xo-alloc/xo-gc/src/gc/DX1Collector.cpp

836 lines
29 KiB
C++

/** @file DX1Collector.cpp
*
* @author Roland Conybeare, Dec 2025
**/
#include "Allocator.hpp"
#include "detail/IAllocator_DX1Collector.hpp"
#include "detail/ICollector_DX1Collector.hpp"
#include "arena/IAllocator_DArena.hpp"
#include "xo/gc/DX1Collector.hpp"
#include "xo/gc/DX1CollectorIterator.hpp"
#include "generation.hpp"
#include "object_age.hpp"
#include <xo/facet/obj.hpp>
#include <xo/indentlog/scope.hpp>
#include <cassert>
#include <cstdint>
#include <sys/mman.h>
#include <unistd.h> // for ::getpagesize()
namespace xo {
using xo::mm::AAllocator;
using xo::facet::typeseq;
using xo::facet::with_facet;
namespace mm {
X1CollectorConfig
X1CollectorConfig::with_name(std::string name)
{
X1CollectorConfig copy = *this;
copy.name_ = std::move(name);
return copy;
}
X1CollectorConfig
X1CollectorConfig::with_size(std::size_t gen_z)
{
X1CollectorConfig copy = *this;
copy.arena_config_ = arena_config_.with_size(gen_z);
return copy;
}
// ----- GCRunState -----
GCRunState::GCRunState(generation gc_upto)
: gc_upto_{gc_upto}
{}
GCRunState
GCRunState::gc_not_running()
{
return GCRunState(generation(0));
}
GCRunState
GCRunState::gc_upto(generation g)
{
return GCRunState(generation(g + 1));
}
// ----- DX1Collector -----
using size_type = xo::mm::DX1Collector::size_type;
DX1Collector::DX1Collector(const X1CollectorConfig & cfg) : config_{cfg}
{
assert(config_.arena_config_.header_.size_bits_ +
config_.arena_config_.header_.age_bits_ +
config_.arena_config_.header_.tseq_bits_ <= 64);
size_t page_z = getpagesize();
/* 1MB reserved address space enough for up to 128k distinct types.
* In this case don't want to use hugepages since actual #of types
* likely << .size/8
*/
object_types_ = DArena::map(
ArenaConfig{
.name_ = "x1-object-types",
.size_ = cfg.object_types_z_,
.hugepage_z_ = page_z,
.store_header_flag_ = false});
roots_ = DArena::map(
ArenaConfig{
.name_ = "x1-object-roots",
.size_ = cfg.object_roots_z_,
.hugepage_z_ = page_z,
.store_header_flag_ = false});
for (uint32_t igen = 0, ngen = cfg.n_generation_; igen < ngen; ++igen) {
{
char buf[40];
snprintf(buf, sizeof(buf), "x1-space-G%u-a", igen);
space_storage_[0][igen] = DArena::map(cfg.arena_config_.with_name(std::string(buf)));
}
{
char buf[40];
snprintf(buf, sizeof(buf), "x1-space-G%u-b", igen);
space_storage_[1][igen] = DArena::map(cfg.arena_config_.with_name(std::string(buf)));
}
space_[role::to_space()][igen] = &space_storage_[0][igen];
space_[role::from_space()][igen] = &space_storage_[1][igen];
}
for (uint32_t igen = cfg.n_generation_; igen < c_max_generation; ++igen) {
space_[role::to_space()][igen] = nullptr;
space_[role::from_space()][igen] = nullptr;
}
}
void
DX1Collector::visit_pools(const MemorySizeVisitor & visitor) const
{
object_types_.visit_pools(visitor);
roots_.visit_pools(visitor);
for (uint32_t i = 0; i < c_n_role; ++i) {
for (uint32_t j = 0; j < config_.n_generation_; ++j) {
space_storage_[i][j].visit_pools(visitor);
}
}
}
bool
DX1Collector::contains(role r, const void * addr) const noexcept
{
for (generation gi{0}; gi < config_.n_generation_; ++gi) {
const DArena * arena = get_space(r, gi);
if (arena->contains(addr))
return true;
}
return false;
}
AllocError
DX1Collector::last_error() const noexcept
{
// TODO:
// need to adjust here if runtime errors
// encountered during gc.
