Code cleanup

This commit is contained in:
Victor Olin 2023-03-08 16:47:34 +01:00
parent 7bb64c0489
commit cdc802476d
6 changed files with 503 additions and 459 deletions

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@ -6,8 +6,6 @@
#include "event.hpp"
#include "heap.hpp"
// using namespace std;
namespace GC {
GCEventType GCEvent::getType() {

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@ -8,405 +8,444 @@
#include <vector>
#include "../include/heap.hpp"
using namespace std;
namespace GC {
using std::cout, std::endl, std::vector, std::hex, std::dec;
/**
* Initialises the heap singleton and saves the address
* of the calling stack frame as the stack_top. Presumeably
* this address points to the stack frame of the compiled
* LLVM executable after linking.
*/
void Heap::init() {
Heap *heap = Heap::the();
heap->m_stack_top = reinterpret_cast<uintptr_t *>(__builtin_frame_address(1));
}
namespace GC
{
/**
* Disposes the heap at program exit.
*/
void Heap::dispose() {
Heap *heap = Heap::the();
delete heap;
}
/**
* Initialises the heap singleton and saves the address
* of the calling stack frame as the stack_top. Presumeably
* this address points to the stack frame of the compiled
* LLVM executable after linking.
*/
void Heap::init()
{
Heap *heap = Heap::the();
heap->m_stack_top = static_cast<uintptr_t *>(__builtin_frame_address(1));
}
/**
* Allocates a given amount of bytes on the heap.
*
* @param size The amount of bytes to be allocated.
*
* @return A pointer to the address where the memory
* has been allocated. This pointer is supposed
* to be casted to and object pointer.
*/
void *Heap::alloc(size_t size) {
/**
* Disposes the heap at program exit.
*/
void Heap::dispose()
{
Heap *heap = Heap::the();
delete heap;
}
// Singleton
Heap *heap = Heap::the();
if (size < 0) {
cout << "Heap: Cannot alloc less than 0B. No bytes allocated." << endl;
return nullptr;
}
/**
* Allocates a given amount of bytes on the heap.
*
* @param size The amount of bytes to be allocated.
*
* @return A pointer to the address where the memory
* has been allocated. This pointer is supposed
* to be casted to and object pointer.
*/
void *Heap::alloc(size_t size)
{
if (heap->m_size + size > HEAP_SIZE) {
heap->collect();
// If collect failed, crash with OOM error
assert(heap->m_size + size <= HEAP_SIZE && "Heap: Out Of Memory");
}
// Singleton
Heap *heap = Heap::the();
// If a chunk was recycled, return the old chunk address
uintptr_t *reused_chunk = heap->try_recycle_chunks(size);
if (reused_chunk != nullptr) {
return (void *)reused_chunk;
}
// If no free chunks was found (reused_chunk is a nullptr),
// then create a new chunk
auto new_chunk = new Chunk;
new_chunk->size = size;
new_chunk->start = (uintptr_t *)(heap->m_heap + heap->m_size);
if (size < 0)
{
cout << "Heap: Cannot alloc less than 0B. No bytes allocated." << endl;
return nullptr;
}
heap->m_size += size;
if (heap->m_size + size > HEAP_SIZE)
{
heap->collect();
// If collect failed, crash with OOM error
assert(heap->m_size + size <= HEAP_SIZE && "Heap: Out Of Memory");
}
heap->m_allocated_chunks.push_back(new_chunk);
// If a chunk was recycled, return the old chunk address
uintptr_t *reused_chunk = heap->try_recycle_chunks(size);
if (reused_chunk != nullptr)
{
return static_cast<void *>(reused_chunk);
}
// new_chunk should probably be a unique pointer, if that isn't implicit already
return new_chunk->start;
}
// If no free chunks was found (reused_chunk is a nullptr),
// then create a new chunk
auto new_chunk = new Chunk;
new_chunk->size = size;
new_chunk->start = (uintptr_t *)(heap->m_heap + heap->m_size);
/**
* Tries to recycle used and freed chunks that are
* already allocated objects by the OS but freed
* from our Heap. This reduces the amount of GC
* objects slightly which saves time from malloc'ing
* memory from the OS.
