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cyclone/gc.c
Justin Ethier c550b15f3a Issue #150 - Inefficient (but working) thread-join!
2017-06-17 01:36:47 -04:00

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/**
* Cyclone Scheme
* https://github.com/justinethier/cyclone
*
* Copyright (c) 2015-2016, Justin Ethier
* All rights reserved.
*
* Heap garbage collector used by the Cyclone runtime for major collections.
*
* Tracing GC algorithm is based on the one from "Implementing an on-the-fly
* garbage collector for Java", by Domani et al.
*
* The heap implementation (alloc / sweep, etc) is based on code from Chibi Scheme.
*
* Note there is also a minor GC (in runtime.c) that collects objects allocated
* on the stack, based on "Cheney on the MTA" (but without the copying collector).
*/
#include <ck_array.h>
#include <ck_pr.h>
#include "cyclone/types.h"
#include <stdint.h>
#include <time.h>
//#define DEBUG_THREADS // Debugging!!!
#ifdef DEBUG_THREADS
#include <sys/syscall.h> /* Linux-only? */
#endif
/* HEAP definitions, based off heap from Chibi scheme */
#define gc_heap_first_block(h) ((object)(h->data + gc_heap_align(gc_free_chunk_size)))
#define gc_heap_last_block(h) ((object)((char*)h->data + h->size - gc_heap_align(gc_free_chunk_size)))
#define gc_heap_end(h) ((object)((char*)h->data + h->size))
#define gc_heap_pad_size(s) (sizeof(struct gc_heap_t) + (s) + gc_heap_align(1))
#define gc_free_chunk_size (sizeof(gc_free_list))
#define gc_align(n, bits) (((n)+(1<<(bits))-1)&(((uintptr_t)-1)-((1<<(bits))-1)))
// 64-bit is 3, 32-bit is 2
//#define gc_word_align(n) gc_align((n), 2)
#define gc_heap_align(n) gc_align(n, 5)
////////////////////
// Global variables
// Note: will need to use atomics and/or locking to access any
// variables shared between threads
static int gc_color_mark = 1; // Black, is swapped during GC
static int gc_color_clear = 3; // White, is swapped during GC
// unfortunately this had to be split up; const colors are located in types.h
static int gc_status_col = STATUS_SYNC1;
static int gc_stage = STAGE_RESTING;
// Does not need sync, only used by collector thread
static void **mark_stack = NULL;
static int mark_stack_len = 0;
static int mark_stack_i = 0;
// Data for the "main" thread which is guaranteed to always be there.
// Per SRFI 18:
// All threads are terminated when the primordial
// thread terminates (normally or not).
static gc_thread_data *primordial_thread = NULL;
/** Data for each individual mutator thread */
ck_array_t Cyc_mutators, old_mutators;
static pthread_mutex_t mutators_lock;
static void my_free(void *p, size_t m, bool d)
{
free(p);
return;
}
static void *my_malloc(size_t b)
{
return malloc(b);
}
static void *my_realloc(void *r, size_t a, size_t b, bool d)
{
return realloc(r, b);
}
static struct ck_malloc my_allocator = {
.malloc = my_malloc,
.free = my_free,
.realloc = my_realloc
};
#if GC_DEBUG_TRACE
static double allocated_obj_counts[25] = {
0,0,0,0,0,
0,0,0,0,0,
0,0,0,0,0,
0,0,0,0,0,
0,0,0,0,0};
// TODO: allocated object sizes (EG: 32, 64, etc).
static double allocated_heap_counts[4] = {0, 0, 0, 0};
void print_allocated_obj_counts()
{
int i;
fprintf(stderr, "Allocated objects:\n");
fprintf(stderr, "Tag, Allocations\n");
for (i = 0; i < 25; i++){
fprintf(stderr, "%d, %lf\n", i, allocated_obj_counts[i]);
}
fprintf(stderr, "Allocated heaps:\n");
fprintf(stderr, "Heap, Allocations\n");
for (i = 0; i < 4; i++){
fprintf(stderr, "%d, %lf\n", i, allocated_heap_counts[i]);
}
}
void print_current_time()
{
time_t rawtime;
struct tm * timeinfo;
time ( &rawtime );
timeinfo = localtime ( &rawtime );
fprintf(stderr, "%s", asctime (timeinfo));
}
#endif
/////////////
// Functions
/**
* @brief Perform one-time initialization before mutators can be executed
*/
void gc_initialize(void)
{
if (ck_array_init(&Cyc_mutators, CK_ARRAY_MODE_SPMC, &my_allocator, 10) == 0) {
fprintf(stderr, "Unable to initialize mutator array\n");
exit(1);
}
if (ck_array_init(&old_mutators, CK_ARRAY_MODE_SPMC, &my_allocator, 10) == 0) {
fprintf(stderr, "Unable to initialize mutator array\n");
exit(1);
}
// Initialize collector's mark stack
mark_stack_len = 128;
mark_stack = vpbuffer_realloc(mark_stack, &(mark_stack_len));
// Here is as good a place as any to do this...
if (pthread_mutex_init(&(mutators_lock), NULL) != 0) {
fprintf(stderr, "Unable to initialize mutators_lock mutex\n");
exit(1);
}
}
/**
* @brief Add data for a new mutator
* @param thd Thread data for the mutator
*/
void gc_add_mutator(gc_thread_data * thd)
{
pthread_mutex_lock(&mutators_lock);
if (ck_array_put_unique(&Cyc_mutators, (void *)thd) < 0) {
fprintf(stderr, "Unable to allocate memory for a new thread, exiting\n");
exit(1);
}
ck_array_commit(&Cyc_mutators);
pthread_mutex_unlock(&mutators_lock);
// Main thread is always the first one added
if (primordial_thread == NULL) {
primordial_thread = thd;
}
}
/**
* @brief Remove selected mutator from the mutator list.
* This is done for terminated threads. Note data is queued to be
* freed, to prevent accidentally freeing it while the collector
* thread is potentially accessing it.
* @param thd Thread data for the mutator
*/
void gc_remove_mutator(gc_thread_data * thd)
{
pthread_mutex_lock(&mutators_lock);
if (!ck_array_remove(&Cyc_mutators, (void *)thd)) {
fprintf(stderr, "Unable to remove thread data, exiting\n");
exit(1);
}
ck_array_commit(&Cyc_mutators);
// Place on list of old mutators to cleanup
if (ck_array_put_unique(&old_mutators, (void *)thd) < 0) {
fprintf(stderr, "Unable to add thread data to GC list, existing\n");
exit(1);
}
ck_array_commit(&old_mutators);
pthread_mutex_unlock(&mutators_lock);
}
int gc_is_mutator_active(gc_thread_data *thd)
{
ck_array_iterator_t iterator;
gc_thread_data *m;
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
if (m == thd) {
return 1;
}
}
return 0;
}
/**
* @brief Free thread data for all terminated mutators
*/
void gc_free_old_thread_data()
{
ck_array_iterator_t iterator;
gc_thread_data *m;
int freed = 0;
pthread_mutex_lock(&mutators_lock);
CK_ARRAY_FOREACH(&old_mutators, &iterator, &m) {
//printf("JAE DEBUG - freeing old thread data...");
gc_thread_data_free(m);
if (!ck_array_remove(&old_mutators, (void *)m)) {
fprintf(stderr, "Error removing old mutator data\n");
exit(1);
}
freed = 1;
//printf(" done\n");
}
if (freed) {
ck_array_commit(&old_mutators);
//printf("commited old mutator data deletions\n");
}
pthread_mutex_unlock(&mutators_lock);
}
/**
* @brief Create a new heap page.
* The caller must hold the necessary locks.
* @param heap_type Define the size of objects that will be allocated on this heap
* @param size Requested size (unpadded) of the heap
* @param max_size Define the heap page max size parameter
* @param chunk_size Define the heap chunk size parameter
* @param thd Calling mutator's thread data object
* @return Pointer to the newly allocated heap page, or NULL
* if the allocation failed.
*/
gc_heap *gc_heap_create(int heap_type, size_t size, size_t max_size,
size_t chunk_size, gc_thread_data *thd)
{
gc_free_list *free, *next;
gc_heap *h;
size_t padded_size = gc_heap_pad_size(size);
h = malloc(padded_size); // TODO: mmap?
if (!h)
return NULL;
h->type = heap_type;
h->size = size;
h->ttl = 10;
h->next_free = h;
h->last_alloc_size = 0;
//h->free_size = size;
ck_pr_add_ptr(&(thd->cached_heap_total_sizes[heap_type]), size);
ck_pr_add_ptr(&(thd->cached_heap_free_sizes[heap_type]), size);
h->chunk_size = chunk_size;
h->max_size = max_size;
h->data = (char *)gc_heap_align(sizeof(h->data) + (uintptr_t) & (h->data));
h->next = NULL;
free = h->free_list = (gc_free_list *) h->data;
next = (gc_free_list *) (((char *)free) + gc_heap_align(gc_free_chunk_size));
free->size = 0; // First one is just a dummy record
free->next = next;
next->size = size - gc_heap_align(gc_free_chunk_size);
next->next = NULL;
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG h->data addr: %p\n", &(h->data));
fprintf(stderr, "DEBUG h->data addr: %p\n", h->data);
fprintf(stderr, ("heap: %p-%p data: %p-%p size: %zu\n"),
h, ((char *)h) + gc_heap_pad_size(size), h->data, h->data + size,
size);
fprintf(stderr, ("first: %p end: %p\n"), (object) gc_heap_first_block(h),
(object) gc_heap_end(h));
fprintf(stderr, ("free1: %p-%p free2: %p-%p\n"), free,
((char *)free) + free->size, next, ((char *)next) + next->size);
#endif
return h;
}
/**
* @brief Free a page of the heap
* @param page Page to free
* @param prev_page Previous page in the heap
* @return Previous page if successful, NULL otherwise
*/
gc_heap *gc_heap_free(gc_heap *page, gc_heap *prev_page)
{
// At least for now, do not free first page
if (prev_page == NULL || page == NULL) {
return NULL;
}
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG freeing heap type %d page at addr: %p\n", page->type, page);
#endif
prev_page->next = page->next;
free(page);
return prev_page;
}
/**
* @brief Determine if a heap page is empty
* @param h Heap to inspect. The caller should acquire the necessary lock
* on this heap.
