Files
OxideJS-New/crates/oxide_vm/src/session_gc.rs
T

964 lines
37 KiB
Rust

use std::collections::{HashMap, HashSet};
use std::mem::size_of;
use std::time::Instant;
use oxide_kernel::vm_debug;
use oxide_types::object::{JsObject, JsString, PropMetaEntry};
use oxide_types::value::JsValue;
use rustc_hash::FxBuildHasher;
use crate::builtins::{array_buffer, data_view, map, regexp, set, typed_array};
use crate::vm::Vm;
pub struct SessionGc {
pub total_collections: u64,
pub total_bytes_freed: u64,
pub total_objects_scanned: u64,
pub total_objects_live: u64,
pub total_objects_dead: u64,
pub last_collection_objects_scanned: u64,
pub last_collection_objects_live: u64,
pub last_collection_objects_dead: u64,
pub last_collection_bytes_freed: u64,
pub last_collection_duration_us: u64,
pub max_collection_duration_us: u64,
pub min_collection_duration_us: u64,
pub(crate) mark_stack: Vec<*mut JsObject>,
pub(crate) live_strings: HashSet<*mut JsString, FxBuildHasher>,
}
impl SessionGc {
pub fn new() -> Self {
Self::default()
}
}
impl SessionGc {
pub(crate) fn clear_all_marks(&mut self, vm: &mut Vm) {
for &ptr in &vm.gc_state.session_object_ptrs {
if ptr.is_null() {
continue;
}
// SAFETY: ptrs in session_object_ptrs come only from `session_epoch.alloc` in
// `promote_object_inner`, and are valid while the arena is alive.
unsafe { (*ptr).set_gc_mark(false) };
}
}
fn object_edges(obj: &JsObject) -> Vec<JsValue> {
let mut edges = Vec::new();
if let Some(props) = obj.hash_props_vec() {
edges.extend(props.iter().copied().filter(|val| val.is_object()));
}
if let Some(meta) = obj.prop_meta_vec() {
for entry in meta.iter().flatten() {
if entry.get.is_object() {
edges.push(entry.get);
}
if entry.set.is_object() {
edges.push(entry.set);
}
}
}
if obj.proto().is_object() {
edges.push(obj.proto());
}
if obj.captured_this().is_object() {
edges.push(obj.captured_this());
}
if obj.home_object().is_object() {
edges.push(obj.home_object());
}
if obj.is_map() {
edges.extend(map::map_native_edges(obj));
}
if obj.is_set() {
edges.extend(set::set_native_edges(obj));
}
if obj.is_typed_array_obj() {
edges.extend(typed_array::typed_array_native_edges(obj));
}
if obj.is_data_view_obj() {
edges.extend(data_view::data_view_native_edges(obj));
}
edges
}
/// Record session-string values held directly by `obj` into `live`. JsStrings hold no GC
/// references, so "reaching" a string IS marking it — there is no string DFS stack. Permanent
/// strings are also recorded here harmlessly; the sweep only iterates `session_string_ptrs`, so
/// non-session pointers in `live` are simply never consulted.
fn record_object_string_edges(live: &mut HashSet<*mut JsString, FxBuildHasher>, obj: &JsObject) {
if let Some(props) = obj.hash_props_vec() {
for value in props.iter() {
if value.is_string() {
live.insert(value.as_string_ptr_mut());
}
}
}
if obj.captured_this().is_string() {
live.insert(obj.captured_this().as_string_ptr_mut());
}
if obj.home_object().is_string() {
live.insert(obj.home_object().as_string_ptr_mut());
}
if obj.is_map() {
for value in map::map_native_edges(obj) {
if value.is_string() {
live.insert(value.as_string_ptr_mut());
}
}
}
if obj.is_set() {
for value in set::set_native_edges(obj) {
if value.is_string() {
live.insert(value.as_string_ptr_mut());
}
}
}
}
pub(crate) fn mark(&mut self, vm: &Vm) {
let mut seeds = Vec::new();
let mut string_seeds: Vec<*mut JsString> = Vec::new();
vm.for_each_root(|root| {
if root.is_object() {
seeds.push(root.as_js_object_ptr());
} else if root.is_string() {
string_seeds.push(root.as_string_ptr_mut());
}
});
let Self {
mark_stack: stack,
live_strings,
..