*
* @param size Amount of bytes needed for the object
* which is about to be allocated.
*
* @returns If a chunk is found and recycled, a
* pointer to the allocated memory for
* the object is returned. If not, a
* nullptr is returned to signify no
* chunks were found.
*/
uintptr_t *Heap::try_recycle_chunks(size_t size) {
auto heap = Heap::the();
// Check if there are any freed chunks large enough for current request
for (size_t i = 0; i < heap->m_freed_chunks.size(); i++) {
// auto cp = heap->m_freed_chunks.at(i);
auto cp = getAt(heap->m_freed_chunks, i);
auto iter = heap->m_freed_chunks.begin();
advance(iter, i);
if (cp->size > size)
{
// Split the chunk, use one part and add the remaining part to
// the list of freed chunks
size_t diff = cp->size - size;
auto chunk_complement = new Chunk;
chunk_complement->size = diff;
chunk_complement->start = cp->start + cp->size;
heap->m_size += size;
heap->m_freed_chunks.erase(iter);
heap->m_freed_chunks.push_back(chunk_complement);
heap->m_allocated_chunks.push_back(cp);
return cp->start;
}
else if (cp->size == size)
{
// Reuse the whole chunk
heap->m_freed_chunks.erase(iter);
heap->m_allocated_chunks.push_back(cp);
return cp->start;
}
}
return nullptr;
}
heap->m_allocated_chunks.push_back(new_chunk);
/**
* Collection phase of the garbage collector. When
* an allocation is requested and there is no space
* left on the heap, a collection is triggered. This
* function is private so that the user cannot trigger
* a collection unneccessarily.
*/
void Heap::collect() {
// Get instance
auto heap = Heap::the();
// new_chunk should probably be a unique pointer, if that isn't implicit already
return new_chunk->start;
}
// get current stack
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
/**
* Tries to recycle used and freed chunks that are
* already allocated objects by the OS but freed
* from our Heap. This reduces the amount of GC
* objects slightly which saves time from malloc'ing
* memory from the OS.
*
* @param size Amount of bytes needed for the object
* which is about to be allocated.
*
* @returns If a chunk is found and recycled, a
* pointer to the allocated memory for
* the object is returned. If not, a
* nullptr is returned to signify no
* chunks were found.
*/
uintptr_t *Heap::try_recycle_chunks(size_t size)
{
auto heap = Heap::the();
// Check if there are any freed chunks large enough for current request
for (size_t i = 0; i < heap->m_freed_chunks.size(); i++)
{
auto chunk = getAt(heap->m_freed_chunks, i);
auto iter = heap->m_freed_chunks.begin();
advance(iter, i);
if (chunk->size > size)
{
// Split the chunk, use one part and add the remaining part to
// the list of freed chunks
size_t diff = chunk->size - size;
uintptr_t *stack_top = heap->m_stack_top != nullptr ? heap->m_stack_top : (uintptr_t *)0;
auto chunk_complement = new Chunk;
chunk_complement->size = diff;
chunk_complement->start = chunk->start + chunk->size;
auto work_list = heap->m_allocated_chunks;
mark(stack_bottom, stack_top, work_list);
heap->m_freed_chunks.erase(iter);
heap->m_freed_chunks.push_back(chunk_complement);
heap->m_allocated_chunks.push_back(chunk);
sweep(heap);
return chunk->start;
}
else if (chunk->size == size)
{
// Reuse the whole chunk
heap->m_freed_chunks.erase(iter);
heap->m_allocated_chunks.push_back(chunk);
return chunk->start;
}
}
return nullptr;
}
free(heap);
}
/**
* Collection phase of the garbage collector. When
* an allocation is requested and there is no space
* left on the heap, a collection is triggered. This
* function is private so that the user cannot trigger
* a collection unneccessarily.
*/
void Heap::collect()
{
// Get instance
auto heap = Heap::the();
/**
* Iterates through the stack, if an element on the stack points to a chunk,
* called a root chunk, that chunk is marked (i.e. reachable).