* @return A truthy value if the heap is empty, 0 otherwise.
*/
int gc_is_heap_empty(gc_heap *h)
{
gc_free_list *f;
if (!h || !h->free_list) return 0;
f = h->free_list;
if (f->size != 0 || !f->next) return 0;
f = f->next;
return (f->size + gc_heap_align(gc_free_chunk_size)) == h->size;
}
/**
* @brief Print heap usage information. Before calling this function the
* current thread must have the heap lock
* @param h Heap to analyze.
*/
void gc_print_stats(gc_heap * h)
{
gc_free_list *f;
unsigned int free, free_chunks, free_min, free_max;
int heap_is_empty;
for (; h; h = h->next) {
free = 0;
free_chunks = 0;
free_min = h->size;
free_max = 0;
for (f = h->free_list; f; f = f->next) {
free += f->size;
free_chunks++;
if (f->size < free_min && f->size > 0)
free_min = f->size;
if (f->size > free_max)
free_max = f->size;
}
if (free == 0){ // No free chunks
free_min = 0;
}
heap_is_empty = gc_is_heap_empty(h);
fprintf(stderr,
"Heap type=%d, page size=%u, is empty=%d, used=%u, free=%u, free chunks=%u, min=%u, max=%u\n",
h->type, h->size, heap_is_empty, h->size - free, free, free_chunks, free_min, free_max);
}
}
/**
* @brief Copy given object into given heap object
* @param dest Pointer to destination heap memory slot
* @param obj Object to copy
* @param thd Thread data object for the applicable mutator
* @return The appropriate pointer to use for `obj`
*
* NOTE: There is no additional type checking because this function is
* called from `gc_move` which already does that.
*/
char *gc_copy_obj(object dest, char *obj, gc_thread_data * thd)
{
#if GC_DEBUG_TRACE
allocated_obj_counts[type_of(obj)]++;
#endif
switch (type_of(obj)) {
case closureN_tag:{
int i;
closureN_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = closureN_tag;
hp->fn = ((closureN) obj)->fn;
hp->num_args = ((closureN) obj)->num_args;
hp->num_elements = ((closureN) obj)->num_elements;
hp->elements = (object *) (((char *)hp) + sizeof(closureN_type));
for (i = 0; i < hp->num_elements; i++) {
hp->elements[i] = ((closureN) obj)->elements[i];
}
return (char *)hp;
}
case closure0_tag:{
closure0_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = closure0_tag;
hp->fn = ((closure0) obj)->fn;
hp->num_args = ((closure0) obj)->num_args;
return (char *)hp;
}
case pair_tag:{
list hp = dest;
hp->hdr.mark = thd->gc_alloc_color;
type_of(hp) = pair_tag;
car(hp) = car(obj);
cdr(hp) = cdr(obj);
return (char *)hp;
}
case string_tag:{
char *s;
string_type *hp = dest;
s = ((char *)hp) + sizeof(string_type);
memcpy(s, string_str(obj), string_len(obj) + 1);
mark(hp) = thd->gc_alloc_color;
type_of(hp) = string_tag;
string_len(hp) = string_len(obj);
string_str(hp) = s;
return (char *)hp;
}
case double_tag:{
double_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = double_tag;
hp->value = ((double_type *) obj)->value;
return (char *)hp;
}
case vector_tag:{
int i;
vector_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = vector_tag;
hp->num_elements = ((vector) obj)->num_elements;
hp->elements = (object *) (((char *)hp) + sizeof(vector_type));
for (i = 0; i < hp->num_elements; i++) {
hp->elements[i] = ((vector) obj)->elements[i];
}
return (char *)hp;
}
case bytevector_tag:{
bytevector_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = bytevector_tag;
hp->len = ((bytevector) obj)->len;
hp->data = (((char *)hp) + sizeof(bytevector_type));
memcpy(hp->data, ((bytevector) obj)->data, hp->len);
return (char *)hp;
}
case port_tag:{
port_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = port_tag;
hp->fp = ((port_type *) obj)->fp;
hp->mode = ((port_type *) obj)->mode;
hp->mem_buf = ((port_type *)obj)->mem_buf;
hp->mem_buf_len = ((port_type *)obj)->mem_buf_len;
return (char *)hp;
}
case bignum_tag:{
bignum_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = bignum_tag;
((bignum_type *)hp)->bn.used = ((bignum_type *)obj)->bn.used;
((bignum_type *)hp)->bn.alloc = ((bignum_type *)obj)->bn.alloc;
((bignum_type *)hp)->bn.sign = ((bignum_type *)obj)->bn.sign;
((bignum_type *)hp)->bn.dp = ((bignum_type *)obj)->bn.dp;
return (char *)hp;
}
case cvar_tag:{
cvar_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = cvar_tag;
hp->pvar = ((cvar_type *) obj)->pvar;
return (char *)hp;
}
case mutex_tag:{
mutex_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = mutex_tag;
// NOTE: don't copy mutex itself, caller will do that (this is a special case)
return (char *)hp;
}
case cond_var_tag:{
cond_var_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = cond_var_tag;
// NOTE: don't copy cond_var itself, caller will do that (this is a special case)
return (char *)hp;
}
case macro_tag:{
macro_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = macro_tag;
hp->fn = ((macro) obj)->fn;
hp->num_args = ((macro) obj)->num_args;
return (char *)hp;
}
case closure1_tag:{
closure1_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = closure1_tag;
hp->fn = ((closure1) obj)->fn;
hp->num_args = ((closure1) obj)->num_args;
hp->element = ((closure1) obj)->element;
return (char *)hp;
}
case c_opaque_tag:{
c_opaque_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = c_opaque_tag;
hp->ptr = ((c_opaque_type *) obj)->ptr;
return (char *)hp;
}
case forward_tag:
return (char *)forward(obj);
case eof_tag:
case primitive_tag:
case boolean_tag:
case symbol_tag:
break;
case integer_tag:{
integer_type *hp = dest;
mark(hp) = thd->gc_alloc_color;
type_of(hp) = integer_tag;
hp->value = ((integer_type *) obj)->value;
return (char *)hp;
}
default:
fprintf(stderr, "gc_copy_obj: bad tag obj=%p obj.tag=%d\n", (object) obj,
type_of(obj));
exit(1);
}
return (char *)obj;
}
/**
* @brief Grow a heap by allocating a new page.
* @param h Heap to be expanded
* @param heap_type Define the size of objects that will be allocated on this heap
* @param size Not applicable, can set to 0
* @param chunk_size Heap chunk size, or 0 if not applicable
* @param thd Thread data for the mutator using this heap
* @return A true value if the heap was grown, or 0 otherwise
*
* Heaps are increased in size by adding a newly-allocated page at the
* end of the heap's linked list.
*
* Page size is determined by starting at the minimum page size and
* increasing size using the Fibonnaci Sequence until reaching the
* max size.
*/
int gc_grow_heap(gc_heap * h, int heap_type, size_t size, size_t chunk_size, gc_thread_data *thd)
{
size_t /*cur_size,*/ new_size;
gc_heap *h_last = h, *h_new;
pthread_mutex_lock(&(thd->heap_lock));
// Compute size of new heap page
if (heap_type == HEAP_HUGE) {
new_size = gc_heap_align(size) + 128;
while (h_last->next) {
h_last = h_last->next;
}
} else {
// Grow heap gradually using fibonnaci sequence.
size_t prev_size = GROW_HEAP_BY_SIZE;
new_size = 0;
while (h_last->next) {
if (new_size < HEAP_SIZE) {
new_size = prev_size + h_last->size;
prev_size = h_last->size;
if (new_size > HEAP_SIZE) {
new_size = HEAP_SIZE;
}
} else {
new_size = HEAP_SIZE;
}
h_last = h_last->next;
}
if (new_size == 0) {
new_size = prev_size + h_last->size;
}
// Fast-track heap page size if allocating a large block
if (new_size < size && size < HEAP_SIZE) {
new_size = HEAP_SIZE;
}
#if GC_DEBUG_TRACE
fprintf(stderr, "Growing heap %d new page size = %zu\n", heap_type,
new_size);
#endif
}
// h_last = gc_heap_last(h);
// cur_size = h_last->size;
// new_size = cur_size; //gc_heap_align(((cur_size > size) ? cur_size : size) * 2);
// allocate larger pages if size will not fit on the page
//new_size = gc_heap_align(((cur_size > size) ? cur_size : size));
// Done with computing new page size
h_new = gc_heap_create(heap_type, new_size, h_last->max_size, chunk_size, thd);
h_last->next = h_new;
pthread_mutex_unlock(&(thd->heap_lock));
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - grew heap\n");
#endif
return (h_new != NULL);
}
/**
* @brief Attempt to allocate a new heap slot for the given object
* @param h Heap to allocate from
* @param heap_type Define the size of objects that will be allocated on this heap
* @param size Size of the requested object, in bytes
* @param obj Object containing data that will be copied to the heap
* @param thd Thread data for the mutator using this heap
* @return Pointer to the newly-allocated object, or `NULL` if allocation failed
*
* This function will fail if there is no space on the heap for the
* requested object.