return get_space(role::to_space(), generation::nursery())->last_error_;
}
namespace {
size_type
accumulate_total_aux(const DX1Collector & d,
size_t (DArena::* get_stat_fn)() const) noexcept
{
size_t z1 = (d.object_types_.*get_stat_fn)();
size_t z2 = (d.roots_.*get_stat_fn)();
size_t z3 = 0;
for (role ri : role::all()) {
for (generation gj{0}; gj < d.config_.n_generation_; ++gj) {
const DArena * arena = d.get_space(ri, gj);
assert(arena);
z3 += (arena->*get_stat_fn)();
}
}
return z1 + z2 + z3;
}
}
size_type
DX1Collector::reserved_total() const noexcept
{
return accumulate_total_aux(*this, &DArena::reserved);
}
size_type
DX1Collector::size_total() const noexcept
{
return committed_total();
}
size_type
DX1Collector::committed_total() const noexcept
{
return accumulate_total_aux(*this, &DArena::committed);
}
size_type
DX1Collector::available_total() const noexcept
{
return accumulate_total_aux(*this, &DArena::available);
}
size_type
DX1Collector::allocated_total() const noexcept
{
return accumulate_total_aux(*this, &DArena::allocated);
}
size_type
DX1Collector::header2size(header_type hdr) const noexcept
{
uint32_t z = config_.arena_config_.header_.size(hdr);
return z;
}
object_age
DX1Collector::header2age(header_type hdr) const noexcept
{
uint32_t age = config_.arena_config_.header_.age(hdr);
assert(age < c_max_object_age);
return object_age(age);
}
uint32_t
DX1Collector::header2tseq(header_type hdr) const noexcept
{
uint32_t tseq = config_.arena_config_.header_.tseq(hdr);
return tseq;
}
bool
DX1Collector::is_forwarding_header(header_type hdr) const noexcept
{
/** forwarding pointer encoded as sentinel tseq **/
return config_.arena_config_.header_.is_forwarding_tseq(hdr);
}
bool
DX1Collector::is_type_installed(typeseq tseq) const noexcept
{
if (object_types_.committed() < sizeof(AGCObject) * (tseq.seqno() + 1))
return false;
AGCObject * v = reinterpret_cast<AGCObject *>(object_types_.lo_);
void * vtable = *(void **)&(v[tseq.seqno()]);
return (vtable != nullptr);
}
const AGCObject *
DX1Collector::lookup_type(typeseq tseq) const noexcept
{
AGCObject * v = reinterpret_cast<AGCObject *>(object_types_.lo_);
return &(v[tseq.seqno()]);
}
/* editor bait: register_type */
bool
DX1Collector::install_type(const AGCObject & meta) noexcept
{
typeseq tseq = meta._typeseq();
bool ok = object_types_.expand(sizeof(AGCObject) * (tseq.seqno() + 1));
if (!ok)
return false;
AGCObject * v = reinterpret_cast<AGCObject *>(object_types_.lo_);
/* explicitly copying vtable pointer here */
std::memcpy((void*)&(v[tseq.seqno()]), (void*)&meta, sizeof(AGCObject));
return true;
}
void
DX1Collector::add_gc_root_poly(obj<AGCObject> * p_root) noexcept
{
std::byte * mem
= roots_.alloc(typeseq::anon(),
sizeof(obj<AGCObject>*));
assert(mem);
*(obj<AGCObject> **)mem = p_root;
}
void
DX1Collector::request_gc(generation upto) noexcept
{
if (gc_blocked_ > 0) {
if (gc_pending_upto_ < upto) {
this->gc_pending_upto_ = upto;
}
/* intend collecting later */
} else {
this->execute_gc(upto);
}
}
void
DX1Collector::execute_gc(generation upto) noexcept
{
scope log(XO_DEBUG(true), xtag("upto", upto));
assert(!runstate_.is_running());
//auto t0 = std::chrono::steady_clock::now();
log && log("step 0a : update run state");
this->runstate_ = GCRunState::gc_upto(upto);
log && log("step 0a : [STUB] snapshot alloc state");
log && log("step 0b : [STUB] scan for object statistics");
log && log("step 1 : swap from/to roles");
this->swap_roles(upto);
log && log(xtag("from_0", get_space(role::from_space(), generation{0})->lo_),
xtag("to_0", get_space(role::to_space(), generation{0})->lo_));
log && log("step 2a : copy roots");
this->copy_roots(upto);
log && log("step 2b : [STUB] copy pinned");
log && log("step 3a : [STUB] run destructors");
log && log("step 3b : [STUB] keep reachable weak pointers");
log && log("step 4 : [STUB] cleanup");
}
void
DX1Collector::swap_roles(generation upto) noexcept
{
scope log(XO_DEBUG(true), xtag("upto", upto));
for (generation g = generation{0}; g < upto; ++g) {
log && log("swap roles", xtag("g", g));
std::swap(space_[role::to_space()][g], space_[role::from_space()][g]);
}
}
/*
* rules:
* - from_src must be in from-space
* - object type stored in alloc header
* - return value is new location in to-space
*
* - preserving i/face pointer
* - replace destination with forwarding pointer
*
* EDITOR: gc -> self
*/
void *
DX1Collector::deep_move(void * from_src, generation upto)
{
scope log(XO_DEBUG(config_.debug_flag_));
if (!from_src)
return nullptr;
if (!this->contains(role::from_space(), from_src)) {
/* presumeably memory not owned by collector
* (e.g. DBoolean {true, false}, DUniqueString {owned by StringTable} etc.)
