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fd348ec43f
php-src/Zend/zend_gc.c
Dmitry Stogov fd348ec43f GC improvement
2018-03-01 03:17:21 +03:00

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/*
+----------------------------------------------------------------------+
| Zend Engine |
+----------------------------------------------------------------------+
| Copyright (c) 1998-2018 Zend Technologies Ltd. (http://www.zend.com) |
+----------------------------------------------------------------------+
| This source file is subject to version 2.00 of the Zend license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.zend.com/license/2_00.txt. |
| If you did not receive a copy of the Zend license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@zend.com so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: David Wang <planetbeing@gmail.com> |
| Dmitry Stogov <dmitry@zend.com> |
+----------------------------------------------------------------------+
*/
/* $Id$ */
/**
* zend_gc_collect_cycles
* ======================
*
* Colors and its meaning
* ----------------------
*
* BLACK (GC_BLACK) - In use or free.
* GREY (GC_GREY) - Possible member of cycle.
* WHITE (GC_WHITE) - Member of garbage cycle.
* PURPLE (GC_PURPLE) - Possible root of cycle.
*
* Colors described in the paper but not used
* ------------------------------------------
*
* GREEN - Acyclic
* RED - Candidate cycle underogin
* ORANGE - Candidate cycle awaiting epoch boundary.
*
*
* Flow
* =====
*
* The garbage collect cycle starts from 'gc_mark_roots', which traverses the
* possible roots, and calls mark_grey for roots are marked purple with
* depth-first traverse.
*
* After all possible roots are traversed and marked,
* gc_scan_roots will be called, and each root will be called with
* gc_scan(root->ref)
*
* gc_scan checkes the colors of possible members.
*
* If the node is marked as grey and the refcount > 0
* gc_scan_black will be called on that node to scan it's subgraph.
* otherwise (refcount == 0), it marks the node white.
*
* A node MAY be added to possbile roots when ZEND_UNSET_VAR happens or
* zend_assign_to_variable is called only when possible garbage node is
* produced.
* gc_possible_root() will be called to add the nodes to possible roots.
*
*
* For objects, we call their get_gc handler (by default 'zend_std_get_gc') to
* get the object properties to scan.
*
*
* @see http://researcher.watson.ibm.com/researcher/files/us-bacon/Bacon01Concurrent.pdf
*/
#include "zend.h"
#include "zend_API.h"
#ifndef GC_BENCH
# define GC_BENCH 0
#endif
#ifndef ZEND_GC_DEBUG
# define ZEND_GC_DEBUG 0
#endif
/* GC_TYPE */
#define GC_COLOR 0x300000
#define GC_BLACK 0x000000 /* must be zero */
#define GC_WHITE 0x100000
#define GC_GREY 0x200000
#define GC_PURPLE 0x300000
#define GC_ADDRESS(v) \
((v) & ~GC_COLOR)
#define GC_INFO_GET_COLOR(v) \
(((zend_uintptr_t)(v)) & GC_COLOR)
/* GC_TYPE_INFO */
#define GC_REF_SET_INFO(ref, info) \
gc_ref_set_info(ref, info)
#define GC_REF_SET_INFO_EX(ref, buffer, color) \
gc_ref_set_info_ex(ref, buffer, color)
#define GC_REF_GET_COLOR(ref) \
GC_INFO_GET_COLOR(GC_INFO(ref))
#define GC_REF_SET_COLOR(ref, c) do { \
GC_TYPE_INFO(ref) = ((c) << GC_INFO_SHIFT) | \
(GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK | ~(GC_COLOR << GC_INFO_SHIFT))); \
} while (0)
#define GC_REF_SET_BLACK(ref) do { \
GC_TYPE_INFO(ref) &= ~(GC_COLOR << GC_INFO_SHIFT); \
