global.rs

use super::gc_work::GenCopyGCWorkContext;
use super::gc_work::GenCopyNurseryGCWorkContext;
use super::mutator::ALLOCATOR_MAPPING;
use crate::plan::generational::global::Gen;
use crate::plan::global::BasePlan;
use crate::plan::global::CommonPlan;
use crate::plan::global::CreateGeneralPlanArgs;
use crate::plan::global::CreateSpecificPlanArgs;
use crate::plan::global::GcStatus;
use crate::plan::AllocationSemantics;
use crate::plan::Plan;
use crate::plan::PlanConstraints;
use crate::policy::copyspace::CopySpace;
use crate::policy::space::Space;
use crate::scheduler::*;
use crate::util::alloc::allocators::AllocatorSelector;
use crate::util::copy::*;
use crate::util::heap::VMRequest;
use crate::util::metadata::side_metadata::SideMetadataSanity;
use crate::util::VMWorkerThread;
use crate::vm::*;
use enum_map::EnumMap;
use std::sync::atomic::{AtomicBool, Ordering};

use mmtk_macros::PlanTraceObject;

#[derive(PlanTraceObject)]
pub struct GenCopy<VM: VMBinding> {
    #[fallback_trace]
    pub gen: Gen<VM>,
    pub hi: AtomicBool,
    #[trace(CopySemantics::Mature)]
    pub copyspace0: CopySpace<VM>,
    #[trace(CopySemantics::Mature)]
    pub copyspace1: CopySpace<VM>,
}

pub const GENCOPY_CONSTRAINTS: PlanConstraints = crate::plan::generational::GEN_CONSTRAINTS;

impl<VM: VMBinding> Plan for GenCopy<VM> {
    type VM = VM;

    fn constraints(&self) -> &'static PlanConstraints {
        &GENCOPY_CONSTRAINTS
    }

    fn create_copy_config(&'static self) -> CopyConfig<Self::VM> {
        use enum_map::enum_map;
        CopyConfig {
            copy_mapping: enum_map! {
                CopySemantics::Mature => CopySelector::CopySpace(0),
                CopySemantics::PromoteToMature => CopySelector::CopySpace(0),
                _ => CopySelector::Unused,
            },
            space_mapping: vec![
                // The tospace argument doesn't matter, we will rebind before a GC anyway.
                (CopySelector::CopySpace(0), self.tospace()),
            ],
            constraints: &GENCOPY_CONSTRAINTS,
        }
    }

    fn collection_required(&self, space_full: bool, space: Option<&dyn Space<Self::VM>>) -> bool
    where
        Self: Sized,
    {
        self.gen.collection_required(self, space_full, space)
    }

    fn force_full_heap_collection(&self) {
        self.gen.force_full_heap_collection()
    }

    fn last_collection_full_heap(&self) -> bool {
        self.gen.last_collection_full_heap()
    }

    fn get_spaces(&self) -> Vec<&dyn Space<Self::VM>> {
        let mut ret = self.gen.get_spaces();
        ret.push(&self.copyspace0);
        ret.push(&self.copyspace1);
        ret
    }

    fn schedule_collection(&'static self, scheduler: &GCWorkScheduler<VM>) {
        let is_full_heap = self.requires_full_heap_collection();
        self.base().set_collection_kind::<Self>(self);
        self.base().set_gc_status(GcStatus::GcPrepare);
        if is_full_heap {
            scheduler.schedule_common_work::<GenCopyGCWorkContext<VM>>(self);
        } else {
            scheduler.schedule_common_work::<GenCopyNurseryGCWorkContext<VM>>(self);
        }
    }

    fn get_allocator_mapping(&self) -> &'static EnumMap<AllocationSemantics, AllocatorSelector> {
        &*ALLOCATOR_MAPPING
    }

    fn prepare(&mut self, tls: VMWorkerThread) {
        let full_heap = !self.is_current_gc_nursery();
        self.gen.prepare(tls);
        if full_heap {
            self.hi
                .store(!self.hi.load(Ordering::SeqCst), Ordering::SeqCst); // flip the semi-spaces
        }
        let hi = self.hi.load(Ordering::SeqCst);
        self.copyspace0.prepare(hi);
        self.copyspace1.prepare(!hi);

        self.fromspace_mut()
            .set_copy_for_sft_trace(Some(CopySemantics::Mature));
        self.tospace_mut().set_copy_for_sft_trace(None);
    }

    fn prepare_worker(&self, worker: &mut GCWorker<Self::VM>) {
        unsafe { worker.get_copy_context_mut().copy[0].assume_init_mut() }.rebind(self.tospace());
    }

    fn release(&mut self, tls: VMWorkerThread) {
        let full_heap = !self.is_current_gc_nursery();
        self.gen.release(tls);
        if full_heap {
            self.fromspace().release();
        }