*/
return from_src;
}
AllocInfo info = this->alloc_info((std::byte *)from_src);
AllocHeader hdr = info.header();
typeseq tseq(info.tseq());
if (is_forwarding_header(hdr)) {
/* already forwarded - pickup destination
*
* Coordinates with forward_inplace()
*/
log && log("disposition: already forwarded");
return *(void **)from_src;
}
/* here: object at from_src not already forwarded */
if (!this->check_move_policy(hdr, from_src)) {
/* object at from_src in generation that is not being collected */
log && log("disposition: not moving from_src");
return from_src;
}
/**
* To-space:
*
* to_lo = start of to-space
* w,W = white objects. An object x is white if x
* + all immediate children of x are in to-space
* (also implies this GC cycle put it there)
* g,G = grey objects. An object x is gray if it's in to-space,
* but possibly has >0 black children
* _ = free to-space memory
* N = nursery space (generation{0})
* T = tenured space (generation{1})
*
* wwwwwwwwwwwwwwwwwwwggggggggggggggggggggg_________________...
* ^ ^ ^
* to_lo grey_lo(N) free_ptr(N)
*
* After moving children of one object,
* advancing {nursery_grey_lo, nursery_free_ptr}
*
* wwwwwwwwwwwwwwwwwwwWWWWgggggggggggggggggGGGGGGGGGGG______...
* ^ ^ ^
* to_lo grey_lo(N) free_ptr(N)
*
* Invariant:
*
* objects in [to_lo, gray_lo) are white.
* all gray objects are in [gray_lo, free_ptr)
* memory starting at free_ptr is free.
*
* deep_move terminates when gray_lo catches up to free_ptr
*
* Above is simplified. Complication is that GC (including incremental) may
* promote objects from nursery (N) to tenured (T)
*
* So more accurate before/after picture
*
* N wwwwwwwwwwwwwwwwwwwggggggggggggggggggggg_________________...
* ^ ^ ^
* to_lo(N) grey_lo(N) free_ptr(N)
*
* T wwwwwwwwwwwwwwgggggggggggg_______________________________...
* ^ ^ ^
* to_lo(T) grey_lo(T) free_ptr(N)
*
* After moving children of one object,
* advancing {nursery_grey_lo, nursery_free_ptr}
*
* N wwwwwwwwwwwwwwwwwwwWWWWgggggggggggggggggGGGGGGGGGGG_____...
* ^ ^ ^
* to_lo(N) grey_lo(N) free_ptr(N)
*
* T wwwwwwwwwwwwwwggggggggggggGGGGG_________________________...