* Then it recursively follows all chunks which are possibly reachable from
* the root chunk and mark those chunks.
* If a chunk is marked it is removed from the worklist, since it's no longer of
* concern for this method.
*
* @param start Pointer to the start of the stack frame.
* @param end Pointer to the end of the stack frame.
* @param worklist The currently allocated chunks, which haven't been marked.
*/
void Heap::mark(uintptr_t *start, const uintptr_t *end, vector<Chunk*> worklist) {
int counter = 0;
// To find adresses thats in the worklist
for (; start < end; start++) {
counter++;
auto it = worklist.begin();
auto stop = worklist.end();
// for (auto it = worklist.begin(); it != worklist.end();) {
while (it != stop) {
Chunk *chunk = *it;
// get current stack
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
auto c_start = reinterpret_cast<uintptr_t>(chunk->start);
auto c_size = reinterpret_cast<uintptr_t>(chunk->size);
auto c_end = reinterpret_cast<uintptr_t>(c_start + c_size);
uintptr_t *stack_top = heap->m_stack_top != nullptr ? heap->m_stack_top : (uintptr_t *)0;
cout << "Start points to:\t" << hex << *start << endl;
cout << "Chunk start:\t\t" << hex << c_start << endl;
cout << "Chunk end:\t\t" << hex << c_end << "\n" << endl;
auto work_list = heap->m_allocated_chunks;
mark(stack_bottom, stack_top, work_list);
// Check if the stack pointer aligns with the chunk
if (c_start <= *start && *start < c_end) {
if (!chunk->marked) {
chunk->marked = true;
// Remove the marked chunk from the worklist
it = worklist.erase(it);
// Recursively call mark, to see if the reachable chunk further points to another chunk
mark((uintptr_t*) c_start, (uintptr_t*) c_end, worklist);
}
else {
++it;
}
}
else {
++it;
}
}
}
cout << "Counter: " << counter << endl;
}
/**
* Sweeps the heap, unmarks the marked chunks for the next cycle,
* adds the unmarked nodes to the list of freed chunks; to be freed.
*
* @param heap Pointer to the heap singleton instance.
*/
void Heap::sweep(Heap *heap) {
auto iter = heap->m_allocated_chunks.begin();
auto stop = heap->m_allocated_chunks.end();
// for (auto it = heap->m_allocated_chunks.begin(); it != heap->m_allocated_chunks.end();) {
while (iter != stop) {
Chunk *chunk = *iter;
sweep(heap);
// Unmark the marked chunks for the next iteration.
if (chunk->marked) {
chunk->marked = false;
++iter;
}
else {
// Add the unmarked chunks to freed chunks and remove from
// the list of allocated chunks
heap->m_freed_chunks.push_back(chunk);
iter = heap->m_allocated_chunks.erase(iter);
}
}
}
free(heap);
}
/**
* Frees chunks that was moved to the list m_freed_chunks
* by the sweep phase. If there are more than a certain
* amount of free chunks, delete the free chunks to
* avoid cluttering.
*
* @param heap Heap singleton instance, only for avoiding
* redundant calls to the singleton get
*/
void Heap::free(Heap *heap) {
if (heap->m_freed_chunks.size() > FREE_THRESH) {
while (heap->m_freed_chunks.size()) {
auto chunk = heap->m_freed_chunks.back();
heap->m_freed_chunks.pop_back();
delete chunk;
}
}
// if there are chunks but not more than FREE_THRESH
else if (heap->m_freed_chunks.size()) {
// essentially, always check for overlap between
// chunks before finishing the allocation
free_overlap(heap);
}
}
/**
* Iterates through the stack, if an element on the stack points to a chunk,
* called a root chunk, that chunk is marked (i.e. reachable).
* Then it recursively follows all chunks which are possibly reachable from
* the root chunk and mark those chunks.
* If a chunk is marked it is removed from the worklist, since it's no longer of
* concern for this method.
*
* @param start Pointer to the start of the stack frame.
* @param end Pointer to the end of the stack frame.
* @param worklist The currently allocated chunks, which haven't been marked.