} = self;
stack.clear();
live_strings.clear();
for ptr in string_seeds {
if !ptr.is_null() {
live_strings.insert(ptr);
}
}
for ptr in seeds {
if ptr.is_null() {
continue;
}
if vm.is_session_ptr(ptr) {
stack.push(ptr);
continue;
}
// SAFETY: object roots are produced by VM-owned fields and builtin objects.
let obj = unsafe { &*ptr };
Self::record_object_string_edges(live_strings, obj);
for edge in Self::object_edges(obj) {
if edge.is_object() {
let edge_ptr = edge.as_js_object_ptr();
if vm.is_session_ptr(edge_ptr) {
stack.push(edge_ptr);
}
}
}
}
while let Some(ptr) = stack.pop() {
if ptr.is_null() {
continue;
}
// SAFETY: ptr was discovered from a root/session edge and session root checks require
// this to be a valid session object pointer.
unsafe {
let obj = &mut *ptr;
if obj.is_gc_marked() {
continue;
}
obj.set_gc_mark(true);
Self::record_object_string_edges(live_strings, obj);
let edges = Self::object_edges(obj);
for edge in edges {
if !edge.is_object() {
continue;
}
let child_ptr = edge.as_js_object_ptr();
if vm.is_session_ptr(child_ptr) {
stack.push(child_ptr);
}
}
}
}
}
pub(crate) fn drop_object_heap_data(obj_ptr: *mut JsObject, require_session: bool) -> u64 {
if obj_ptr.is_null() {
return 0;
}
// SAFETY: `obj_ptr` is verified before calling this helper and points to a session object
// owned by the VM session arena. We only reconstruct Boxes that were allocated in
// `JsObject::ensure_hash_props`/`ensure_prop_meta` and then drop them once here.
unsafe {
let obj = &mut *obj_ptr;
if require_session {
debug_assert!(obj.is_session_epoch());
}
let mut freed_bytes = 0u64;
let hash_ptr = obj.hash_props_raw() as *mut Vec<JsValue>;
if !hash_ptr.is_null() {
let vec = Box::from_raw(hash_ptr);
freed_bytes += size_of::<Vec<JsValue>>() as u64 + (vec.capacity() * size_of::<JsValue>()) as u64;
std::mem::drop(vec);
}
let meta_ptr = obj.prop_meta_raw() as *mut Vec<Option<PropMetaEntry>>;
if !meta_ptr.is_null() {
let vec = Box::from_raw(meta_ptr);
freed_bytes += size_of::<Vec<Option<PropMetaEntry>>>() as u64
+ (vec.capacity() * size_of::<Option<PropMetaEntry>>()) as u64;
std::mem::drop(vec);
}
freed_bytes += map::drop_map_native(obj);
freed_bytes += set::drop_set_native(obj);
freed_bytes += array_buffer::drop_array_buffer_native(obj);
freed_bytes += regexp::drop_regexp_native(obj);
freed_bytes += typed_array::drop_typed_array_native(obj);
freed_bytes += data_view::drop_data_view_native(obj);
freed_bytes
}
}
fn drop_session_object_heap_data(obj_ptr: *mut JsObject) -> u64 {
Self::drop_object_heap_data(obj_ptr, true)
}
fn drop_dead_session_object(obj_ptr: *mut JsObject) -> u64 {
Self::drop_session_object_heap_data(obj_ptr) + size_of::<JsObject>() as u64
}
/// Drop a dead session `JsString` (allocated by `Vm::new_string` via `Box::into_raw`),
/// returning the bytes freed. Mirrors `Vm::free_session_string_heap_data`'s drop, but applied
/// selectively to a single dead pointer.
///
/// SAFETY: `ptr` must be a non-null pointer produced by `Box::into_raw(Box::new(JsString))` in
/// `Vm::new_string`, still present in `session_string_ptrs`, and dropped exactly once.
unsafe fn drop_dead_session_string(ptr: *mut JsString) -> u64 {
let bytes = (size_of::<JsString>() + (*ptr).len()) as u64;
drop(Box::from_raw(ptr));
bytes
}
pub(crate) fn sweep(&mut self, vm: &mut Vm) -> u64 {
let old_ptrs = std::mem::take(&mut vm.gc_state.session_object_ptrs);
let mut forwarding = std::mem::take(&mut vm.gc_state.forwarding);
let new_arena = bumpalo::Bump::new();
let mut survivors = 0u64;
let mut dead = 0u64;
let mut freed_bytes = 0u64;
for old_ptr in old_ptrs {
if old_ptr.is_null() {
continue;
}
// SAFETY: old_ptr comes from session_arena promotions and still points into the old
// session arena while sweep runs.