} while (0)
#define GC_REF_SET_PURPLE(ref) do { \
GC_TYPE_INFO(ref) |= (GC_COLOR << GC_INFO_SHIFT); \
} while (0)
/* GC buffer size */
#define GC_INVALID 0
#define GC_FIRST_REAL_ROOT 1
#define GC_DEFAULT_THRESHOLD 10000
#define GC_DEFAULT_BUF_SIZE (16 * 1024)
#define GC_BUF_GROW_STEP (128 * 1024)
#define GC_COMPRESS_FACTOR 4096 /* shold be 0 to disable compression */
#define GC_MAX_UNCOMPRESSED ((1024 * 1024) - GC_COMPRESS_FACTOR)
#define GC_MAX_BUF_SIZE (GC_COMPRESS_FACTOR ? (0x40000000) : GC_MAX_UNCOMPRESSED)
#define GC_NEED_COMPRESSION(addr) \
((GC_COMPRESS_FACTOR > 0) && (addr >= GC_MAX_UNCOMPRESSED))
/* GC flags */
#define GC_HAS_DESTRUCTORS (1<<0)
/* bit stealing tags for gc_root_buffer.ref */
#define GC_BITS 0x3
#define GC_ROOT 0x0 /* poissible root of circular garbage */
#define GC_UNUSED 0x1 /* part of linked list of unused buffers */
#define GC_GARBAGE 0x2 /* garbage to delete */
#define GC_GET_PTR(ptr) \
((void*)(((uintptr_t)(ptr)) & ~GC_BITS))
#define GC_IS_ROOT(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_ROOT)
#define GC_IS_UNUSED(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_UNUSED)
#define GC_IS_GARBAGE(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_GARBAGE)
#define GC_MAKE_GARBAGE(ptr) \
((void*)(((uintptr_t)(ptr)) | GC_GARBAGE))
/* unused buffers */
#define GC_HAS_UNUSED() \
(GC_G(unused) != GC_INVALID)
#define GC_FETCH_UNUSED() \
gc_fetch_unused()
#define GC_LINK_UNUSED(root) \
gc_link_unused(root)
#define GC_HAS_NEXT_UNUSED_UNDER_THRESHOLD() \
(GC_G(first_unused) < GC_G(gc_threshold))
#define GC_HAS_NEXT_UNUSED() \
(GC_G(first_unused) != GC_G(buf_size))
#define GC_FETCH_NEXT_UNUSED() \
gc_fetch_next_unused()
ZEND_API int (*gc_collect_cycles)(void);
typedef struct _gc_root_buffer {
zend_refcounted *ref;
} gc_root_buffer;
typedef struct _zend_gc_globals {
zend_bool gc_enabled;
zend_bool gc_active; /* GC currently running, forbid nested GC */
zend_bool gc_protected; /* GC protected, forbid root additions */
zend_bool gc_full;
gc_root_buffer *buf; /* preallocated arrays of buffers */
uint32_t buf_size; /* size of the GC buffer */
uint32_t gc_threshold; /* GC collection threshold */
uint32_t unused; /* linked list of unused buffers */
uint32_t first_unused; /* first unused buffer */
uint32_t num_roots; /* number of roots in GC buffer */
uint32_t gc_runs;
uint32_t collected;
#if GC_BENCH
uint32_t root_buf_length;
uint32_t root_buf_peak;
uint32_t zval_possible_root;
uint32_t zval_buffered;
uint32_t zval_remove_from_buffer;
uint32_t zval_marked_grey;
#endif
} zend_gc_globals;
#ifdef ZTS
static int gc_globals_id;
#define GC_G(v) ZEND_TSRMG(gc_globals_id, zend_gc_globals *, v)
#else
#define GC_G(v) (gc_globals.v)
static zend_gc_globals gc_globals;
#endif
#if GC_BENCH
# define GC_BENCH_INC(counter) GC_G(counter)++
# define GC_BENCH_DEC(counter) GC_G(counter)--
# define GC_BENCH_PEAK(peak, counter) do { \
if (GC_G(counter) > GC_G(peak)) { \
GC_G(peak) = GC_G(counter); \
} \
} while (0)
#else
# define GC_BENCH_INC(counter)
# define GC_BENCH_DEC(counter)
# define GC_BENCH_PEAK(peak, counter)
#endif
#if ZEND_GC_DEBUG > 1
# define GC_TRACE(format, ...) fprintf(stderr, format "\n", ##__VA_ARGS__);
# define GC_TRACE_REF(ref, format, ...) \
do { \
gc_trace_ref((zend_refcounted *) ref); \
fprintf(stderr, format "\n", ##__VA_ARGS__); \
} while (0)
# define GC_TRACE_SET_COLOR(ref, color) \
GC_TRACE_REF(ref, "->%s", gc_color_name(color))
