             collection_attempts,
@@ -856,7 +854,7 @@ impl<VM: VMBinding> ImmixSpace<VM> {
     }
 
     pub(crate) fn is_nursery_copy_enabled(&self) -> bool {
-        !self.space_args.never_move_objects
+        !self.space_args.never_move_objects && !cfg!(feature = "sticky_immix_non_moving_nursery")
     }
 
     pub(crate) fn is_defrag_enabled(&self) -> bool {
@@ -896,7 +894,7 @@ impl<VM: VMBinding> GCWork<VM> for PrepareBlockState<VM> {
                 continue;
             }
             // Check if this block needs to be defragmented.
-            let is_defrag_source = if self.space.space_args.never_move_objects {
+            let is_defrag_source = if !self.space.is_defrag_enabled() {
                 // Do not set any block as defrag source if defrag is disabled.
                 false
             } else if super::DEFRAG_EVERY_BLOCK {