*/
void Heap::mark(uintptr_t *start, const uintptr_t *end, vector<Chunk *> &worklist)
{
int counter = 0;
// To find adresses thats in the worklist
for (; start < end; start++)
{
counter++;
auto it = worklist.begin();
auto stop = worklist.end();
// for (auto it = worklist.begin(); it != worklist.end();) {
while (it != stop)
{
Chunk *chunk = *it;
/**
* Checks for overlaps between freed chunks of memory
* and removes overlapping chunks while prioritizing
* the chunks at lower addresses.
*
* @param heap Heap singleton instance, only for avoiding
* redundant calls to the singleton get
*
* @note Maybe this should be changed to prioritizing
* larger chunks.
*/
void Heap::free_overlap(Heap *heap) {
std::vector<Chunk *> filtered;
size_t i = 0;
// filtered.push_back(heap->m_freed_chunks.at(i++));
filtered.push_back(getAt(heap->m_freed_chunks, i++));
cout << filtered.back()->start << endl;
for (; i < heap->m_freed_chunks.size(); i++) {
auto prev = filtered.back();
// auto next = heap->m_freed_chunks.at(i);
auto next = getAt(heap->m_freed_chunks, i);
auto p_start = (uintptr_t)(prev->start);
auto p_size = (uintptr_t)(prev->size);
auto n_start = (uintptr_t)(next->start);
if (n_start >= (p_start + p_size)) {
filtered.push_back(next);
}
}
heap->m_freed_chunks.swap(filtered);
}
auto c_start = reinterpret_cast<uintptr_t>(chunk->start);
auto c_size = reinterpret_cast<uintptr_t>(chunk->size);
auto c_end = reinterpret_cast<uintptr_t>(c_start + c_size);
// ----- ONLY DEBUGGING -----------------------------------------------------------------------
cout << "Start points to:\t" << hex << *start << endl;
cout << "Chunk start:\t\t" << hex << c_start << endl;
cout << "Chunk end:\t\t" << hex << c_end << "\n"
<< endl;
/**
* Prints the result of Heap::init() and a dummy value
* for the current stack frame for reference.
*/
void Heap::check_init() {
auto heap = Heap::the();
cout << "Heap addr:\t" << heap << endl;
cout << "GC m_stack_top:\t" << heap->m_stack_top << endl;
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
cout << "GC stack_bottom:\t" << stack_bottom << endl;
}
/**
* Conditional collection, only to be used in debugging
*
* @param flags Bitmap of flags
*/
void Heap::collect(uint flags) {
// Check if the stack pointer aligns with the chunk
if (c_start <= *start && *start < c_end)
{
cout << "DEBUG COLLECT\nFLAGS: ";
if (flags & MARK)
cout << "\n - MARK";
if (flags & SWEEP)
cout << "\n - SWEEP";
if (flags & FREE)
cout << "\n - FREE";
cout << endl;
auto heap = Heap::the();
if (!chunk->marked)
{
chunk->marked = true;
// Remove the marked chunk from the worklist
it = worklist.erase(it);
// Recursively call mark, to see if the reachable chunk further points to another chunk
mark((uintptr_t *)c_start, (uintptr_t *)c_end, worklist);
}
else
{
++it;
}
}
else
{
++it;
}
}
}
cout << "Counter: " << counter << endl;
}
// get the frame adress, whwere local variables and saved registers are located
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
cout << "Stack bottom in collect:\t" << stack_bottom << endl;
uintptr_t *stack_top;
/**
* Sweeps the heap, unmarks the marked chunks for the next cycle,
* adds the unmarked nodes to the list of freed chunks; to be freed.
*
* @param heap Pointer to the heap singleton instance.