*/
void *gc_try_alloc(gc_heap * h, int heap_type, size_t size, char *obj,
gc_thread_data * thd)
{
gc_heap *h_passed = h;
gc_free_list *f1, *f2, *f3;
pthread_mutex_lock(&(thd->heap_lock));
// Start searching from the last heap page we had a successful
// allocation from, unless the current request is for a smaller
// block in which case there may be available memory closer to
// the start of the heap.
if (size >= h->last_alloc_size) {
h = h->next_free;
}
for (; h; h = h->next) { // All heaps
// TODO: chunk size (ignoring for now)
for (f1 = h->free_list, f2 = f1->next; f2; f1 = f2, f2 = f2->next) { // all free in this heap
if (f2->size >= size) { // Big enough for request
// TODO: take whole chunk or divide up f2 (using f3)?
if (f2->size >= (size + gc_heap_align(1) /* min obj size */ )) {
f3 = (gc_free_list *) (((char *)f2) + size);
f3->size = f2->size - size;
f3->next = f2->next;
f1->next = f3;
} else { /* Take the whole chunk */
f1->next = f2->next;
}
if (heap_type != HEAP_HUGE) {
// Copy object into heap now to avoid any uninitialized memory issues
gc_copy_obj(f2, obj, thd);
//h->free_size -= gc_allocated_bytes(obj, NULL, NULL);
ck_pr_sub_ptr(&(thd->cached_heap_free_sizes[heap_type]), size);
} else {
ck_pr_add_int(&(thd->heap_num_huge_allocations), 1);
}
h_passed->next_free = h;
h_passed->last_alloc_size = size;
pthread_mutex_unlock(&(thd->heap_lock));
return f2;
}
}
}
pthread_mutex_unlock(&(thd->heap_lock));
return NULL;
}
/**
* @brief A convenience function for allocating bignums
* @param data The mutator's thread data object
* @return Pointer to a heap object for the bignum
*/
void *gc_alloc_bignum(gc_thread_data *data)
{
int heap_grown, result;
bignum_type *bn;
bignum_type tmp;
tmp.hdr.mark = gc_color_red;
tmp.hdr.grayed = 0;
tmp.tag = bignum_tag;
bn = gc_alloc(((gc_thread_data *)data)->heap, sizeof(bignum_type), (char *)(&tmp), (gc_thread_data *)data, &heap_grown);
if ((result = mp_init(&bignum_value(bn))) != MP_OKAY) {
fprintf(stderr, "Error initializing number %s",
mp_error_to_string(result));
exit(1);
}
return bn;
}
/**
* @brief A helper function to create a heap-allocated copy of a bignum
* @param data The mutator's thread data object
* @param src The bignum instance to copy to the heap
* @return Pointer to the heap object
*/
void *gc_alloc_from_bignum(gc_thread_data *data, bignum_type *src)
{
int heap_grown;
return gc_alloc(((gc_thread_data *)data)->heap, sizeof(bignum_type), (char *)(src), (gc_thread_data *)data, &heap_grown);
}
/**
* @brief Allocate memory on the heap for an object
* @param hrt The root of the heap to allocate from
* @param size Size of the object to allocate
* @param obj Object containing data to copy to the heap
* @param thd The requesting mutator's thread data object
* @param heap_grown Pointer to an "out" parameter that will be set to
* `1` if the heap is grown in size.
* @return Pointer to the heap object
*
* This function will attempt to grow the heap if it is full, and will
* terminate the program if the OS is out of memory.
*/
void *gc_alloc(gc_heap_root * hrt, size_t size, char *obj, gc_thread_data * thd,
int *heap_grown)
{
void *result = NULL;
gc_heap *h = NULL;
int heap_type;
// TODO: check return value, if null (could not alloc) then
// run a collection and check how much free space there is. if less
// the allowed ratio, try growing heap.
// then try realloc. if cannot alloc now, then throw out of memory error
size = gc_heap_align(size);
if (size <= 32) {
heap_type = HEAP_SM;
} else if (size <= 64) {
heap_type = HEAP_64;
// Only use this heap on 64-bit platforms, where larger objs are used more often
// Code from http://stackoverflow.com/a/32717129/101258
#if INTPTR_MAX == INT64_MAX
} else if (size <= 96) {
heap_type = HEAP_96;
#endif
} else if (size >= MAX_STACK_OBJ) {
heap_type = HEAP_HUGE;
} else {
heap_type = HEAP_REST;
}
h = hrt->heap[heap_type];
#if GC_DEBUG_TRACE
allocated_heap_counts[heap_type]++;
#endif
result = gc_try_alloc(h, heap_type, size, obj, thd);
if (!result) {
// A vanilla mark&sweep collector would collect now, but unfortunately
// we can't do that because we have to go through multiple stages, some
// of which are asynchronous. So... no choice but to grow the heap.
gc_grow_heap(h, heap_type, size, 0, thd);
*heap_grown = 1;
result = gc_try_alloc(h, heap_type, size, obj, thd);
if (!result) {
fprintf(stderr, "out of memory error allocating %zu bytes\n", size);
fprintf(stderr, "Heap type %d diagnostics:\n", heap_type);
pthread_mutex_lock(&(thd->heap_lock));
gc_print_stats(h);
pthread_mutex_unlock(&(thd->heap_lock)); // why not
exit(1); // could throw error, but OOM is a major issue, so...
}
}
#if GC_DEBUG_VERBOSE
fprintf(stderr, "alloc %p size = %zu, obj=%p, tag=%d, mark=%d\n", result,
size, obj, type_of(obj), mark(((object) result)));
// Debug check, should no longer be necessary
//if (is_value_type(result)) {
// printf("Invalid allocated address - is a value type %p\n", result);
//}
#endif
return result;
}
/**
* @brief Get the number of bytes that will be allocated for `obj`.
* @param obj Object to inspect
* @param q Previous free list pointer, set to `NULL` if not applicable
* @param r Next free list pointer, set to `NULL` if not applicable
* @return Number of bytes, including any needed for alignment
*/
size_t gc_allocated_bytes(object obj, gc_free_list * q, gc_free_list * r)
{
tag_type t;
#if GC_SAFETY_CHECKS
if (is_value_type(obj)) {
fprintf(stderr,
"gc_allocated_bytes - passed value type %p q=[%p, %d] r=[%p, %d]\n",
obj, q, q->size, r, r->size);
exit(1);
}
#endif
t = type_of(obj);
if (t == pair_tag)
return gc_heap_align(sizeof(pair_type));
if (t == closureN_tag) {
return gc_heap_align(sizeof(closureN_type) +
sizeof(object) *
((closureN_type *) obj)->num_elements);
}
if (t == double_tag)
return gc_heap_align(sizeof(double_type));
if (t == closure0_tag)
return gc_heap_align(sizeof(closure0_type));
if (t == closure1_tag)
return gc_heap_align(sizeof(closure1_type));
if (t == string_tag) {
return gc_heap_align(sizeof(string_type) + string_len(obj) + 1);
}
if (t == vector_tag) {
return gc_heap_align(sizeof(vector_type) +
sizeof(object) * ((vector_type *) obj)->num_elements);
}
if (t == bytevector_tag) {
return gc_heap_align(sizeof(bytevector_type) +
sizeof(char) * ((bytevector) obj)->len);
}
if (t == macro_tag)
return gc_heap_align(sizeof(macro_type));
if (t == bignum_tag)
return gc_heap_align(sizeof(bignum_type));
if (t == port_tag)
return gc_heap_align(sizeof(port_type));
if (t == cvar_tag)
return gc_heap_align(sizeof(cvar_type));
if (t == c_opaque_tag)
return gc_heap_align(sizeof(c_opaque_type));
if (t == mutex_tag)
return gc_heap_align(sizeof(mutex_type));
if (t == cond_var_tag)
return gc_heap_align(sizeof(cond_var_type));
if (t == integer_tag)
return gc_heap_align(sizeof(integer_type));
fprintf(stderr, "gc_allocated_bytes: unexpected object %p of type %d\n", obj,
t);
exit(1);
return 0;
}
/**
* @brief Get the heap's last page
* @param h Heap to inspect
* @return Pointer to the heap's last page
*
* This function does not do any locking, it is the responsibility of
* the caller to hold the appropriate locks prior to calling.