let is_live = unsafe { (*old_ptr).is_gc_marked() };
if is_live {
survivors += 1;
let old_ref = unsafe { &*old_ptr };
let clone = old_ref.clone_for_session_epoch();
let new_ptr = new_arena.alloc(clone) as *mut JsObject;
let new_ref = unsafe { &mut *new_ptr };
if old_ref.is_map() {
map::clone_map_native_with_rewrite(old_ref, new_ref, |value| value);
} else if old_ref.is_set() {
set::clone_set_native_with_rewrite(old_ref, new_ref, |value| value);
} else if old_ref.is_array_buffer_obj() {
array_buffer::clone_array_buffer_native(old_ref, new_ref);
} else if old_ref.is_typed_array_obj() {
typed_array::clone_typed_array_native_with_rewrite(old_ref, new_ref, |value| value);
} else if old_ref.is_data_view_obj() {
data_view::clone_data_view_native_with_rewrite(old_ref, new_ref, |value| value);
}
forwarding.insert(old_ptr, new_ptr);
freed_bytes += Self::drop_session_object_heap_data(old_ptr);
} else {
dead += 1;
freed_bytes += Self::drop_dead_session_object(old_ptr);
}
}
for &dst in forwarding.values() {
// SAFETY: all pointers in forwarding are newly allocated and initialized objects.
let obj = unsafe { &mut *dst };
obj.rewrite_object_values(|value| {
if value.is_object() {
let ptr = value.as_js_object_ptr();
if let Some(&fwd) = forwarding.get(&ptr) {
return JsValue::from_js_object(fwd);
}
}
value
});
if obj.is_map() {
map::rewrite_map_native(obj, |value| rewrite_forwarded_value(value, &forwarding));
} else if obj.is_set() {
set::rewrite_set_native(obj, |value| rewrite_forwarded_value(value, &forwarding));
} else if obj.is_typed_array_obj() {
typed_array::rewrite_typed_array_native(obj, |value| rewrite_forwarded_value(value, &forwarding));
} else if obj.is_data_view_obj() {
data_view::rewrite_data_view_native(obj, |value| rewrite_forwarded_value(value, &forwarding));
}
}
rewrite_vm_roots(vm, &forwarding);
vm.gc_state.session_object_ptrs = forwarding.values().copied().collect();
forwarding.clear();
vm.gc_state.forwarding = forwarding;
vm.gc_state.session_epoch = new_arena;
vm.gc_state.session_bytes_allocated = vm.gc_state.session_object_ptrs.len() * size_of::<JsObject>();
self.clear_all_marks(vm);
let total_ptrs = survivors + dead;
if total_ptrs > 0 {
if dead == 0 {
vm_debug!("[GC] sweep phase -> no objects collected ({} live, {} dead)", survivors, dead);
} else {
vm_debug!(
"[GC] sweep phase: {} scanned, {} live, {} dead, {} bytes",
total_ptrs,
survivors,
dead,
freed_bytes
);
}
}
self.total_bytes_freed += freed_bytes;
self.total_objects_scanned += total_ptrs;
self.total_objects_live += survivors;
self.total_objects_dead += dead;
self.last_collection_objects_scanned = total_ptrs;
self.last_collection_objects_live = survivors;
self.last_collection_objects_dead = dead;
self.last_collection_bytes_freed = freed_bytes;
freed_bytes
}
/// Sweep session `JsString`s: keep the pointers recorded live during `mark()`, drop the rest
/// via `Box::from_raw`. Live strings are NOT moved — Box addresses are stable — so no forwarding
/// map and no root-pointer rewriting are needed. Run after the object sweep (which resets
/// `session_bytes_allocated` to object-only), re-adding surviving string bytes. Returns the
/// bytes freed.
pub(crate) fn sweep_session_strings(&mut self, vm: &mut Vm) -> u64 {
let old = std::mem::take(&mut vm.gc_state.session_string_ptrs);
let mut freed = 0u64;
let mut live_bytes = 0usize;
let mut live = Vec::with_capacity(old.len());
for ptr in old {
if ptr.is_null() {
continue;
}
if self.live_strings.contains(&ptr) {
// Survivor — address unchanged, no rewrite needed.