        // TODO: Refactor so that we set the next_gc_full_heap in gen.release(). Currently have to fight with Rust borrow checker
        // NOTE: We have to take care that the `Gen::should_next_gc_be_full_heap()` function is
        // called _after_ all spaces have been released (including ones in `gen`) as otherwise we
        // may get incorrect results since the function uses values such as available pages that
        // will change dependant on which spaces have been released
        self.gen
            .set_next_gc_full_heap(Gen::should_next_gc_be_full_heap(self));
    }

    fn get_collection_reserved_pages(&self) -> usize {
        self.gen.get_collection_reserved_pages() + self.tospace().reserved_pages()
    }

    fn get_used_pages(&self) -> usize {
        self.gen.get_used_pages() + self.tospace().reserved_pages()
    }

    /// Return the number of pages available for allocation. Assuming all future allocations goes to nursery.
    fn get_available_pages(&self) -> usize {
        // super.get_available_pages() / 2 to reserve pages for copying
        (self
            .get_total_pages()
            .saturating_sub(self.get_reserved_pages()))
            >> 1
    }

    fn get_mature_physical_pages_available(&self) -> usize {
        self.tospace().available_physical_pages()
    }

    fn base(&self) -> &BasePlan<VM> {
        &self.gen.common.base
    }

    fn common(&self) -> &CommonPlan<VM> {
        &self.gen.common
    }

    fn generational(&self) -> &Gen<VM> {
        &self.gen
    }

    fn is_current_gc_nursery(&self) -> bool {
        !self.gen.gc_full_heap.load(Ordering::SeqCst)
    }
}

impl<VM: VMBinding> GenCopy<VM> {
    pub fn new(args: CreateGeneralPlanArgs<VM>) -> Self {
        let mut plan_args = CreateSpecificPlanArgs {
            global_args: args,
            constraints: &GENCOPY_CONSTRAINTS,
            global_side_metadata_specs:
                crate::plan::generational::new_generational_global_metadata_specs::<VM>(),
        };

        let copyspace0 = CopySpace::new(
            plan_args.get_space_args("copyspace0", true, VMRequest::discontiguous()),
            false,
        );
        let copyspace1 = CopySpace::new(
            plan_args.get_space_args("copyspace1", true, VMRequest::discontiguous()),
            true,
        );

        let res = GenCopy {
            gen: Gen::new(plan_args),
            hi: AtomicBool::new(false),
            copyspace0,
            copyspace1,
        };

        // Use SideMetadataSanity to check if each spec is valid. This is also needed for check
        // side metadata in extreme_assertions.
        {
            let mut side_metadata_sanity_checker = SideMetadataSanity::new();
            res.gen
                .verify_side_metadata_sanity(&mut side_metadata_sanity_checker);
            res.copyspace0
                .verify_side_metadata_sanity(&mut side_metadata_sanity_checker);
            res.copyspace1
                .verify_side_metadata_sanity(&mut side_metadata_sanity_checker);
        }

        res
    }

    fn requires_full_heap_collection(&self) -> bool {
        self.gen.requires_full_heap_collection(self)
    }

    pub fn tospace(&self) -> &CopySpace<VM> {
        if self.hi.load(Ordering::SeqCst) {
            &self.copyspace1
        } else {
            &self.copyspace0
        }
    }

    pub fn tospace_mut(&mut self) -> &mut CopySpace<VM> {
        if self.hi.load(Ordering::SeqCst) {
            &mut self.copyspace1
        } else {
            &mut self.copyspace0
        }
    }

    pub fn fromspace(&self) -> &CopySpace<VM> {
        if self.hi.load(Ordering::SeqCst) {
            &self.copyspace0
        } else {
            &self.copyspace1
        }
    }

    pub fn fromspace_mut(&mut self) -> &mut CopySpace<VM> {
        if self.hi.load(Ordering::SeqCst) {
            &mut self.copyspace0
        } else {
            &mut self.copyspace1
        }
    }
}