*/
gc_heap *gc_heap_last(gc_heap * h)
{
while (h->next)
h = h->next;
return h;
}
//size_t gc_heap_total_size(gc_heap * h)
//{
// size_t total_size = 0;
// pthread_mutex_lock(&heap_lock);
// while (h) {
// total_size += h->size;
// h = h->next;
// }
// pthread_mutex_unlock(&heap_lock);
// return total_size;
//}
//
//size_t gc_heap_total_free_size(gc_heap *h)
//{
// size_t total_size = 0;
// pthread_mutex_lock(&heap_lock);
// while(h) {
// total_size += h->free_size;
// h = h->next;
// }
// pthread_mutex_unlock(&heap_lock);
// return total_size;
//}
/**
* @brief A convenient front-end to the actual gc_sweep function.
*/
void gc_collector_sweep()
{
ck_array_iterator_t iterator;
gc_thread_data *m;
gc_heap *h;
int heap_type;
size_t freed_tmp = 0, freed = 0;
#if GC_DEBUG_TRACE
size_t total_size;
size_t total_free;
time_t gc_collector_start = time(NULL);
#endif
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
for (heap_type = 0; heap_type < NUM_HEAP_TYPES; heap_type++) {
h = m->heap->heap[heap_type];
if (h) {
gc_sweep(h, heap_type, &freed_tmp, m);
freed += freed_tmp;
}
}
// TODO: this loop only includes smallest 2 heaps, is that sufficient??
for (heap_type = 0; heap_type < 2; heap_type++) {
while ( ck_pr_load_ptr(&(m->cached_heap_free_sizes[heap_type])) <
(ck_pr_load_ptr(&(m->cached_heap_total_sizes[heap_type])) * GC_FREE_THRESHOLD)) {
#if GC_DEBUG_TRACE
fprintf(stderr, "Less than %f%% of the heap %d is free, growing it\n",
100.0 * GC_FREE_THRESHOLD, heap_type);
#endif
if (heap_type == HEAP_SM) {
gc_grow_heap(m->heap->heap[heap_type], heap_type, 0, 0, m);
} else if (heap_type == HEAP_64) {
gc_grow_heap(m->heap->heap[heap_type], heap_type, 0, 0, m);
} else if (heap_type == HEAP_REST) {
gc_grow_heap(m->heap->heap[heap_type], heap_type, 0, 0, m);
}
}
}
// Clear allocation counts to delay next GC trigger
ck_pr_store_int(&(m->heap_num_huge_allocations), 0);
#if GC_DEBUG_TRACE
total_size = ck_pr_load_ptr(&(m->cached_heap_total_sizes[HEAP_SM])) +
ck_pr_load_ptr(&(m->cached_heap_total_sizes[HEAP_64])) +
#if INTPTR_MAX == INT64_MAX
ck_pr_load_ptr(&(m->cached_heap_total_sizes[HEAP_96])) +
#endif
ck_pr_load_ptr(&(m->cached_heap_total_sizes[HEAP_REST]));
total_free = ck_pr_load_ptr(&(m->cached_heap_free_sizes[HEAP_SM])) +
ck_pr_load_ptr(&(m->cached_heap_free_sizes[HEAP_64])) +
#if INTPTR_MAX == INT64_MAX
ck_pr_load_ptr(&(m->cached_heap_free_sizes[HEAP_96])) +
#endif
ck_pr_load_ptr(&(m->cached_heap_free_sizes[HEAP_REST]));
fprintf(stderr,
"sweep done, total_size = %zu, total_free = %zu, freed = %zu, elapsed = %ld\n",
total_size, total_free, freed,
(time(NULL) - gc_collector_start));
#endif
}
#if GC_DEBUG_TRACE
fprintf(stderr, "all thread heap sweeps done\n");
#endif
}
/**
* @brief Sweep portion of the GC algorithm
* @param h Heap to sweep
* @param heap_type Type of heap, based on object sizes allocated on it
* @param sum_freed_ptr Out parameter tracking the sum of freed data, in bytes.
* This parameter is ignored if NULL is passed.
* @param thd Thread data object for the mutator using this heap
* @return Return the size of the largest object freed, in bytes
*
* This portion of the major GC algorithm is responsible for returning unused
* memory slots to the heap. It is only called by the collector thread after
* the heap has been traced to identify live objects.
*/
size_t gc_sweep(gc_heap * h, int heap_type, size_t * sum_freed_ptr, gc_thread_data *thd)
{
size_t freed, max_freed = 0, heap_freed = 0, sum_freed = 0, size;
object p, end;
gc_free_list *q, *r, *s;
#if GC_DEBUG_SHOW_SWEEP_DIAG
gc_heap *orig_heap_ptr = h;
#endif
gc_heap *prev_h = NULL;
//
// Lock the heap to prevent issues with allocations during sweep
// This coarse-grained lock actually performed better than a fine-grained one.
//
pthread_mutex_lock(&(thd->heap_lock));
h->next_free = h;
h->last_alloc_size = 0;
#if GC_DEBUG_SHOW_SWEEP_DIAG
fprintf(stderr, "\nBefore sweep -------------------------\n");
fprintf(stderr, "Heap %d diagnostics:\n", heap_type);
gc_print_stats(orig_heap_ptr);
#endif
for (; h; prev_h = h, h = h->next) { // All heaps
#if GC_DEBUG_TRACE
fprintf(stderr, "sweep heap %p, size = %zu\n", h, (size_t) h->size);
#endif
p = gc_heap_first_block(h);
q = h->free_list;
end = gc_heap_end(h);
while (p < end) {
// find preceding/succeeding free list pointers for p
for (r = q->next; r && ((char *)r < (char *)p); q = r, r = r->next) ;
if ((char *)r == (char *)p) { // this is a free block, skip it
p = (object) (((char *)p) + r->size);
#if GC_DEBUG_VERBOSE
fprintf(stderr, "skip free block %p size = %zu\n", p, r->size);
#endif
continue;
}
size = gc_heap_align(gc_allocated_bytes(p, q, r));
#if GC_SAFETY_CHECKS
if (!is_object_type(p)) {
fprintf(stderr, "sweep: invalid object at %p", p);
exit(1);
}
if ((char *)q + q->size > (char *)p) {
fprintf(stderr, "bad size at %p < %p + %u", p, q, q->size);
exit(1);
}
if (r && ((char *)p) + size > (char *)r) {
fprintf(stderr, "sweep: bad size at %p + %zu > %p", p, size, r);
exit(1);
}
#endif
if (mark(p) == gc_color_clear) {
#if GC_DEBUG_VERBOSE
fprintf(stderr, "sweep is freeing unmarked obj: %p with tag %d\n", p,
type_of(p));
#endif
mark(p) = gc_color_blue; // Needed?
if (type_of(p) == mutex_tag) {
#if GC_DEBUG_VERBOSE
fprintf(stderr, "pthread_mutex_destroy from sweep\n");
#endif
if (pthread_mutex_destroy(&(((mutex) p)->lock)) != 0) {
fprintf(stderr, "Error destroying mutex\n");
exit(1);
}
} else if (type_of(p) == cond_var_tag) {
#if GC_DEBUG_VERBOSE
fprintf(stderr, "pthread_cond_destroy from sweep\n");
#endif
if (pthread_cond_destroy(&(((cond_var) p)->cond)) != 0) {
fprintf(stderr, "Error destroying condition variable\n");
exit(1);
}
} else if (type_of(p) == bignum_tag) {
// TODO: this is no good if we abandon bignum's on the stack
// in that case the finalizer is never called
#if GC_DEBUG_VERBOSE
fprintf(stderr, "mp_clear from sweep\n");
#endif
mp_clear(&(((bignum_type *)p)->bn));
}
// free p
heap_freed += size;
if (((((char *)q) + q->size) == (char *)p) && (q != h->free_list)) {
/* merge q with p */
if (r && r->size && ((((char *)p) + size) == (char *)r)) {
// ... and with r
q->next = r->next;
freed = q->size + size + r->size;
p = (object) (((char *)p) + size + r->size);
} else {
freed = q->size + size;
p = (object) (((char *)p) + size);
}
q->size = freed;
} else {
s = (gc_free_list *) p;
if (r && r->size && ((((char *)p) + size) == (char *)r)) {
// merge p with r
s->size = size + r->size;
s->next = r->next;
q->next = s;
freed = size + r->size;
} else {
s->size = size;
s->next = r;
q->next = s;
freed = size;
}
p = (object) (((char *)p) + freed);
}
if (freed > max_freed)
max_freed = freed;
} else {
//#if GC_DEBUG_VERBOSE
// fprintf(stderr, "sweep: object is marked %p\n", p);
//#endif
p = (object) (((char *)p) + size);
}
}
//h->free_size += heap_freed;
ck_pr_add_ptr(&(thd->cached_heap_free_sizes[heap_type]), heap_freed);
// Free the heap page if possible.
//
// With huge heaps, this becomes more important. one of the huge
// pages only has one object, so it is likely that the page
// will become free at some point and could be reclaimed.
//
// The newly created flag is used to attempt to avoid situtaions
// where a page is allocated because there is not enough free space,
// but then we do a sweep and see it is empty so we free it, and
// so forth. A better solution might be to keep empty heap pages
// off to the side and only free them if there is enough free space
// remaining without them.
