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/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1993 by Xerox Corporation. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to copy this garbage collector for any purpose,
* provided the above notices are retained on all copies.
*
*/
# include <stdio.h>
# include <signal.h>
# include <sys/types.h>
# include "gc_private.h"
/*
* Separate free lists are maintained for different sized objects
* up to MAXOBJSZ.
* The call GC_allocobj(i,k) ensures that the freelist for
* kind k objects of size i points to a non-empty
* free list. It returns a pointer to the first entry on the free list.
* In a single-threaded world, GC_allocobj may be called to allocate
* an object of (small) size i as follows:
*
* opp = &(GC_objfreelist[i]);
* if (*opp == 0) GC_allocobj(i, NORMAL);
* ptr = *opp;
* *opp = obj_link(ptr);
*
* Note that this is very fast if the free list is non-empty; it should
* only involve the execution of 4 or 5 simple instructions.
* All composite objects on freelists are cleared, except for
* their first word.
*/
/*
* The allocator uses GC_allochblk to allocate large chunks of objects.
* These chunks all start on addresses which are multiples of
* HBLKSZ. Each allocated chunk has an associated header,
* which can be located quickly based on the address of the chunk.
* (See headers.c for details.)
* This makes it possible to check quickly whether an
* arbitrary address corresponds to an object administered by the
* allocator.
*/
word GC_non_gc_bytes = 0; /* Number of bytes not intended to be collected */
word GC_gc_no = 0;
int GC_incremental = 0; /* By default, stop the world. */
int GC_full_freq = 3; /* Every 4th collection is a full */
/* collection. */
char * GC_copyright[] =
{"Copyright 1988,1989 Hans-J. Boehm and Alan J. Demers",
"Copyright (c) 1991-1993 by Xerox Corporation. All rights reserved.",
"THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY",
" EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK."};
/* some more variables */
extern signed_word GC_mem_found; /* Number of reclaimed longwords */
/* after garbage collection */
bool GC_dont_expand = 0;
word GC_free_space_divisor = 4;
/* Return the minimum number of words that must be allocated between */
/* collections to amortize the collection cost. */
static word min_words_allocd()
{
int dummy;
# ifdef THREADS
/* We punt, for now. */
register signed_word stack_size = 10000;
# else
register signed_word stack_size = (ptr_t)(&dummy) - GC_stackbottom;
# endif
register word total_root_size; /* includes double stack size, */
/* since the stack is expensive */
/* to scan. */
if (stack_size < 0) stack_size = -stack_size;
total_root_size = 2 * stack_size + GC_root_size;
if (GC_incremental) {
return(BYTES_TO_WORDS(GC_heapsize + total_root_size)
/ (2 * GC_free_space_divisor));
} else {
return(BYTES_TO_WORDS(GC_heapsize + total_root_size)
/ GC_free_space_divisor);
}
}
/* Return the number of words allocated, adjusted for explicit storage */
/* management, etc.. This number is used in deciding when to trigger */
/* collections. */
word GC_adj_words_allocd()
{
register signed_word result;
register signed_word expl_managed =
BYTES_TO_WORDS((long)GC_non_gc_bytes
- (long)GC_non_gc_bytes_at_gc);
/* Don't count what was explicitly freed, or newly allocated for */
/* explicit management. Note that deallocating an explicitly */
/* managed object should not alter result, assuming the client */
/* is playing by the rules. */
result = (signed_word)GC_words_allocd
- (signed_word)GC_mem_freed - expl_managed;
if (result > (signed_word)GC_words_allocd) result = GC_words_allocd;
/* probably client bug or unfortunate scheduling */
result += GC_words_wasted;
/* This doesn't reflect useful work. But if there is lots of */
/* new fragmentation, the same is probably true of the heap, */
/* and the collection will be correspondingly cheaper. */
if (result < (signed_word)(GC_words_allocd >> 2)) {
/* Always count at least 1/8 of the allocations. We don't want */
/* to collect too infrequently, since that would inhibit */
/* coalescing of free storage blocks. */
/* This also makes us partially robust against client bugs. */
return(GC_words_allocd >> 3);
} else {
return(result);
}
}
/* Clear up a few frames worth og garbage left at the top of the stack. */
/* This is used to prevent us from accidentally treating garbade left */
/* on the stack by other parts of the collector as roots. This */
/* differs from the code in misc.c, which actually tries to keep the */
/* stack clear of long-lived, client-generated garbage. */
void GC_clear_a_few_frames()
{
# define NWORDS 64
word frames[NWORDS];
register int i;
for (i = 0; i < NWORDS; i++) frames[i] = 0;
}
/* Have we allocated enough to amortize a collection? */
bool GC_should_collect()
{
return(GC_adj_words_allocd() >= min_words_allocd());
}
/*
* Initiate a garbage collection if appropriate.
