mmtk/plan/generational/
barrier.rs

1//! Generational read/write barrier implementations.
2
3use crate::plan::barriers::BarrierSemantics;
4use crate::plan::PlanTraceObject;
5use crate::plan::VectorQueue;
6use crate::policy::gc_work::DEFAULT_TRACE;
7use crate::scheduler::WorkBucketStage;
8use crate::util::constants::BYTES_IN_INT;
9use crate::util::*;
10use crate::vm::slot::MemorySlice;
11use crate::vm::VMBinding;
12use crate::MMTK;
13
14use super::gc_work::GenNurseryProcessEdges;
15use super::gc_work::ProcessModBuf;
16use super::gc_work::ProcessRegionModBuf;
17use super::global::GenerationalPlanExt;
18
19pub struct GenObjectBarrierSemantics<
20    VM: VMBinding,
21    P: GenerationalPlanExt<VM> + PlanTraceObject<VM>,
22> {
23    /// MMTk instance
24    mmtk: &'static MMTK<VM>,
25    /// Generational plan
26    plan: &'static P,
27    /// Object modbuf. Contains a list of objects that may contain pointers to the nursery space.
28    modbuf: VectorQueue<ObjectReference>,
29    /// Array-copy modbuf. Contains a list of sub-arrays or array slices that may contain pointers to the nursery space.
30    region_modbuf: VectorQueue<VM::VMMemorySlice>,
31}
32
33impl<VM: VMBinding, P: GenerationalPlanExt<VM> + PlanTraceObject<VM>>
34    GenObjectBarrierSemantics<VM, P>
35{
36    pub fn new(mmtk: &'static MMTK<VM>, plan: &'static P) -> Self {
37        Self {
38            mmtk,
39            plan,
40            modbuf: VectorQueue::new(),
41            region_modbuf: VectorQueue::new(),
42        }
43    }
44
45    fn flush_modbuf(&mut self) {
46        let buf = self.modbuf.take();
47        if !buf.is_empty() {
48            self.mmtk.scheduler.work_buckets[WorkBucketStage::Closure]
49                .add(ProcessModBuf::<GenNurseryProcessEdges<VM, P, DEFAULT_TRACE>>::new(buf));
50        }
51    }
52
53    fn flush_region_modbuf(&mut self) {
54        let buf = self.region_modbuf.take();
55        if !buf.is_empty() {
56            debug_assert!(!buf.is_empty());
57            self.mmtk.scheduler.work_buckets[WorkBucketStage::Closure].add(ProcessRegionModBuf::<
58                GenNurseryProcessEdges<VM, P, DEFAULT_TRACE>,
59            >::new(buf));
60        }
61    }
62}
63
64impl<VM: VMBinding, P: GenerationalPlanExt<VM> + PlanTraceObject<VM>> BarrierSemantics
65    for GenObjectBarrierSemantics<VM, P>
66{
67    type VM = VM;
68
69    fn flush(&mut self) {
70        self.flush_modbuf();
71        self.flush_region_modbuf();
72    }
73
74    fn object_reference_write_slow(
75        &mut self,
76        src: ObjectReference,
77        _slot: VM::VMSlot,
78        _target: Option<ObjectReference>,
79    ) {
80        // enqueue the object
81        self.modbuf.push(src);
82        self.modbuf.is_full().then(|| self.flush_modbuf());
83    }
84
85    fn memory_region_copy_slow(&mut self, _src: VM::VMMemorySlice, dst: VM::VMMemorySlice) {
86        // Check if the destination object/slice is in nursery space.
87        let dst_in_nursery = match dst.object() {
88            Some(obj) => self.plan.is_object_in_nursery(obj),
89            None => self.plan.is_address_in_nursery(dst.start()),
90        };
91        // Only enqueue array slices in mature spaces
92        if !dst_in_nursery {
93            // enqueue
94            debug_assert_eq!(
95                dst.bytes() & (BYTES_IN_INT - 1),
96                0,
97                "bytes should be a multiple of 32-bit words"
98            );
99            self.region_modbuf.push(dst);
100            self.region_modbuf
101                .is_full()
102                .then(|| self.flush_region_modbuf());
103        }
104    }
105
106    fn object_probable_write_slow(&mut self, obj: ObjectReference) {
107        // enqueue the object
108        self.modbuf.push(obj);
109        self.modbuf.is_full().then(|| self.flush_modbuf());
110    }
111}
mmtk/plan/generational/barrier.rs

mmtk/plan/generational/
barrier.rs