//
// Experimenting with only freeing huge heaps
if (gc_is_heap_empty(h) &&
(h->type == HEAP_HUGE || !(h->ttl--))) {
unsigned int h_size = h->size;
gc_heap *new_h = gc_heap_free(h, prev_h);
if (new_h) { // Ensure free succeeded
h = new_h;
ck_pr_sub_ptr(&(thd->cached_heap_free_sizes[heap_type] ), h_size);
ck_pr_sub_ptr(&(thd->cached_heap_total_sizes[heap_type]), h_size);
}
}
sum_freed += heap_freed;
heap_freed = 0;
}
#if GC_DEBUG_SHOW_SWEEP_DIAG
fprintf(stderr, "\nAfter sweep -------------------------\n");
fprintf(stderr, "Heap %d diagnostics:\n", heap_type);
gc_print_stats(orig_heap_ptr);
#endif
pthread_mutex_unlock(&(thd->heap_lock));
if (sum_freed_ptr)
*sum_freed_ptr = sum_freed;
return max_freed;
}
/**
* @brief Increase the size of the mutator's move buffer
* @param d Mutator's thread data object
*/
void gc_thr_grow_move_buffer(gc_thread_data * d)
{
if (!d)
return;
if (d->moveBufLen == 0) { // Special case
d->moveBufLen = 128;
d->moveBuf = NULL;
} else {
d->moveBufLen *= 2;
}
d->moveBuf = realloc(d->moveBuf, d->moveBufLen * sizeof(void *));
#if GC_DEBUG_TRACE
fprintf(stderr, "grew moveBuffer, len = %d\n", d->moveBufLen);
#endif
}
/**
* @brief Add an object to the move buffer
* @param d Mutator data object containing the buffer
* @param alloci Pointer to the next open slot in the buffer
* @param obj Object to add
*/
void gc_thr_add_to_move_buffer(gc_thread_data * d, int *alloci, object obj)
{
if (*alloci == d->moveBufLen) {
gc_thr_grow_move_buffer(d);
}
d->moveBuf[*alloci] = obj;
(*alloci)++;
}
// END heap definitions
// Tri-color GC section
/////////////////////////////////////////////
// GC functions called by the Mutator threads
/**
* @brief Clear thread data read/write fields
* @param thd Mutator's thread data object
*/
void gc_zero_read_write_counts(gc_thread_data * thd)
{
pthread_mutex_lock(&(thd->lock));
#if GC_SAFETY_CHECKS
if (thd->last_read < thd->last_write) {
fprintf(stderr,
"gc_zero_read_write_counts - last_read (%d) < last_write (%d)\n",
thd->last_read, thd->last_write);
} else if (thd->pending_writes) {
fprintf(stderr,
"gc_zero_read_write_counts - pending_writes (%d) is not zero\n",
thd->pending_writes);
}
#endif
thd->last_write = 0;
thd->last_read = 0;
thd->pending_writes = 0;
pthread_mutex_unlock(&(thd->lock));
}
/**
* @brief Move pending writes to 'last_write'
* @param thd Mutator's thread data object
* @param locked Does the caller hold the mutator lock?
*/
void gc_sum_pending_writes(gc_thread_data * thd, int locked)
{
if (!locked) {
pthread_mutex_lock(&(thd->lock));
}
thd->last_write += thd->pending_writes;
thd->pending_writes = 0;
if (!locked) {
pthread_mutex_unlock(&(thd->lock));
}
}
/**
* @brief Determine if object lives on the thread's stack
* @param thd Mutator's thread data
* @param obj Object to inspect
* @return True if `obj` is on the mutator's stack, false otherwise
*/
int gc_is_stack_obj(gc_thread_data * thd, object obj)
{
char tmp;
object low_limit = &tmp;
object high_limit = thd->stack_start;
return (stack_overflow(low_limit, obj) && stack_overflow(obj, high_limit));
}
/**
* @brief Helper function for `gc_mut_update`
*/
static void mark_stack_or_heap_obj(gc_thread_data * thd, object obj)
{
if (gc_is_stack_obj(thd, obj)) {
// Set object to be marked after moved to heap by next GC.
// This avoids having to recursively examine the stack now,
// which we have to do anyway during minor GC.
grayed(obj) = 1;
} else {
// Value is on the heap, mark gray right now
gc_mark_gray(thd, obj);
}
}
/**
* @brief Write barrier for updates to heap-allocated objects
* @param thd Mutator's thread data
* @param old_obj Old object value prior to the mutation
* @param value New object value
*
* The key for this barrier is to identify stack objects that contain
* heap references, so they can be marked to avoid collection.
*/
void gc_mut_update(gc_thread_data * thd, object old_obj, object value)
{
int //status = ck_pr_load_int(&gc_status_col),
stage = ck_pr_load_int(&gc_stage);
if (ck_pr_load_int(&(thd->gc_status)) != STATUS_ASYNC) {
pthread_mutex_lock(&(thd->lock));
mark_stack_or_heap_obj(thd, old_obj);
mark_stack_or_heap_obj(thd, value);
pthread_mutex_unlock(&(thd->lock));
} else if (stage == STAGE_TRACING) {
//fprintf(stderr, "DEBUG - GC async tracing marking heap obj %p ", old_obj);
//Cyc_display(old_obj, stderr);
//fprintf(stderr, "\n");
pthread_mutex_lock(&(thd->lock));
mark_stack_or_heap_obj(thd, old_obj);
pthread_mutex_unlock(&(thd->lock));
#if GC_DEBUG_VERBOSE
if (is_object_type(old_obj) && mark(old_obj) == gc_color_clear) {
fprintf(stderr,
"added to mark buffer (trace) from write barrier %p:mark %d:",
old_obj, mark(old_obj));
Cyc_display(old_obj, stderr);
fprintf(stderr, "\n");
}
#endif
}
}
/**
* @brief Called by a mutator to cooperate with the collector thread
* @param thd Mutator's thread data
* @param buf_len Number of objects moved to the heap by the mutator during minor GC
*
* This function must be called periodically by each mutator to coordinate
* with the collector. In our implementation it is called after minor GC.
*/
void gc_mut_cooperate(gc_thread_data * thd, int buf_len)
{
int i, status_c, status_m;
#if GC_DEBUG_VERBOSE
int debug_print = 0;
#endif
// Handle any pending marks from write barrier
gc_sum_pending_writes(thd, 0);
// I think below is thread safe, but this code is tricky.
// Worst case should be that some work is done twice if there is
// a race condition
//
// TODO: should use an atomic comparison here
status_c = ck_pr_load_int(&gc_status_col);
status_m = ck_pr_load_int(&(thd->gc_status));
if (status_m != status_c) {
ck_pr_cas_int(&(thd->gc_status), status_m, status_c);
if (status_m == STATUS_ASYNC) {
// Async is done, so clean up old mark data from the last collection
gc_zero_read_write_counts(thd);
} else if (status_m == STATUS_SYNC2) {
#if GC_DEBUG_VERBOSE
debug_print = 1;
#endif
// Mark thread "roots":
// Begin my marking current continuation, which may have already
// been on the heap prior to latest minor GC
pthread_mutex_lock(&(thd->lock));
gc_mark_gray(thd, thd->gc_cont);
for (i = 0; i < thd->gc_num_args; i++) {
gc_mark_gray(thd, thd->gc_args[i]);
}
// Mark thread object, if applicable. Very likely this is its only ref
if (thd->scm_thread_obj) {
gc_mark_gray(thd, thd->scm_thread_obj);
}
if (thd->exception_handler_stack) {
gc_mark_gray(thd, thd->exception_handler_stack);
}
if (thd->param_objs) {
gc_mark_gray(thd, thd->param_objs);
}
// Also, mark everything the collector moved to the heap
for (i = 0; i < buf_len; i++) {
gc_mark_gray(thd, thd->moveBuf[i]);
}
pthread_mutex_unlock(&(thd->lock));
thd->gc_alloc_color = ck_pr_load_int(&gc_color_mark);
}
}
#if GC_DEBUG_VERBOSE
if (debug_print) {
fprintf(stderr, "coop mark gc_cont %p\n", thd->gc_cont);
for (i = 0; i < thd->gc_num_args; i++) {
fprintf(stderr, "coop mark gc_args[%d] %p\n", i, thd->gc_args[i]);
}
for (i = 0; i < buf_len; i++) {
fprintf(stderr, "coop mark from move buf %i %p\n", i, thd->moveBuf[i]);
}
}
#endif
// Initiate collection cycle if free space is too low.
// Threshold is intentially low because we have to go through an
// entire handshake/trace/sweep cycle, ideally without growing heap.
if (ck_pr_load_int(&gc_stage) == STAGE_RESTING &&
((ck_pr_load_ptr(&(thd->cached_heap_free_sizes[HEAP_SM])) <
ck_pr_load_ptr(&(thd->cached_heap_total_sizes[HEAP_SM])) * GC_COLLECTION_THRESHOLD) ||
(ck_pr_load_ptr(&(thd->cached_heap_free_sizes[HEAP_64])) <
ck_pr_load_ptr(&(thd->cached_heap_total_sizes[HEAP_64])) * GC_COLLECTION_THRESHOLD) ||
#if INTPTR_MAX == INT64_MAX
(ck_pr_load_ptr(&(thd->cached_heap_free_sizes[HEAP_96])) <
ck_pr_load_ptr(&(thd->cached_heap_total_sizes[HEAP_96])) * GC_COLLECTION_THRESHOLD) ||
#endif
(ck_pr_load_ptr(&(thd->cached_heap_free_sizes[HEAP_REST])) <
ck_pr_load_ptr(&(thd->cached_heap_total_sizes[HEAP_REST])) * GC_COLLECTION_THRESHOLD) ||
// Separate huge heap threshold since these are typically allocated as whole pages
(ck_pr_load_int(&(thd->heap_num_huge_allocations)) > 100)
)) {
#if GC_DEBUG_TRACE
fprintf(stderr,
"Less than %f%% of the heap is free, initiating collector\n",
100.0 * GC_COLLECTION_THRESHOLD);
#endif
ck_pr_cas_int(&gc_stage, STAGE_RESTING, STAGE_CLEAR_OR_MARKING);
}
}
/////////////////////////////////////////////
// Collector functions
/**
* @brief Mark the given object gray if it is on the heap.