* Choose judiciously
* between partial, full, and stop-world collections.
* Assumes lock held, signals disabled.
*/
void GC_maybe_gc()
{
static int n_partial_gcs = 0;
if (GC_should_collect()) {
if (!GC_incremental) {
GC_gcollect_inner();
n_partial_gcs = 0;
} else if (n_partial_gcs >= GC_full_freq) {
GC_initiate_full();
n_partial_gcs = 0;
} else {
GC_initiate_partial(GC_gc_no+1);
n_partial_gcs++;
}
}
}
/*
* Stop the world garbage collection. Assumes lock held, signals disabled.
*/
bool GC_gcollect_inner()
{
# ifdef PRINTSTATS
GC_printf2(
"Initiating full world-stop collection %lu after %ld allocd bytes\n",
(unsigned long) GC_gc_no+1,
(long)WORDS_TO_BYTES(GC_words_allocd));
# endif
GC_promote_black_lists();
/* GC_reclaim_or_delete_all(); -- not needed: no intervening allocation */
GC_clear_marks();
STOP_WORLD();
GC_stopped_mark();
START_WORLD();
GC_finish_collection();
}
/*
* Perform n units of garbage collection work. A unit is intended to touch
* roughly a GC_RATE pages. Every once in a while, we do more than that.
*/
# define GC_RATE 8
void GC_collect_a_little(n)
int n;
{
register int i;
if (GC_collection_in_progress()) {
for (i = 0; i < GC_RATE*n; i++) {
if (GC_mark_some()) {
/* Need to finish a collection */
STOP_WORLD();
GC_stopped_mark();
START_WORLD();
GC_finish_collection();
break;
}
}
} else {
GC_maybe_gc();
}
}
/*
* World-stopped mark phase. Assumes lock is held, signals are disabled,
* and the world is stopped.
*/
void GC_stopped_mark()
{
# ifdef PRINTTIMES
CLOCK_TYPE start_time;
CLOCK_TYPE done_time;
GET_TIME(start_time);
# endif
# ifdef PRINTSTATS
GC_printf2("Collection %lu reclaimed %ld bytes\n",
(unsigned long) GC_gc_no,
(long)WORDS_TO_BYTES(GC_mem_found));
# endif
GC_gc_no++;
# ifdef PRINTSTATS
GC_printf3(
"--> Collection number %lu after %lu allocated + %lu wasted bytes\n",
(unsigned long) GC_gc_no,
(unsigned long) WORDS_TO_BYTES(GC_words_allocd),
(unsigned long) WORDS_TO_BYTES(GC_words_wasted));
GC_printf1("---> heapsize = %lu bytes\n",
(unsigned long) GC_heapsize);
/* Printf arguments may be pushed in funny places. Clear the */
/* space. */
GC_printf0("");
# endif
/* Mark from all roots. */
/* Minimize junk left in my registers and on the stack */
GC_clear_a_few_frames();
GC_noop(0,0,0,0,0,0);
GC_initiate_partial(GC_gc_no);
while(!GC_mark_some());
/* Check all debugged objects for consistency */
if (GC_debugging_started) {
(*GC_check_heap)();
}
# ifdef PRINTTIMES
GET_TIME(done_time);
GC_printf1("World-stopped marking took %lu msecs\n",
MS_TIME_DIFF(done_time,start_time));
# endif
}
/* Finish up a collection. Assumes lock is held, signals are disabled, */
/* but the world is otherwise running. */
void GC_finish_collection()
{
# ifdef PRINTTIMES
CLOCK_TYPE start_time;
CLOCK_TYPE finalize_time;
CLOCK_TYPE done_time;
GET_TIME(start_time);
finalize_time = start_time;
# endif
# ifdef GATHERSTATS
GC_mem_found = 0;
# endif
# ifdef FIND_LEAK
/* Mark all objects on the free list. All objects should be */
/* marked when we're done. */
{
register word size; /* current object size */