* ^ ^ ^
* to_lo(T) grey_lo(T) free_ptr(T)
*
* deep_move terminates when both:
* - gray_lo(N) catches up with free_ptr(N)
* - gray_lo(T) catches up with free_ptr(T)
*
**/
log && log("disposition: move subtree");
/* TODO: AllocIterator pointing to free pointer */
std::array<std::byte *, c_max_generation> gray_lo_v;
{
for (uint32_t g = 0; g < upto; ++g) {
gray_lo_v[g] = this->to_space(generation{g})->free_;
}
}
obj<AAllocator, DX1Collector> alloc(this);
const AGCObject * iface = lookup_type(tseq);
void * to_dest = this->shallow_move(iface, from_src);
std::size_t fixup_work = 0;
/* TODO:
* - loop here is bad for memory locality
* - replace with depth-first traversal
*/
do {
fixup_work = 0;
for (generation g = generation{0}; g < upto; ++g) {
/* TODO: use AllocIterator here */
while(gray_lo_v[g] < to_space(g)->free_) {
AllocHeader * hdr = (AllocHeader *)gray_lo_v[g];
void * src = (hdr + 1);
log && log("fwd children", xtag("src", src));
const auto & hdr_cfg = config_.arena_config_.header_;
typeseq tseq = typeseq(hdr_cfg.tseq(*hdr));
size_t z = hdr_cfg.size_with_padding(*hdr);
const AGCObject * iface = this->lookup_type(tseq);
obj<ACollector, DX1Collector> gc(this);
iface->forward_children(src, gc);
gray_lo_v[g] = ((std::byte *)src) + z;
++fixup_work;
}
}
} while (fixup_work > 0);
log && log(xtag("to_dest", to_dest));
return to_dest;
}
void
DX1Collector::copy_roots(generation upto) noexcept
{
scope log(XO_DEBUG(true));
for (obj<AGCObject> ** p_root = (obj<AGCObject> **)roots_.lo_;
p_root < (obj<AGCObject> **)roots_.free_; ++p_root)
{
log && log("copy root", xtag("**p_root.data.pre", (**p_root).data_));
(*p_root)->reset_opaque(this->deep_move((*p_root)->data_, upto));
log && log(xtag("**p_root.data.post", (**p_root).data_));
}
}
void
DX1Collector::forward_inplace(AGCObject * lhs_iface,
void ** lhs_data)
{
scope log(XO_DEBUG(config_.debug_flag_),
xtag("lhs_data", lhs_data),
xtag("*lhs_data", *lhs_data));
/* coordinates with DX1Collector::_deep_move() */
(void)lhs_iface;
assert(runstate_.is_running());
/*
* lhs obj<AGCObject>
* | +---------+ +---+-+----+
* \--->| .iface | | T |G|size| header
* +---------+ object_data +---+-+----+
* | .data x----------------->| alloc |
* +---------+ | data |
* | for |
* | instance |
* | ... |
* +----------+
*/
void * object_data = (std::byte *)*lhs_data;
if (!this->contains(role::from_space(), object_data)) {
/* *lhs_data either:
* 1. already in to-space
* 2. not in GC-allocated space at all
* (small number of niche examples of this)
*
* It's important we recognize case (2) up front.
* Since not allocated from GC, they don't have
* an alloc-header.
*/
log && log("disposition: not in from-space");
return;
}
log && log("disposition: in from-space");
/** NOTE: for form's sake:
* lookup actual arena that
* allocated object data.
* Only using this to get alloc header
**/
DArena * some_arena = this->from_space(generation(0));
DArena::header_type * p_header
= some_arena->obj2hdr(object_data);
DArena::header_type alloc_hdr = *p_header;
/* recover allocation size */
std::size_t alloc_z = some_arena->config_.header_.size_with_padding(alloc_hdr);
log && log(xtag("some_arena.lo", some_arena->lo_),
xtag("p_header", p_header),
xtag("alloc_z", alloc_z));
/* need to be able to fit forwarding pointer
* in place of forwarded object.
*
* This is guaranteed anyway, by alignment rules
*/
assert(alloc_z >= sizeof(uintptr_t));
if (this->is_forwarding_header(alloc_hdr)) {
/* *lhs_data already refers to a forwarding pointer */
/*
* lhs obj<AGCObject> (from-space)
* | +---------+ +---+-+----+
* \--->| .iface | |FWD|G|size| alloc_hdr
* +---------+ object_data +---+-+----+
* | .data x----------------->| x--------\
* +---------+ | | | dest
* | | |
* +----------+ |
* |
* (to-space) |
* +---+-+----+ |
* |FWD|G|size|<--/
* +---+-+----+
* | |
* | |
* | |
* +----------+
*/
void * dest = *(void**)object_data;
*lhs_data = dest;
/*
* lhs obj<AGCObject>
* | +---------+
* \--->| .iface |
* +---------+
* | .data x------------\
* +---------+ |
* | dest
* |
* |
* | (to-space)
* | +---+-+----+
* \---->|FWD|G|size|
* +---+-+----+
* | |
* | |
* | |
* +----------+
*/
} else if (this->check_move_policy(alloc_hdr, object_data)) {
/* copy object *lhs + replace with forwarding pointer */
/*
* lhs obj<AGCObject> (from-space)
* | +---------+ +---+-+----+
* \--->| .iface | |FWD|G|size| alloc_hdr
* +---------+ object_data +---+-+----+
* | .data x----------------->| |
* +---------+ | |
* | |
* +----------+
*/
*lhs_data = this->shallow_move(lhs_iface, *lhs_data);
/*
* lhs obj<AGCObject> (from-space)
* | +---------+ +---+-+----+
* \--->| .iface | |FWD|G|SIZE|
* +---------+ +---+-+----+
* | .data x------------\ | x--------\
* +---------+ | | | |
* | | | |
* dest | +----------+ |
* | |
* | (to-space) |
* | +---+-+----+ |
* \---->|FWD|G|size|<--/
* +---+-+----+
* | |
* | |
* | |
* +----------+
*/
} else {
/* object doesn't need to move.