* @param thd Mutator's thread data
* @param obj Object to gray
*
* Note marking is done implicitly by placing it in a buffer,
* to avoid repeated re-scanning.
*
* This function must be executed once the thread lock has been acquired.
*/
void gc_mark_gray(gc_thread_data * thd, object obj)
{
// From what I can tell, no other thread would be modifying
// either object type or mark. Both should be stable once the object is placed
// into the heap, with the collector being the only thread that changes marks.
if (is_object_type(obj) && mark(obj) == gc_color_clear) { // TODO: sync??
// Place marked object in a buffer to avoid repeated scans of the heap.
// TODO:
// Note that ideally this should be a lock-free data structure to make the
// algorithm more efficient. So this code (and the corresponding collector
// trace code) should be converted at some point.
thd->mark_buffer = vpbuffer_add(thd->mark_buffer,
&(thd->mark_buffer_len),
thd->last_write, obj);
(thd->last_write)++; // Already locked, just do it...
}
}
/**
* @brief Add a pending write to the mark buffer.
* @param thd Mutator's thread data
* @param obj Object to gray
*
* These are pended because they are written in a batch during minor GC.
* To prevent race conditions we wait until all of the writes are made before
* updating last write.
*
* TODO: figure out a new name for this function.
*/
void gc_mark_gray2(gc_thread_data * thd, object obj)
{
if (is_object_type(obj) && mark(obj) == gc_color_clear) {
thd->mark_buffer = vpbuffer_add(thd->mark_buffer,
&(thd->mark_buffer_len),
(thd->last_write + thd->pending_writes),
obj);
thd->pending_writes++;
}
}
/**
* @brief "Color" objects gray by adding them to the mark stack for further processing.
* @param parent Parent of object, used for debugging only
* @param obj Object to mark
*
* Note that stack objects are always colored red during creation, so
* they should never be added to the mark stack. Which would be bad because it
* could lead to stack corruption.
*/
#if GC_DEBUG_VERBOSE
static void gc_collector_mark_gray(object parent, object obj)
{
if (is_object_type(obj) && mark(obj) == gc_color_clear) {
mark_stack = vpbuffer_add(mark_stack, &mark_stack_len, mark_stack_i++, obj);
fprintf(stderr, "mark gray parent = %p (%d) obj = %p\n", parent,
type_of(parent), obj);
}
}
#else
//
// Attempt to speed this up by forcing an inline
//
#define gc_collector_mark_gray(parent, gobj) \
if (is_object_type(gobj) && mark(gobj) == gc_color_clear) { \
mark_stack = vpbuffer_add(mark_stack, &mark_stack_len, mark_stack_i++, gobj); \
}
#endif
#if GC_DEBUG_VERBOSE
void gc_mark_black(object obj)
{
// TODO: is sync required to get colors? probably not on the collector
// thread (at least) since colors are only changed once during the clear
// phase and before the first handshake.
int markColor = ck_pr_load_int(&gc_color_mark);
if (is_object_type(obj) && mark(obj) != markColor) {
// Gray any child objects
// Note we probably should use some form of atomics/synchronization
// for cons and vector types, as these pointers could change.
switch (type_of(obj)) {
case pair_tag:{
gc_collector_mark_gray(obj, car(obj));
gc_collector_mark_gray(obj, cdr(obj));
break;
}
case closure1_tag:
gc_collector_mark_gray(obj, ((closure1) obj)->element);
break;
case closureN_tag:{
int i, n = ((closureN) obj)->num_elements;
for (i = 0; i < n; i++) {
gc_collector_mark_gray(obj, ((closureN) obj)->elements[i]);
}
break;
}
case vector_tag:{
int i, n = ((vector) obj)->num_elements;
for (i = 0; i < n; i++) {
gc_collector_mark_gray(obj, ((vector) obj)->elements[i]);
}
break;
}
case cvar_tag:{
cvar_type *c = (cvar_type *) obj;
object pvar = *(c->pvar);
if (pvar) {
gc_collector_mark_gray(obj, pvar);
}
break;
}
default:
break;
}
if (mark(obj) != gc_color_red) {
// Only blacken objects on the heap
mark(obj) = markColor;
}
if (mark(obj) != gc_color_red) {
fprintf(stderr, "marked %p %d\n", obj, markColor);
} else {
fprintf(stderr, "not marking stack obj %p %d\n", obj, markColor);
}
}
}
#else
// See full version above for debugging purposes.
// Also sync any changes to this macro with the function version
#define gc_mark_black(obj) \
{ \
int markColor = ck_pr_load_int(&gc_color_mark); \
if (is_object_type(obj) && mark(obj) != markColor) { \
switch (type_of(obj)) { \
case pair_tag:{ \
gc_collector_mark_gray(obj, car(obj)); \
gc_collector_mark_gray(obj, cdr(obj)); \
break; \
} \
case closure1_tag: \
gc_collector_mark_gray(obj, ((closure1) obj)->element); \
break; \
case closureN_tag:{ \
int i, n = ((closureN) obj)->num_elements; \
for (i = 0; i < n; i++) { \
gc_collector_mark_gray(obj, ((closureN) obj)->elements[i]); \
} \
break; \
} \
case vector_tag:{ \
int i, n = ((vector) obj)->num_elements; \
for (i = 0; i < n; i++) { \
gc_collector_mark_gray(obj, ((vector) obj)->elements[i]); \
} \
break; \
} \
case cvar_tag:{ \
cvar_type *c = (cvar_type *) obj; \
object pvar = *(c->pvar); \
if (pvar) { \
gc_collector_mark_gray(obj, pvar); \
} \
break; \
} \
default: \
break; \
} \
if (mark(obj) != gc_color_red) { \
mark(obj) = markColor; \
} \
} \
}
#endif
/**
* @brief The collector's tracing algorithm
*
* This function ensures all live objects are marked prior to transitioning
* to the collector's sweep phase.
*/
void gc_collector_trace()
{
ck_array_iterator_t iterator;
gc_thread_data *m;
int clean = 0;
while (!clean) {
clean = 1;
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
// TODO: ideally, want to use a lock-free data structure to prevent
// having to use a mutex here. see corresponding code in gc_mark_gray
pthread_mutex_lock(&(m->lock));
while (m->last_read < m->last_write) {
clean = 0;
#if GC_DEBUG_VERBOSE
fprintf(stderr,
"gc_mark_black mark buffer %p, last_read = %d last_write = %d\n",
(m->mark_buffer)[m->last_read], m->last_read, m->last_write);
#endif
gc_mark_black((m->mark_buffer)[m->last_read]);
gc_empty_collector_stack();
(m->last_read)++; // Inc here to prevent off-by-one error
}
pthread_mutex_unlock(&(m->lock));
// Try checking the condition once more after giving the
// mutator a chance to respond, to prevent exiting early.
// This is experimental, not sure if it is necessary
if (clean) {
pthread_mutex_lock(&(m->lock));
if (m->last_read < m->last_write) {
#if GC_SAFETY_CHECKS
fprintf(stderr,
"gc_collector_trace - might have exited trace early\n");
#endif
clean = 0;
} else if (m->pending_writes) {
clean = 0;
}
pthread_mutex_unlock(&(m->lock));
}
}
}
}
/**
* @brief Empty the collector's mark stack
*
* Objects on the stack are removed one at a time and marked
*/
void gc_empty_collector_stack()
{
object obj;
// Mark stack is only used by the collector thread, so no sync needed
while (mark_stack_i > 0) { // not empty
mark_stack_i--;
//#if GC_DEBUG_VERBOSE
// fprintf(stderr, "gc_mark_black mark stack %p \n",
// mark_stack[mark_stack_i]);
//#endif
obj = mark_stack[mark_stack_i];
gc_mark_black(obj);
}
}
/**
* @brief Called by the collector thread to perform a handshake with
* all of the mutators
* @param s Transition to this GC status
*/
void gc_handshake(gc_status_type s)
{
gc_post_handshake(s);
gc_wait_handshake();
}
/**
* @brief Change GC status to the given type
* @param s Transition to this GC status
*/
void gc_post_handshake(gc_status_type s)
{
int status = ck_pr_load_int(&gc_status_col);
while (!ck_pr_cas_int(&gc_status_col, status, s)) {
}
}
/**
* @brief Wait for all mutators to handshake
*
* This function is always called by the collector. If a mutator
* is blocked and cannot handshake, the collector will cooperate
* on its behalf, including invoking a minor GC of the mutator's
* stack, so major GC can proceed.