register ptr_t p; /* pointer to current object */
register struct hblk * h; /* pointer to block containing *p */
register hdr * hhdr;
register int word_no; /* "index" of *p in *q */
int kind;
for (kind = 0; kind < GC_n_kinds; kind++) {
for (size = 1; size <= MAXOBJSZ; size++) {
for (p= GC_obj_kinds[kind].ok_freelist[size];
p != 0; p=obj_link(p)){
h = HBLKPTR(p);
hhdr = HDR(h);
word_no = (((word *)p) - ((word *)h));
set_mark_bit_from_hdr(hhdr, word_no);
}
}
}
}
/* Check that everything is marked */
GC_start_reclaim(TRUE);
# else
GC_finalize();
# ifdef STUBBORN_ALLOC
GC_clean_changing_list();
# endif
# ifdef PRINTTIMES
GET_TIME(finalize_time);
# endif
/* Clear free list mark bits, in case they got accidentally marked */
/* Note: HBLKPTR(p) == pointer to head of block containing *p */
/* Also subtract memory remaining from GC_mem_found count. */
/* Note that composite objects on free list are cleared. */
/* Thus accidentally marking a free list is not a problem; only */
/* objects on the list itself will be marked, and that's fixed here. */
{
register word size; /* current object size */
register ptr_t p; /* pointer to current object */
register struct hblk * h; /* pointer to block containing *p */
register hdr * hhdr;
register int word_no; /* "index" of *p in *q */
int kind;
for (kind = 0; kind < GC_n_kinds; kind++) {
for (size = 1; size <= MAXOBJSZ; size++) {
for (p= GC_obj_kinds[kind].ok_freelist[size];
p != 0; p=obj_link(p)){
h = HBLKPTR(p);
hhdr = HDR(h);
word_no = (((word *)p) - ((word *)h));
clear_mark_bit_from_hdr(hhdr, word_no);
GC_mem_found -= size;
}
}
}
}
# ifdef PRINTSTATS
GC_printf1("Bytes recovered before sweep - f.l. count = %ld\n",
(long)WORDS_TO_BYTES(GC_mem_found));
# endif
/* Reconstruct free lists to contain everything not marked */
GC_start_reclaim(FALSE);
# endif /* !FIND_LEAK */
# ifdef PRINTSTATS
GC_printf2(
"Immediately reclaimed %ld bytes in heap of size %lu bytes\n",
(long)WORDS_TO_BYTES(GC_mem_found),
(unsigned long)GC_heapsize);
GC_printf2("%lu (atomic) + %lu (composite) bytes in use\n",
(unsigned long)WORDS_TO_BYTES(GC_atomic_in_use),
(unsigned long)WORDS_TO_BYTES(GC_composite_in_use));
# endif
/* Reset or increment counters for next cycle */
GC_words_allocd_before_gc += GC_words_allocd;
GC_non_gc_bytes_at_gc = GC_non_gc_bytes;
GC_words_allocd = 0;
GC_words_wasted = 0;
GC_mem_freed = 0;
# ifdef PRINTTIMES
GET_TIME(done_time);
GC_printf2("Finalize + initiate sweep took %lu + %lu msecs\n",
MS_TIME_DIFF(finalize_time,start_time),
MS_TIME_DIFF(done_time,finalize_time));
# endif
}
/* Externally callable routine to invoke full, stop-world collection */
void GC_gcollect()
{
DCL_LOCK_STATE;
DISABLE_SIGNALS();
LOCK();
if (!GC_is_initialized) GC_init_inner();
/* Minimize junk left in my registers */
GC_noop(0,0,0,0,0,0);
(void) GC_gcollect_inner();
UNLOCK();
ENABLE_SIGNALS();
}
word GC_n_heap_sects = 0; /* Number of sections currently in heap. */
/*
* Use the chunk of memory starting at p of syze bytes as part of the heap.
* Assumes p is HBLKSIZE aligned, and bytes is a multiple of HBLKSIZE.