* e.g. incremental collection + object is tenured
*/
}
} /*forward_inplace*/
void *
DX1Collector::shallow_move(const AGCObject * iface, void * from_src)
{
scope log(XO_DEBUG(config_.debug_flag_));
AllocInfo info = this->alloc_info((std::byte *)from_src);
obj<AAllocator, DX1Collector> alloc(this);
void * to_dest = iface->shallow_copy(from_src, alloc);
log && log(xtag("from_src", from_src), xtag("to_dest", to_dest));
if(to_dest == from_src) {
assert(false);
} else {
*(const_cast<AllocHeader*>(info.p_header_))
= AllocHeader(config_
.arena_config_
.header_
.mark_forwarding_tseq(*info.p_header_));
*(void **)from_src = to_dest;
}
return to_dest;
}
bool
DX1Collector::check_move_policy(header_type alloc_hdr,
void * object_data) const noexcept
{
(void)object_data;
// when gc is moving objects, to- and from- spaces have been
// reversed: forwarding pointers are located in from-space and
// refer to to-space.
object_age age = this->header2age(alloc_hdr);
generation g = config_.age2gen(age);
assert(runstate_.is_running());
return (g < runstate_.gc_upto());
}
auto
DX1Collector::alloc(typeseq t, size_type z) noexcept -> value_type
{
return with_facet<AAllocator>::mkobj(new_space()).alloc(t, z);
}
auto
DX1Collector::super_alloc(typeseq t, size_type z) noexcept -> value_type {
return with_facet<AAllocator>::mkobj(new_space()).super_alloc(t, z);
}
auto
DX1Collector::sub_alloc(size_type z, bool complete) noexcept -> value_type {
return with_facet<AAllocator>::mkobj(new_space()).sub_alloc(z, complete);
}
auto
DX1Collector::alloc_copy(value_type src) noexcept -> value_type {
return with_facet<AAllocator>::mkobj(new_space()).alloc_copy(src);
}
bool
DX1Collector::expand(size_type z) noexcept
{
if (with_facet<AAllocator>::mkobj(to_space(generation{0})).expand(z))
return with_facet<AAllocator>::mkobj(from_space(generation{0})).expand(z);
return false;
}
AllocInfo
DX1Collector::alloc_info(value_type mem) const noexcept {
for (role ri : role::all()) {
for (generation gj{0}; gj < config_.n_generation_; ++gj) {
const DArena * arena = this->get_space(ri, gj);
assert(arena);
if (arena->contains(mem)) {
return arena->alloc_info(mem);
}
}
}
// deliberately attempt on nursery to-space, to capture error info + return sentinel
return this->get_space(role::to_space(), generation{0})->alloc_info(mem);
}
DX1CollectorIterator
DX1Collector::begin() const noexcept
{
scope log(XO_DEBUG(false));
const DArena * arena
= get_space(role::to_space(),
generation{0});
return DX1CollectorIterator(this,
generation{0},
generation{config_.n_generation_},
arena->begin(),
arena->end());
}
DX1CollectorIterator
DX1Collector::end() const noexcept {
scope log(XO_DEBUG(false));
generation gen_hi = generation{config_.n_generation_};
/** valid iterator for end points to end of last DArena.
* otherwise will interfere with working compare
* (since invalid iterators are incomparable)
**/
const DArena * arena
= get_space(role::to_space(),
generation(config_.n_generation_ - 1));
DArenaIterator arena_end = arena->end();
return DX1CollectorIterator(this,
gen_hi,
gen_hi,
arena_end,
arena_end);
}
void
DX1Collector::reverse_roles(generation g) noexcept {
assert(g < config_.n_generation_);
std::swap(space_[role::from_space()][g], space_[role::to_space()][g]);
}
void
DX1Collector::clear() noexcept {
for (role ri : role::all()) {
for (generation gj{0}; gj < config_.n_generation_; ++gj) {
DArena * arena = this->get_space(ri, gj);
assert(arena);
arena->clear();
}
}
}
} /*namespace mm*/
} /*namespace xo*/
/* end DX1Collector.cpp */