*/
void gc_wait_handshake()
{
ck_array_iterator_t iterator;
gc_thread_data *m;
int statusm, statusc, thread_status, i, buf_len;
struct timespec tim;
tim.tv_sec = 0;
tim.tv_nsec = 1000000; // 1 millisecond
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
while (1) {
// TODO: use an atomic comparison
statusc = ck_pr_load_int(&gc_status_col);
statusm = ck_pr_load_int(&(m->gc_status));
if (statusc == statusm) {
// Handshake succeeded, check next mutator
break;
}
thread_status = ck_pr_load_int((int *)&(m->thread_state));
if (thread_status == CYC_THREAD_STATE_BLOCKED ||
thread_status == CYC_THREAD_STATE_BLOCKED_COOPERATING) {
if (statusm == STATUS_ASYNC) { // Prev state
ck_pr_cas_int(&(m->gc_status), statusm, statusc);
// Async is done, so clean up old mark data from the last collection
gc_zero_read_write_counts(m);
} else if (statusm == STATUS_SYNC1) {
ck_pr_cas_int(&(m->gc_status), statusm, statusc);
} else if (statusm == STATUS_SYNC2) {
//printf("DEBUG - is mutator still blocked?\n");
pthread_mutex_lock(&(m->lock));
// Check again, if thread is still blocked we need to cooperate
if (ck_pr_cas_int((int *)&(m->thread_state),
CYC_THREAD_STATE_BLOCKED,
CYC_THREAD_STATE_BLOCKED_COOPERATING)
||
ck_pr_cas_int((int *)&(m->thread_state),
CYC_THREAD_STATE_BLOCKED_COOPERATING,
CYC_THREAD_STATE_BLOCKED_COOPERATING)
) {
//printf("DEBUG - update mutator GC status\n");
ck_pr_cas_int(&(m->gc_status), statusm, statusc);
//printf("DEBUG - collector is cooperating for blocked mutator\n");
buf_len =
gc_minor(m, m->stack_limit, m->stack_start, m->gc_cont, NULL,
0);
// Handle any pending marks from write barrier
gc_sum_pending_writes(m, 1);
// Mark thread "roots", based on code from mutator's cooperator
gc_mark_gray(m, m->gc_cont);
//for (i = 0; i < m->gc_num_args; i++) {
// gc_mark_gray(m, m->gc_args[i]);
//}
if (m->scm_thread_obj) {
gc_mark_gray(m, m->scm_thread_obj);
}
if (m->exception_handler_stack) {
gc_mark_gray(m, m->exception_handler_stack);
}
if (m->param_objs) {
gc_mark_gray(m, m->param_objs);
}
// Also, mark everything the collector moved to the heap
for (i = 0; i < buf_len; i++) {
gc_mark_gray(m, m->moveBuf[i]);
}
m->gc_alloc_color = ck_pr_load_int(&gc_color_mark);
}
pthread_mutex_unlock(&(m->lock));
}
} else if (thread_status == CYC_THREAD_STATE_TERMINATED) {
// Thread is no longer running
break;
}
// At least for now, just give up quantum and come back to
// this quickly to test again. This probably could be more
// efficient.
nanosleep(&tim, NULL);
}
}
}
/////////////////////////////////////////////
// GC Collection cycle
void debug_dump_globals();
/**
* @brief Main collector function
*/
void gc_collector()
{
int old_clear, old_mark;
#if GC_DEBUG_TRACE
print_allocated_obj_counts();
print_current_time();
fprintf(stderr, " - Starting gc_collector\n");
#endif
//clear :
ck_pr_cas_int(&gc_stage, STAGE_RESTING, STAGE_CLEAR_OR_MARKING);
// exchange values of markColor and clearColor
old_clear = ck_pr_load_int(&gc_color_clear);
old_mark = ck_pr_load_int(&gc_color_mark);
while (!ck_pr_cas_int(&gc_color_clear, old_clear, old_mark)) {
}
while (!ck_pr_cas_int(&gc_color_mark, old_mark, old_clear)) {
}
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - swap clear %d / mark %d\n", gc_color_clear,
gc_color_mark);
#endif
gc_handshake(STATUS_SYNC1);
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - after handshake sync 1\n");
#endif
//mark :
gc_handshake(STATUS_SYNC2);
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - after handshake sync 2\n");
#endif
ck_pr_cas_int(&gc_stage, STAGE_CLEAR_OR_MARKING, STAGE_TRACING);
gc_post_handshake(STATUS_ASYNC);
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - after post_handshake async\n");
#endif
gc_request_mark_globals();
gc_wait_handshake();
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - after wait_handshake async\n");
#endif
//trace :
gc_collector_trace();
#if GC_DEBUG_TRACE
fprintf(stderr, "DEBUG - after trace\n");
//debug_dump_globals();
#endif
ck_pr_cas_int(&gc_stage, STAGE_TRACING, STAGE_SWEEPING);
//
//sweep :
gc_collector_sweep();
#if GC_DEBUG_TRACE
fprintf(stderr, "cleaning up any old thread data\n");
#endif
gc_free_old_thread_data();
// Idle the GC thread
ck_pr_cas_int(&gc_stage, STAGE_SWEEPING, STAGE_RESTING);
}
void *collector_main(void *arg)
{
int stage;
struct timespec tim;
#ifdef DEBUG_THREADS
pthread_t tid = pthread_self();
int sid = syscall(SYS_gettid);
printf("GC thread LWP id is %d\n", sid);
//printf("GC thread POSIX thread id is %d\n", tid);
#endif
tim.tv_sec = 0;
tim.tv_nsec = 100 * NANOSECONDS_PER_MILLISECOND;
while (1) {
stage = ck_pr_load_int(&gc_stage);
if (stage != STAGE_RESTING) {
gc_collector();
}
nanosleep(&tim, NULL);
}
return NULL;
}
/**
* @brief A high-resolution sleep function.
*
* @param ms Sleep time in milliseconds
*/
void gc_sleep_ms(int ms)
{
struct timespec tim;
tim.tv_sec = 0;
tim.tv_nsec = ms * NANOSECONDS_PER_MILLISECOND;
nanosleep(&tim, NULL);
}
static pthread_t collector_thread;
/**
* @brief Spawn the collector thread
*/
void gc_start_collector()
{
if (pthread_create
(&collector_thread, NULL, collector_main, &collector_thread)) {
fprintf(stderr, "Error creating collector thread\n");
exit(1);
}
}
/**
* @brief Mark globals as part of the tracing collector
* @param globals
* @param global_table
*
* This is called by the collector thread
*/
void gc_mark_globals(object globals, object global_table)
{
#if GC_DEBUG_TRACE
//fprintf(stderr, "(gc_mark_globals heap: %p size: %d)\n", h, (unsigned int)gc_heap_total_size(h));
fprintf(stderr, "Cyc_global_variables %p\n", globals);
#endif
// Mark global variables
gc_mark_black(globals); // Internal global used by the runtime
// Marking it ensures all glos are marked
{
list l = global_table;
for (; l != NULL; l = cdr(l)) {
cvar_type *c = (cvar_type *) car(l);
object glo = *(c->pvar);
if (glo != NULL) {
#if GC_DEBUG_VERBOSE
fprintf(stderr, "global pvar %p\n", glo);
#endif
gc_mark_black(glo); // Mark actual object the global points to
}
}
}
}
/////////////////////////////////////////////
// END tri-color marking section
/////////////////////////////////////////////
/**
* @brief Initialize runtime data structures for a thread.
* @param thd Mutator's thread data
* @param mut_num Unused
* @param stack_base Bottom of the mutator's stack
* @param stack_size Max allowed size of mutator's stack before triggering minor GC
*
* Must be called on the target thread itself during startup,
* to verify stack limits are setup correctly.