*/
void GC_add_to_heap(p, bytes)
struct hblk *p;
word bytes;
{
word words;
if (GC_n_heap_sects >= MAX_HEAP_SECTS) {
GC_err_printf0(
"Too many heap sections: Increase MAXHINCR or MAX_HEAP_SECTS");
ABORT("Too many heap sections: Increase MAXHINCR or MAX_HEAP_SECTS");
}
if (!GC_install_header(p)) {
/* This is extremely unlikely. Can't add it. This will */
/* almost certainly result in a 0 return from the allocator, */
/* which is entirely appropriate. */
return;
}
GC_heap_sects[GC_n_heap_sects].hs_start = (ptr_t)p;
GC_heap_sects[GC_n_heap_sects].hs_bytes = bytes;
GC_n_heap_sects++;
words = BYTES_TO_WORDS(bytes - HDR_BYTES);
HDR(p) -> hb_sz = words;
GC_freehblk(p);
GC_heapsize += bytes;
if ((ptr_t)p <= GC_least_plausible_heap_addr
|| GC_least_plausible_heap_addr == 0) {
GC_least_plausible_heap_addr = (ptr_t)p - sizeof(word);
/* Making it a little smaller than necessary prevents */
/* us from getting a false hit from the variable */
/* itself. There's some unintentional reflection */
/* here. */
}
if ((ptr_t)p + bytes >= GC_greatest_plausible_heap_addr) {
GC_greatest_plausible_heap_addr = (ptr_t)p + bytes;
}
}
ptr_t GC_least_plausible_heap_addr = (ptr_t)ONES;
ptr_t GC_greatest_plausible_heap_addr = 0;
ptr_t GC_max(x,y)
ptr_t x, y;
{
return(x > y? x : y);
}
ptr_t GC_min(x,y)
ptr_t x, y;
{
return(x < y? x : y);
}
/*
* this explicitly increases the size of the heap. It is used
* internally, but my also be invoked from GC_expand_hp by the user.
* The argument is in units of HBLKSIZE.
* Returns FALSE on failure.
*/
bool GC_expand_hp_inner(n)
word n;
{
word bytes = n * HBLKSIZE;
struct hblk * space = GET_MEM(bytes);
word expansion_slop; /* Number of bytes by which we expect the */
/* heap to expand soon. */
if (n > 2*GC_hincr) {
GC_hincr = n/2;
}
if( space == 0 ) {
return(FALSE);
}
# ifdef PRINTSTATS
GC_printf2("Increasing heap size by %lu after %lu allocated bytes\n",
(unsigned long)bytes,
(unsigned long)WORDS_TO_BYTES(GC_words_allocd));
# endif
expansion_slop = 8 * WORDS_TO_BYTES(min_words_allocd());
if (5 * HBLKSIZE * MAXHINCR > expansion_slop) {
expansion_slop = 5 * HBLKSIZE * MAXHINCR;
}
if (GC_last_heap_addr == 0 && !((word)space & SIGNB)
|| GC_last_heap_addr != 0 && GC_last_heap_addr < (ptr_t)space) {
/* Assume the heap is growing up */
GC_greatest_plausible_heap_addr =
GC_max(GC_greatest_plausible_heap_addr,
(ptr_t)space + bytes + expansion_slop);
} else {
/* Heap is growing down */
GC_least_plausible_heap_addr =
GC_min(GC_least_plausible_heap_addr,
(ptr_t)space - expansion_slop);
}
GC_prev_heap_addr = GC_last_heap_addr;
GC_last_heap_addr = (ptr_t)space;
GC_add_to_heap(space, bytes);
return(TRUE);
}
/* Really returns a bool, but it's externally visible, so that's clumsy. */
int GC_expand_hp(n)
int n;
{
int result;
DCL_LOCK_STATE;
DISABLE_SIGNALS();
LOCK();
if (!GC_is_initialized) GC_init_inner();
result = (int)GC_expand_hp_inner((word)n);
UNLOCK();
ENABLE_SIGNALS();
return(result);
}
bool GC_collect_or_expand(needed_blocks)
word needed_blocks;
{
static int count = 0; /* How many failures? */
if (!GC_incremental && !GC_dont_gc && GC_should_collect()) {
GC_gcollect_inner();
} else {
if (!GC_expand_hp_inner(GC_hincr + needed_blocks)
&& !GC_expand_hp_inner(needed_blocks)) {
if (count++ < 20) {
WARN("Out of Memory! Trying to continue ...\n");
GC_gcollect_inner();
} else {
WARN("Out of Memory! Returning NIL!\n");
return(FALSE);
}
}
update_GC_hincr;
}
return(TRUE);
}
/*
* Make sure the object free list for sz is not empty.
* Return a pointer to the first object on the free list.
* The object MUST BE REMOVED FROM THE FREE LIST BY THE CALLER.
* Assumes we hold the allocator lock and signals are disabled.
*
*/
ptr_t GC_allocobj(sz, kind)
word sz;
int kind;
{
register ptr_t * flh = &(GC_obj_kinds[kind].ok_freelist[sz]);
if (sz == 0) return(0);
while (*flh == 0) {
/* Do our share of marking work */
if(GC_incremental && !GC_dont_gc) GC_collect_a_little(1);
/* Sweep blocks for objects of this size */
GC_continue_reclaim(sz, kind);
if (*flh == 0) {
GC_new_hblk(sz, kind);
}
if (*flh == 0) {
if (!GC_collect_or_expand((word)1)) return(0);
}
}
return(*flh);
}
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