// SAFETY: ptr is a live session-string box still owned by the VM.
live_bytes += unsafe { size_of::<JsString>() + (*ptr).len() };
live.push(ptr);
} else {
// SAFETY: ptr is in session_string_ptrs but not reachable; drop exactly once.
freed += unsafe { Self::drop_dead_session_string(ptr) };
}
}
vm.gc_state.session_string_ptrs = live;
vm.gc_state.session_bytes_allocated = vm.gc_state.session_bytes_allocated.saturating_add(live_bytes);
self.total_bytes_freed = self.total_bytes_freed.saturating_add(freed);
self.last_collection_bytes_freed = self.last_collection_bytes_freed.saturating_add(freed);
freed
}
pub(crate) fn should_collect(&self, vm: &Vm) -> bool {
(!vm.gc_state.session_object_ptrs.is_empty() || !vm.gc_state.session_string_ptrs.is_empty())
&& vm.gc_state.session_bytes_allocated >= vm.kernel_core().config().session_gc_threshold
}
pub(crate) fn collect(&mut self, vm: &mut Vm) {
let start = Instant::now();
self.mark(vm);
let mut freed_bytes = self.sweep(vm);
freed_bytes += self.sweep_session_strings(vm);
let elapsed = start.elapsed();
self.total_collections += 1;
self.last_collection_duration_us = elapsed.as_micros() as u64;
self.max_collection_duration_us = self.max_collection_duration_us.max(self.last_collection_duration_us);
self.min_collection_duration_us = self.min_collection_duration_us.min(self.last_collection_duration_us);
if freed_bytes > 0 || self.total_collections % 100 == 0 {
vm_debug!("{}", self.stats_summary());
}
}
pub(crate) fn maybe_collect(&mut self, vm: &mut Vm) {
if self.should_collect(vm) {
self.collect(vm);
}
}
pub(crate) fn stats_summary(&self) -> String {
format!(
"[GC] collection #{}: {} scanned, {} live, {} dead, {} freed, {}μs",
self.total_collections,
self.last_collection_objects_scanned,
self.last_collection_objects_live,
self.last_collection_objects_dead,
self.last_collection_bytes_freed,
self.last_collection_duration_us
)
}
}
impl Default for SessionGc {
fn default() -> Self {
Self {
total_collections: 0,
total_bytes_freed: 0,
total_objects_scanned: 0,
total_objects_live: 0,
total_objects_dead: 0,
last_collection_objects_scanned: 0,
last_collection_objects_live: 0,
last_collection_objects_dead: 0,
last_collection_bytes_freed: 0,
last_collection_duration_us: 0,
max_collection_duration_us: 0,
min_collection_duration_us: u64::MAX,
mark_stack: Vec::new(),
live_strings: HashSet::default(),
}
}
}
fn rewrite_forwarded_value(
value: JsValue, forwarding: &HashMap<*mut JsObject, *mut JsObject, FxBuildHasher>,
) -> JsValue {
if !value.is_object() {
return value;
}
forwarding
.get(&value.as_js_object_ptr())
.map(|&ptr| JsValue::from_js_object(ptr))
.unwrap_or(value)
}
fn rewrite_vm_roots(vm: &mut Vm, forwarding: &HashMap<*mut JsObject, *mut JsObject, FxBuildHasher>) {
for value in &mut vm.regs {
*value = rewrite_forwarded_value(*value, forwarding);
}
for value in &mut vm.save_stack {
*value = rewrite_forwarded_value(*value, forwarding);
}
for frame in &mut vm.frames {
frame.saved_this = rewrite_forwarded_value(frame.saved_this, forwarding);
frame.saved_new_target = rewrite_forwarded_value(frame.saved_new_target, forwarding);
frame.callee = rewrite_forwarded_value(frame.callee, forwarding);
frame.constructed_this = frame.constructed_this.map(|value| rewrite_forwarded_value(value, forwarding));
}
vm.exception_value = vm.exception_value.map(|value| rewrite_forwarded_value(value, forwarding));
vm.pending_exception = vm.pending_exception.map(|value| rewrite_forwarded_value(value, forwarding));
for value in &mut vm.iters.for_of_iters {
*value = rewrite_forwarded_value(*value, forwarding);
}
vm.iters.last_for_of_result = rewrite_forwarded_value(vm.iters.last_for_of_result, forwarding);
// Converted immutables are non-session (scalars + perm-strings) — not rewritten.
for iter in &mut vm.iters.for_in_iters {
if iter.is_null() {
continue;
}
// SAFETY: for_in_iters stores live iterator pointers owned by the current VM epoch.
unsafe {
for value in (*(*iter)).keys.iter_mut() {
*value = rewrite_forwarded_value(*value, forwarding);
}
}
}
let global_ptr = vm.session.global_object().as_ptr() as *mut JsObject;
if !global_ptr.is_null() {
// SAFETY: KernelSession owns global_object for the VM lifetime.