*/
void Heap::sweep(Heap *heap)
{
auto iter = heap->m_allocated_chunks.begin();
auto stop = heap->m_allocated_chunks.end();
// for (auto it = heap->m_allocated_chunks.begin(); it != heap->m_allocated_chunks.end();) {
while (iter != stop)
{
Chunk *chunk = *iter;
if (heap->m_stack_top != nullptr)
stack_top = heap->m_stack_top;
else
stack_top = (uintptr_t *) stack_bottom + 80; // dummy value
// Unmark the marked chunks for the next iteration.
if (chunk->marked)
{
chunk->marked = false;
++iter;
}
else
{
// Add the unmarked chunks to freed chunks and remove from
// the list of allocated chunks
heap->m_freed_chunks.push_back(chunk);
iter = heap->m_allocated_chunks.erase(iter);
}
}
}
cout << "Stack end in collect:\t " << stack_top << endl;
auto work_list = heap->m_allocated_chunks;
/**
* Frees chunks that was moved to the list m_freed_chunks
* by the sweep phase. If there are more than a certain
* amount of free chunks, delete the free chunks to
* avoid cluttering.
*
* @param heap Heap singleton instance, only for avoiding
* redundant calls to the singleton get
*/
void Heap::free(Heap *heap)
{
if (heap->m_freed_chunks.size() > FREE_THRESH)
{
while (heap->m_freed_chunks.size())
{
auto chunk = heap->m_freed_chunks.back();
heap->m_freed_chunks.pop_back();
delete chunk;
}
}
// if there are chunks but not more than FREE_THRESH
else if (heap->m_freed_chunks.size())
{
// essentially, always check for overlap between
// chunks before finishing the allocation
free_overlap(heap);
}
}
if (flags & MARK) {
mark(stack_bottom, stack_top, work_list);
}
/**
* Checks for overlaps between freed chunks of memory
* and removes overlapping chunks while prioritizing
* the chunks at lower addresses.
*
* @param heap Heap singleton instance, only for avoiding
* redundant calls to the singleton get
*
* @note Maybe this should be changed to prioritizing
* larger chunks.
*/
void Heap::free_overlap(Heap *heap)
{
std::vector<Chunk *> filtered;
size_t i = 0;
// filtered.push_back(heap->m_freed_chunks.at(i++));
filtered.push_back(getAt(heap->m_freed_chunks, i++));
cout << filtered.back()->start << endl;
for (; i < heap->m_freed_chunks.size(); i++)
{
auto prev = filtered.back();
// auto next = heap->m_freed_chunks.at(i);
auto next = getAt(heap->m_freed_chunks, i);
auto p_start = (uintptr_t)(prev->start);
auto p_size = (uintptr_t)(prev->size);
auto n_start = (uintptr_t)(next->start);
if (n_start >= (p_start + p_size))
{
filtered.push_back(next);
}
}
heap->m_freed_chunks.swap(filtered);
}
if (flags & SWEEP) {
sweep(heap);
}
if (flags & FREE) {
free(heap);
}
}
// ----- ONLY DEBUGGING -----------------------------------------------------------------------
// Mark child references from the root references
void mark_test(vector<Chunk *> worklist) {
while (worklist.size() > 0) {
Chunk *ref = worklist.back();
worklist.pop_back();
Chunk *child = (Chunk*) ref; // this is probably not correct
if (child != nullptr && !child->marked) {
child->marked = true;
worklist.push_back(child);
mark_test(worklist);
}
}
}
/**
* Prints the result of Heap::init() and a dummy value
* for the current stack frame for reference.