*/
void gc_thread_data_init(gc_thread_data * thd, int mut_num, char *stack_base,
long stack_size)
{
char stack_ref;
thd->stack_start = stack_base;
#if STACK_GROWTH_IS_DOWNWARD
thd->stack_limit = stack_base - stack_size;
#else
thd->stack_limit = stack_base + stack_size;
#endif
if (stack_overflow(stack_base, &stack_ref)) {
fprintf(stderr,
"Error: Stack is growing in the wrong direction! Rebuild with STACK_GROWTH_IS_DOWNWARD changed to %d\n",
(1 - STACK_GROWTH_IS_DOWNWARD));
exit(1);
}
thd->stack_traces = calloc(MAX_STACK_TRACES, sizeof(char *));
thd->stack_trace_idx = 0;
thd->stack_prev_frame = NULL;
thd->mutations = NULL;
thd->mutation_buflen = 128;
thd->mutation_count = 0;
thd->mutations =
vpbuffer_realloc(thd->mutations, &(thd->mutation_buflen));
thd->globals_changed = 1;
thd->param_objs = NULL;
thd->exception_handler_stack = NULL;
thd->scm_thread_obj = NULL;
thd->thread_state = CYC_THREAD_STATE_NEW;
//thd->mutator_num = mut_num;
thd->jmp_start = malloc(sizeof(jmp_buf));
thd->gc_args = malloc(sizeof(object) * NUM_GC_ARGS);
thd->gc_num_args = 0;
thd->moveBufLen = 0;
gc_thr_grow_move_buffer(thd);
thd->gc_alloc_color = ck_pr_load_int(&gc_color_clear);
thd->gc_status = ck_pr_load_int(&gc_status_col);
thd->pending_writes = 0;
thd->last_write = 0;
thd->last_read = 0;
thd->mark_buffer = NULL;
thd->mark_buffer_len = 128;
thd->mark_buffer =
vpbuffer_realloc(thd->mark_buffer, &(thd->mark_buffer_len));
if (pthread_mutex_init(&(thd->heap_lock), NULL) != 0) {
fprintf(stderr, "Unable to initialize thread mutex\n");
exit(1);
}
if (pthread_mutex_init(&(thd->lock), NULL) != 0) {
fprintf(stderr, "Unable to initialize thread mutex\n");
exit(1);
}
thd->cached_heap_free_sizes = calloc(5, sizeof(uintptr_t));
thd->cached_heap_total_sizes = calloc(5, sizeof(uintptr_t));
thd->heap = calloc(1, sizeof(gc_heap_root));
thd->heap->heap = calloc(1, sizeof(gc_heap *) * NUM_HEAP_TYPES);
thd->heap->heap[HEAP_REST] = gc_heap_create(HEAP_REST, INITIAL_HEAP_SIZE, 0, 0, thd);
thd->heap->heap[HEAP_SM] = gc_heap_create(HEAP_SM, INITIAL_HEAP_SIZE, 0, 0, thd);
thd->heap->heap[HEAP_64] = gc_heap_create(HEAP_64, INITIAL_HEAP_SIZE, 0, 0, thd);
if (sizeof(void *) == 8) { // Only use this heap on 64-bit platforms
thd->heap->heap[HEAP_96] = gc_heap_create(HEAP_96, INITIAL_HEAP_SIZE, 0, 0, thd);
}
thd->heap->heap[HEAP_HUGE] = gc_heap_create(HEAP_HUGE, 1024, 0, 0, thd);
}
/**
* @brief Free all data for the given mutator
* @param thd Mutator's thread data object containing data to free
*/
void gc_thread_data_free(gc_thread_data * thd)
{
if (thd) {
if (pthread_mutex_destroy(&thd->lock) != 0) {
// TODO: can only destroy the lock if it is unlocked. need to make sure we
// can guarantee that is the case prior to making this call
// On the other hand, can we just use sleep and a loop to retry??
fprintf(stderr, "Thread mutex is locked, unable to free\n");
exit(1);
}
if (pthread_mutex_destroy(&thd->heap_lock) != 0) {
fprintf(stderr, "Thread heap mutex is locked, unable to free\n");
exit(1);
}
// Merge heaps for the terminating thread into the main thread's heap.
// Eventually any data that is unused will be freed, but we need to
// keep the heap pages for now because they could still contain live
// objects.
// Lock the primordial thread (hopefully will not cause any deadlocks)
// but don't bother locking thd since it is already done by now.
pthread_mutex_lock(&(primordial_thread->heap_lock));
gc_merge_all_heaps(primordial_thread, thd);
pthread_mutex_unlock(&(primordial_thread->heap_lock));
if (thd->cached_heap_free_sizes)
free(thd->cached_heap_free_sizes);
if (thd->cached_heap_total_sizes)
free(thd->cached_heap_total_sizes);
if (thd->jmp_start)
free(thd->jmp_start);
if (thd->gc_args)
free(thd->gc_args);
if (thd->moveBuf)
free(thd->moveBuf);
if (thd->mark_buffer)
free(thd->mark_buffer);
if (thd->stack_traces)
free(thd->stack_traces);
if (thd->mutations) {
free(thd->mutations);
}
free(thd);
}
}
/**
* @brief Merge one heap into another.
* @param hdest Heap that will receive new pages
* @param hsrc Heap that is being merged to the end of `hdest`
*
* This function assumes appropriate locks are already held.
*/
void gc_heap_merge(gc_heap *hdest, gc_heap *hsrc)
{
gc_heap *last = gc_heap_last(hdest);
last->next = hsrc;
}
/**
* @brief Merge all thread heaps into another.
* @param dest Heap receiving new pages
* @param src Heap containing pages to be appended
*
* Assumes appropriate locks are already held.
*/
void gc_merge_all_heaps(gc_thread_data *dest, gc_thread_data *src)
{
gc_heap *hdest, *hsrc;
int heap_type;
for (heap_type = 0; heap_type < NUM_HEAP_TYPES; heap_type++) {
hdest = dest->heap->heap[heap_type];
hsrc = src->heap->heap[heap_type];
if (hdest && hsrc) {
gc_heap_merge(hdest, hsrc);
ck_pr_add_ptr(&(dest->cached_heap_total_sizes[heap_type]),
ck_pr_load_ptr(&(src->cached_heap_total_sizes[heap_type])));
ck_pr_add_ptr(&(dest->cached_heap_free_sizes[heap_type]),
ck_pr_load_ptr(&(src->cached_heap_free_sizes[heap_type])));
}
}
ck_pr_add_int(&(dest->heap_num_huge_allocations),
ck_pr_load_int(&(src->heap_num_huge_allocations)));
#ifdef GC_DEBUG_TRACE
fprintf(stderr, "Finished merging old heap data\n");
#endif
}
/**
* @brief Called explicitly from a mutator thread to let the collector know
* it (may) block for an unknown period of time.
* @param thd Mutator's thread data
* @param cont The mutator's current continuation. This is required so that we can trace over this object in case the collector has to cooperate for the mutator.
*/
void gc_mutator_thread_blocked(gc_thread_data * thd, object cont)
{
thd->gc_cont = cont;
thd->gc_num_args = 0; // Will be set later, after collection
if (!ck_pr_cas_int((int *)&(thd->thread_state),
CYC_THREAD_STATE_RUNNABLE, CYC_THREAD_STATE_BLOCKED)) {
fprintf(stderr,
"Unable to change thread from runnable to blocked. status = %d\n",
thd->thread_state);
exit(1);
}
}
void Cyc_apply_from_buf(void *data, int argc, object prim, object * buf);
/**
* @brief Called explicitly from a mutator thread to let the collector know
* that it has finished blocking.
* @param thd Mutator's thread data
* @param result Data returned by the blocking function
*
* In addition, if the collector cooperated on behalf of the mutator while
* it was blocking, the mutator will move any remaining stack objects to
* the heap and longjmp.
*/
void gc_mutator_thread_runnable(gc_thread_data * thd, object result)
{
char stack_limit;
// Transition from blocked back to runnable using CAS.
// If we are unable to transition back, assume collector
// has cooperated on behalf of this mutator thread.
if (!ck_pr_cas_int((int *)&(thd->thread_state),
CYC_THREAD_STATE_BLOCKED, CYC_THREAD_STATE_RUNNABLE)) {
//printf("DEBUG - Collector cooperated, wait for it to finish. status is %d\n", thd->thread_state);
// wait for the collector to finish
pthread_mutex_lock(&(thd->lock));
pthread_mutex_unlock(&(thd->lock));
// update thread status
while (!ck_pr_cas_int((int *)&(thd->thread_state),
CYC_THREAD_STATE_BLOCKED_COOPERATING,
CYC_THREAD_STATE_RUNNABLE)) {
}
// Setup value to send to continuation
thd->gc_args[0] = result;
thd->gc_num_args = 1;
// Move any remaining stack objects (should only be the result?) to heap
gc_minor(thd, &stack_limit, thd->stack_start, thd->gc_cont, thd->gc_args,
thd->gc_num_args);
// Handle any pending marks from write barrier
gc_sum_pending_writes(thd, 0);
//printf("DEBUG - Call into gc_cont after collector coop\n");
// Whoa.
longjmp(*(thd->jmp_start), 1);
} else {
// Collector didn't do anything; make a normal continuation call
if (type_of(thd->gc_cont) == pair_tag || prim(thd->gc_cont)) {
thd->gc_args[0] = result;
Cyc_apply_from_buf(thd, 1, thd->gc_cont, thd->gc_args);
} else {
(((closure) (thd->gc_cont))->fn) (thd, 1, thd->gc_cont, result);
}
}
}
//// Unit testing:
//int main(int argc, char **argv) {
// int a = 1, b = 2, c = 3, i;
// void **buf = NULL;
// int size = 1;
//
// buf = vpbuffer_realloc(buf, &size);
// printf("buf = %p, size = %d\n", buf, size);
// buf = vpbuffer_add(buf, &size, 0, &a);
// printf("buf = %p, size = %d\n", buf, size);
// buf = vpbuffer_add(buf, &size, 1, &b);
// printf("buf = %p, size = %d\n", buf, size);
// buf = vpbuffer_add(buf, &size, 2, &c);
// printf("buf = %p, size = %d\n", buf, size);
// buf = vpbuffer_add(buf, &size, 3, &a);
// printf("buf = %p, size = %d\n", buf, size);
// buf = vpbuffer_add(buf, &size, 4, &b);
// printf("buf = %p, size = %d\n", buf, size);
// for (i = 5; i < 20; i++) {
// buf = vpbuffer_add(buf, &size, i, &c);
// }
//
// for (i = 0; i < 20; i++){
// printf("%d\n", *((int *) buf[i]));
// }
// vpbuffer_free(buf);
// printf("buf = %p, size = %d\n", buf, size);
// return 0;
//}
//
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