unsafe {
(*global_ptr).rewrite_object_values(|value| rewrite_forwarded_value(value, forwarding));
}
}
}
#[cfg(test)]
mod tests {
use oxide_kernel::kernel::{KernelConfig, KernelCore};
use oxide_types::object::JsObject;
use super::*;
use crate::builtins::{array_buffer, data_view, map, set, typed_array};
use crate::vm::{CallFrame, FrameContinuation};
use oxide_runtime_api::NativeResult;
fn plain_object(vm: &mut Vm) -> *mut JsObject {
let proto_ptr = vm.session.builtin_world().object_proto.as_ptr() as *mut JsObject;
vm.epoch.alloc(JsObject::new_empty(
oxide_kernel::shape_forge::EMPTY_SHAPE_ID,
JsValue::from_js_object(proto_ptr),
))
}
fn has_ptr(roots: &[JsValue], ptr: *mut JsObject) -> bool {
roots
.iter()
.any(|value| value.is_object() && std::ptr::eq(value.as_js_object_ptr(), ptr))
}
#[test]
fn gc_roots_contains_registers_frames_and_root_roots() {
let mut vm = Vm::new();
let root = plain_object(&mut vm);
let frame_obj = plain_object(&mut vm);
let saved_this = plain_object(&mut vm);
let child = plain_object(&mut vm);
unsafe {
(*root).set_prop_at(0, JsValue::from_js_object(child));
}
let root_session = vm.promote_object(root);
let frame_session = vm.promote_object(frame_obj);
let this_session = vm.promote_object(saved_this);
let child_session = vm.promote_object(child);
vm.regs[0] = JsValue::from_js_object(root_session);
vm.frames.push(CallFrame {
return_addr: 0,
function_name: 0,
caller_reg_limit: 1,
saved_reg_offset: 0,
saved_this: JsValue::from_js_object(this_session),
saved_new_target: JsValue::from_js_object(child_session),
callee: JsValue::from_js_object(child_session),
construct_result_reg: None,
constructed_this: Some(JsValue::from_js_object(child_session)),
is_derived_constructor: false,
continuation: FrameContinuation::None,
});
vm.save_stack.push(JsValue::from_js_object(frame_session));
vm.regs[1] = JsValue::from_js_object(child_session);
vm.exception_value = Some(JsValue::from_js_object(root_session));
vm.pending_exception = Some(JsValue::from_js_object(child_session));
vm.iters.for_of_iters.push(JsValue::from_js_object(child_session));
vm.iters.last_for_of_result = JsValue::from_js_object(root_session);
let mut roots = Vec::new();
vm.for_each_root(|v| roots.push(v));
assert!(has_ptr(&roots, root_session));
assert!(has_ptr(&roots, frame_session));
assert!(has_ptr(&roots, this_session));
assert!(has_ptr(&roots, child_session));
assert!(has_ptr(&roots, vm.session.global_object().as_ptr() as *mut JsObject));
assert!(!roots.is_empty());
assert!(roots.contains(&JsValue::from_js_object(root_session)));
assert_eq!(vm.exception_value, Some(JsValue::from_js_object(root_session)));
}
#[test]
fn mark_phase_reaches_cycles_and_unreachable_are_unmarked() {
let mut vm = Vm::new();
let root = plain_object(&mut vm);
let reachable = plain_object(&mut vm);
let unreachable = plain_object(&mut vm);
unsafe {
(*root).set_prop_at(0, JsValue::from_js_object(reachable));
(*reachable).set_prop_at(0, JsValue::from_js_object(root));
}
let root_session = vm.promote_object(root);
let reachable_session = unsafe { (*root_session).get_prop_at(0).as_js_object_ptr() };
let unreachable_session = vm.promote_object(unreachable);
vm.regs[0] = JsValue::from_js_object(root_session);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.mark(&vm);
vm.gc_state.session_gc = gc;
assert!(unsafe { (*root_session).is_gc_marked() });
assert!(unsafe { (*reachable_session).is_gc_marked() });
assert!(!unsafe { (*unreachable_session).is_gc_marked() });
assert_ne!(unreachable_session, root_session);
}
#[test]
fn sweep_preserves_cycle_and_collects_unreachable() {
let mut vm = Vm::new();
let root = plain_object(&mut vm);
let child = plain_object(&mut vm);
let dead = plain_object(&mut vm);
unsafe {
(*root).set_prop_at(0, JsValue::from_js_object(child));
(*child).set_prop_at(0, JsValue::from_js_object(root));
}
let root_session = vm.promote_object(root);
vm.regs[0] = JsValue::from_js_object(root_session);
let dead_session = vm.promote_object(dead);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.mark(&vm);
let _ = gc.sweep(&mut vm);
vm.gc_state.session_gc = gc;
assert_eq!(vm.gc_state.session_object_ptrs.len(), 2);
assert!(!vm.gc_state.session_object_ptrs.contains(&root_session));
assert!(!vm.gc_state.session_object_ptrs.contains(&dead_session));
assert!(!vm
.gc_state
.session_object_ptrs
.iter()
.any(|ptr| unsafe { (*(*ptr)).is_gc_marked() }));
}
#[test]
fn forwarding_is_cleared_after_sweep() {
let mut vm = Vm::new();
let root = plain_object(&mut vm);
let child = plain_object(&mut vm);
unsafe {
(*root).set_prop_at(0, JsValue::from_js_object(child));
}
let root_session = vm.promote_object(root);
vm.regs[0] = JsValue::from_js_object(root_session);
let _ = vm.promote_object(child);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.mark(&vm);
let _ = gc.sweep(&mut vm);
vm.gc_state.session_gc = gc;
// The reused forwarding map MUST be cleared after sweep, otherwise
// promote would observe stale old->new entries pointing into the freed arena.