*/
void Heap::check_init()
{
auto heap = Heap::the();
cout << "Heap addr:\t" << heap << "\n";
cout << "GC m_stack_top:\t" << heap->m_stack_top << "\n";
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
cout << "GC stack_bottom:\t" << stack_bottom << endl;
}
// Mark the root references and look for child references to them
void mark_from_roots(uintptr_t *start, const uintptr_t *end) {
vector<Chunk *> worklist;
for (;start > end; start --) {
if (*start % 8 == 0) { // all pointers must be aligned as double words
Chunk *ref = (Chunk*) *start;
if (ref != nullptr && !ref->marked) {
ref->marked = true;
worklist.push_back(ref);
mark_test(worklist);
}
}
}
}
/**
* Conditional collection, only to be used in debugging
*
* @param flags Bitmap of flags
*/
void Heap::collect(uint flags)
{
// For testing purposes
void Heap::print_line(Chunk *chunk) {
cout << "Marked: " << chunk->marked << "\nStart adr: " << chunk->start << "\nSize: " << chunk->size << " B\n" << endl;
}
cout << "DEBUG COLLECT\nFLAGS: ";
if (flags & MARK)
cout << "\n - MARK";
if (flags & SWEEP)
cout << "\n - SWEEP";
if (flags & FREE)
cout << "\n - FREE";
cout << "\n";
void Heap::print_worklist(std::vector<Chunk *> list) {
for (auto cp : list) {
cout << "Chunk at:\t" << cp->start << "\nSize:\t\t" << cp->size << endl;
}
}
auto heap = Heap::the();
void Heap::print_contents() {
auto heap = Heap::the();
if (heap->m_allocated_chunks.size()) {
cout << "\nALLOCATED CHUNKS #" << dec << heap->m_allocated_chunks.size() << endl;
for (auto chunk : heap->m_allocated_chunks) {
print_line(chunk);
}
} else {
cout << "NO ALLOCATIONS\n" << endl;
}
if (heap->m_freed_chunks.size()) {
cout << "\nFREED CHUNKS #" << dec << heap->m_freed_chunks.size() << endl;
for (auto fchunk : heap->m_freed_chunks) {
print_line(fchunk);
}
} else {
cout << "NO FREED CHUNKS" << endl;
}
}
// get the frame adress, whwere local variables and saved registers are located
auto stack_bottom = reinterpret_cast<uintptr_t *>(__builtin_frame_address(0));
cout << "Stack bottom in collect:\t" << stack_bottom << "\n";
uintptr_t *stack_top = heap->m_stack_top;
void Heap::set_profiler(bool mode) {
auto heap = Heap::the();
heap->m_profiler_enable = mode;
}
cout << "Stack end in collect:\t " << stack_top << endl;
auto work_list = heap->m_allocated_chunks;
if (flags & MARK)
mark(stack_bottom, stack_top, work_list);
if (flags & SWEEP)
sweep(heap);
if (flags & FREE)
free(heap);
}
// Mark child references from the root references
void mark_test(vector<Chunk *> &worklist)
{
while (worklist.size() > 0)
{
Chunk *ref = worklist.back();
worklist.pop_back();
Chunk *child = (Chunk *)ref; // this is probably not correct
if (child != nullptr && !child->marked)
{
child->marked = true;
worklist.push_back(child);
mark_test(worklist);
}
}
}
// Mark the root references and look for child references to them
void mark_from_roots(uintptr_t *start, const uintptr_t *end)
{
vector<Chunk *> worklist;
for (; start > end; start--)
{
if (*start % 8 == 0)
{ // all pointers must be aligned as double words
Chunk *ref = (Chunk *)*start;
if (ref != nullptr && !ref->marked)
{
ref->marked = true;
worklist.push_back(ref);
mark_test(worklist);
}
}
}
}
// For testing purposes
void Heap::print_line(Chunk *chunk)
{
cout << "Marked: " << chunk->marked << "\nStart adr: " << chunk->start << "\nSize: " << chunk->size << " B\n"
<< endl;
}
void Heap::print_worklist(std::vector<Chunk *> &list)
{
for (auto cp : list)
cout << "Chunk at:\t" << cp->start << "\nSize:\t\t" << cp->size << "\n";
cout << endl;
}
void Heap::print_contents()
{
auto heap = Heap::the();
if (heap->m_allocated_chunks.size())
{
cout << "\nALLOCATED CHUNKS #" << dec << heap->m_allocated_chunks.size() << endl;
for (auto chunk : heap->m_allocated_chunks)
print_line(chunk);
}
else
{
cout << "NO ALLOCATIONS\n" << endl;
}
if (heap->m_freed_chunks.size())
{
cout << "\nFREED CHUNKS #" << dec << heap->m_freed_chunks.size() << endl;
for (auto fchunk : heap->m_freed_chunks)
print_line(fchunk);
}
else
{
cout << "NO FREED CHUNKS" << endl;
}
}
void Heap::set_profiler(bool mode)
{
auto heap = Heap::the();
heap->m_profiler_enable = mode;
}
}