assert!(vm.gc_state.forwarding.is_empty());
}
fn vm_with_low_threshold() -> Vm {
let mut cfg = KernelConfig::minimal();
cfg.set_session_gc_threshold(1);
let core = KernelCore::new(cfg);
Vm::with_kernel_core(core)
}
fn native_ok(result: NativeResult) -> JsValue {
match result {
NativeResult::Ok(value) => value,
NativeResult::Err(err) => panic!("native error: {err}"),
NativeResult::TailCall { .. } => panic!("unexpected native bytecode call"),
}
}
#[test]
fn reset_maybe_collect_collects_after_threshold() {
let mut vm = vm_with_low_threshold();
let obj = plain_object(&mut vm);
vm.promote_object(obj);
assert!(!vm.gc_state.session_object_ptrs.is_empty());
let tracked_before = vm.gc_state.session_object_ptrs.len();
vm.regs[0] = JsValue::undefined();
vm.regs[1] = JsValue::undefined();
vm.reset();
assert!(vm.gc_state.session_object_ptrs.len() <= tracked_before);
assert_eq!(vm.gc_state.session_object_ptrs.len(), 0);
assert_eq!(vm.gc_state.session_bytes_allocated, 0);
}
#[test]
fn gc_stats_summary_includes_collection() {
let mut vm = vm_with_low_threshold();
let obj = plain_object(&mut vm);
vm.promote_object(obj);
vm.regs[0] = JsValue::undefined();
vm.maybe_collect_session_gc();
let summary = vm.gc_state.session_gc.stats_summary();
assert!(summary.contains("[GC] collection"));
}
#[test]
fn moving_sweep_rewrites_global_root_edges() {
let mut vm = vm_with_low_threshold();
let obj = plain_object(&mut vm);
unsafe {
(*obj).set_prop_at(0, JsValue::int(42));
}
let old_ptr = vm.promote_object(obj);
let key = vm.kernel_core.perm_interner().intern("gcRoot").0;
let global_ptr = vm.session.global_object().as_ptr() as *mut JsObject;
unsafe {
let global = &mut *global_ptr;
vm.set_or_create_prop_value(global, key, JsValue::from_js_object(old_ptr));
}
vm.maybe_collect_session_gc();
let global = vm.session.global_object();
let pos = vm
.kernel_core
.shape_forge()
.lookup_position(global.shape_id(), key)
.expect("global slot");
let new_value = global.get_prop_at(pos);
assert!(new_value.is_object());
assert!(!std::ptr::eq(new_value.as_js_object_ptr(), old_ptr));
assert_eq!(unsafe { (*new_value.as_js_object_ptr()).get_prop_at(0) }, JsValue::int(42));
}
#[test]
fn map_native_storage_is_not_a_normal_object_edge() {
let mut vm = Vm::new();
let map_value = native_ok(map::map_constructor(&mut vm, &[]));
let map_obj = unsafe { &*map_value.as_js_object_ptr() };
let native_ptr = map_obj.native_data() as *mut JsObject;
assert!(map_obj.hash_props_vec().is_none());
assert!(!map_obj.native_data().is_null());
assert!(!SessionGc::object_edges(map_obj)
.iter()
.any(|edge| std::ptr::eq(edge.as_js_object_ptr(), native_ptr)));
}
#[test]
fn session_gc_traces_map_object_key_and_value() {
let mut vm = vm_with_low_threshold();
let map_value = native_ok(map::map_constructor(&mut vm, &[]));
let key = JsValue::from_js_object(plain_object(&mut vm));
let value = JsValue::from_js_object(plain_object(&mut vm));
vm.regs[0] = map_value;
vm.regs[1] = key;
vm.regs[2] = value;
native_ok(map::map_set(&mut vm, &[0, 1, 2]));
let map_session = vm.promote_object(map_value.as_js_object_ptr());
vm.regs.fill(JsValue::undefined());
vm.regs[0] = JsValue::from_js_object(map_session);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.collect(&mut vm);
vm.gc_state.session_gc = gc;
let live_map = unsafe { &*vm.regs[0].as_js_object_ptr() };
let edges = map::map_native_edges(live_map);
assert_eq!(edges.len(), 2);
assert!(edges.iter().all(|value| vm.is_session_ptr(value.as_js_object_ptr())));
assert_eq!(vm.gc_state.session_object_ptrs.len(), 3);
}
#[test]
fn session_gc_traces_set_object_key() {
let mut vm = vm_with_low_threshold();
let set_value = native_ok(set::set_constructor(&mut vm, &[]));
let key = JsValue::from_js_object(plain_object(&mut vm));
vm.regs[0] = set_value;
vm.regs[1] = key;
native_ok(set::set_add(&mut vm, &[0, 1]));
let set_session = vm.promote_object(set_value.as_js_object_ptr());
vm.regs.fill(JsValue::undefined());
vm.regs[0] = JsValue::from_js_object(set_session);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.collect(&mut vm);
vm.gc_state.session_gc = gc;
let live_set = unsafe { &*vm.regs[0].as_js_object_ptr() };
let edges = set::set_native_edges(live_set);
assert_eq!(edges.len(), 1);
assert!(vm.is_session_ptr(edges[0].as_js_object_ptr()));
assert_eq!(vm.gc_state.session_object_ptrs.len(), 2);
}
#[test]
fn session_gc_keeps_shared_array_buffer_alive_through_view_native_edges() {
let mut vm = vm_with_low_threshold();
let root = plain_object(&mut vm);
vm.regs[1] = JsValue::int(8);
let buffer = native_ok(array_buffer::array_buffer_constructor(&mut vm, &[0, 1]));
vm.regs[1] = buffer;
let typed = native_ok(typed_array::int32array_constructor(&mut vm, &[0, 1]));
vm.regs[1] = buffer;
let view = native_ok(data_view::data_view_constructor(&mut vm, &[0, 1]));
vm.regs[0] = view;
vm.regs[1] = JsValue::int(0);
vm.regs[2] = JsValue::int(42);
vm.regs[3] = JsValue::bool(true);
native_ok(data_view::data_view_set_int32(&mut vm, &[0, 1, 2, 3]));
unsafe {
(*root).set_prop_at(0, typed);
(*root).set_prop_at(1, view);
}
let root_session = vm.promote_object(root);
vm.regs.fill(JsValue::undefined());
vm.regs[0] = JsValue::from_js_object(root_session);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.collect(&mut vm);
vm.gc_state.session_gc = gc;
let live_root = unsafe { &*vm.regs[0].as_js_object_ptr() };
let live_typed = live_root.get_prop_at(0);
let live_view = live_root.get_prop_at(1);
let typed_obj = unsafe { &*live_typed.as_js_object_ptr() };
let view_obj = unsafe { &*live_view.as_js_object_ptr() };
let typed_edges = typed_array::typed_array_native_edges(typed_obj);
let view_edges = data_view::data_view_native_edges(view_obj);
assert_eq!(typed_edges.len(), 1);
assert_eq!(view_edges.len(), 1);
assert!(vm.is_session_ptr(typed_edges[0].as_js_object_ptr()));
assert!(vm.is_session_ptr(view_edges[0].as_js_object_ptr()));
assert!(std::ptr::eq(typed_edges[0].as_js_object_ptr(), view_edges[0].as_js_object_ptr()));
vm.regs[0] = live_typed;
vm.regs[1] = JsValue::int(0);
assert_eq!(native_ok(typed_array::typed_array_at(&mut vm, &[0, 1])), JsValue::int(42));
vm.regs[0] = live_view;
vm.regs[1] = JsValue::int(4);
vm.regs[2] = JsValue::int(7);
vm.regs[3] = JsValue::bool(true);
native_ok(data_view::data_view_set_int32(&mut vm, &[0, 1, 2, 3]));
vm.regs[0] = live_typed;
vm.regs[1] = JsValue::int(1);
assert_eq!(native_ok(typed_array::typed_array_at(&mut vm, &[0, 1])), JsValue::int(7));
}
#[test]
fn session_gc_rewrites_buffer_retained_only_by_data_view_native_edge() {
let mut vm = vm_with_low_threshold();
vm.regs[1] = JsValue::int(8);
let buffer = native_ok(array_buffer::array_buffer_constructor(&mut vm, &[0, 1]));
vm.regs[1] = buffer;
let view = native_ok(data_view::data_view_constructor(&mut vm, &[0, 1]));
vm.regs[0] = view;
vm.regs[1] = JsValue::int(0);
vm.regs[2] = JsValue::int(9);
native_ok(data_view::data_view_set_int32(&mut vm, &[0, 1, 2]));
let view_session = vm.promote_object(view.as_js_object_ptr());
vm.regs.fill(JsValue::undefined());
vm.regs[0] = JsValue::from_js_object(view_session);
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.collect(&mut vm);
vm.gc_state.session_gc = gc;
let live_view = vm.regs[0];
let live_view_obj = unsafe { &*live_view.as_js_object_ptr() };
let edges = data_view::data_view_native_edges(live_view_obj);
assert_eq!(edges.len(), 1);
assert!(vm.is_session_ptr(edges[0].as_js_object_ptr()));
assert_eq!(vm.gc_state.session_object_ptrs.len(), 2);
vm.regs[0] = live_view;
vm.regs[1] = JsValue::int(0);
assert_eq!(native_ok(data_view::data_view_get_int32(&mut vm, &[0, 1])), JsValue::int(9));
}
fn collect(vm: &mut Vm) {
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
gc.collect(vm);
vm.gc_state.session_gc = gc;
}
#[test]
fn session_string_collected_when_dead() {
let mut vm = Vm::new();
let dead = vm.new_string("dead-string");
let dead_ptr = dead.as_string_ptr_mut();
assert!(vm.gc_state.session_string_ptrs.contains(&dead_ptr));
// No root references `dead` (it lives only on the Rust stack as a value wrapper).
collect(&mut vm);
assert!(!vm.gc_state.session_string_ptrs.contains(&dead_ptr));
}
#[test]
fn session_string_survives_when_in_register() {
let mut vm = Vm::new();
let live = vm.new_string("live-in-reg");
let live_ptr = live.as_string_ptr_mut();
vm.regs[0] = live;
collect(&mut vm);
assert!(vm.gc_state.session_string_ptrs.contains(&live_ptr));
// Live strings are never moved — the register still points at the same box.
assert_eq!(vm.regs[0].as_string_ptr_mut(), live_ptr);
assert_eq!(unsafe { (*live_ptr).as_str() }, "live-in-reg");
}
#[test]
fn session_string_survives_via_object_property() {
let mut vm = Vm::new();
let obj = plain_object(&mut vm);
let s = vm.new_string("prop-string");
let s_ptr = s.as_string_ptr_mut();
unsafe {
(*obj).set_prop_at(0, s);
}
let obj_session = vm.promote_object(obj);
// The string is reachable ONLY through the live object's property, not via any register.
vm.regs.fill(JsValue::undefined());
vm.regs[0] = JsValue::from_js_object(obj_session);
collect(&mut vm);
assert!(vm.gc_state.session_string_ptrs.contains(&s_ptr));
assert_eq!(unsafe { (*s_ptr).as_str() }, "prop-string");
}
#[test]
fn permanent_string_untouched_by_sweep() {
let mut vm = Vm::new();
let perm = vm.perm_string("perm");
let perm_ptr = perm.as_string_ptr_mut();
// Permanent strings live in PermInterner, never in the session set.
assert!(!vm.gc_state.session_string_ptrs.contains(&perm_ptr));
vm.regs[0] = perm;
collect(&mut vm);
// Never dropped by the session sweep (still readable, still absent from session set).
assert!(!vm.gc_state.session_string_ptrs.contains(&perm_ptr));
assert_eq!(unsafe { (*perm_ptr).as_str() }, "perm");
}
#[test]
fn string_sweep_byte_accounting() {
let mut vm = Vm::new();
let dead = vm.new_string("0123456789");
let _ = dead.as_string_ptr_mut();
let expected = (size_of::<JsString>() + "0123456789".len()) as u64;
let mut gc = std::mem::take(&mut vm.gc_state.session_gc);
let before = gc.total_bytes_freed;
gc.collect(&mut vm);
let after = gc.total_bytes_freed;
vm.gc_state.session_gc = gc;
assert!(after >= before + expected);
}
}