#else
# define GC_TRACE_REF(ref, format, ...)
# define GC_TRACE_SET_COLOR(ref, new_color)
# define GC_TRACE(str)
#endif
static zend_always_inline uint32_t gc_compress(uint32_t idx)
{
ZEND_ASSERT(GC_NEED_COMPRESSION(idx));
return GC_MAX_UNCOMPRESSED + ((idx - GC_MAX_UNCOMPRESSED) % GC_COMPRESS_FACTOR);
}
static zend_always_inline uint32_t gc_decompress(zend_refcounted *ref, uint32_t idx)
{
ZEND_ASSERT(GC_NEED_COMPRESSION(idx));
while (idx < GC_G(first_unused)) {
gc_root_buffer *root = GC_G(buf) + idx;
if (root->ref == ref) {
return idx;
}
idx += GC_COMPRESS_FACTOR;
}
ZEND_ASSERT(0);
}
static zend_always_inline gc_root_buffer* gc_fetch_unused(void)
{
gc_root_buffer *root;
ZEND_ASSERT(GC_HAS_UNUSED());
root = (gc_root_buffer*)((char*)GC_G(buf) + GC_G(unused));
ZEND_ASSERT(GC_IS_UNUSED(root->ref));
GC_G(unused) = (uint32_t)(uintptr_t)GC_GET_PTR(root->ref);
return root;
}
static zend_always_inline void gc_link_unused(gc_root_buffer *root)
{
root->ref = (void*)(uintptr_t)(GC_G(unused) | GC_UNUSED);
GC_G(unused) = (char*)root - (char*)GC_G(buf);
}
static zend_always_inline gc_root_buffer* gc_fetch_next_unused(void)
{
gc_root_buffer *root;
ZEND_ASSERT(GC_HAS_NEXT_UNUSED());
root = GC_G(buf) + GC_G(first_unused);
GC_G(first_unused)++;
return root;
}
static zend_always_inline void gc_ref_set_info(zend_refcounted *ref, uint32_t info)
{
GC_TYPE_INFO(ref) = (info << GC_INFO_SHIFT)
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
}
static zend_always_inline void gc_ref_set_info_ex(zend_refcounted *ref, gc_root_buffer *buffer, uint32_t color)
{
if (GC_COMPRESS_FACTOR) {
uint32_t addr = buffer - GC_G(buf);
if (GC_NEED_COMPRESSION(addr)) {
addr = gc_compress(addr);
}
GC_TYPE_INFO(ref) = (addr << GC_INFO_SHIFT)
| (color << GC_INFO_SHIFT)
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
} else if (sizeof(gc_root_buffer) == 4) {
GC_TYPE_INFO(ref) =
(((char*)buffer + ((color) << 2) - (char*)GC_G(buf)) << (GC_INFO_SHIFT - 2))
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
} else if (sizeof(gc_root_buffer) == 8) {
GC_TYPE_INFO(ref) =
(((char*)buffer + ((color) << 3) - (char*)GC_G(buf)) << (GC_INFO_SHIFT - 3))
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
} else if (sizeof(gc_root_buffer) == 16) {
GC_TYPE_INFO(ref) =
(((char*)buffer + ((color) << 4) - (char*)GC_G(buf)) << (GC_INFO_SHIFT - 4))
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
} else if (sizeof(gc_root_buffer) == 32) {
GC_TYPE_INFO(ref) =
(((char*)buffer + ((color) << 5) - (char*)GC_G(buf)) << (GC_INFO_SHIFT - 5))
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
} else {
GC_TYPE_INFO(ref) = ((buffer - GC_G(buf)) << GC_INFO_SHIFT)
| (color << GC_INFO_SHIFT)
| (GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK));
}
}
#if ZEND_GC_DEBUG > 1
static const char *gc_color_name(uint32_t color) {
switch (color) {
case GC_BLACK: return "black";
case GC_WHITE: return "white";
case GC_GREY: return "grey";
case GC_PURPLE: return "purple";
default: return "unknown";
}
}
static void gc_trace_ref(zend_refcounted *ref) {
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object *) ref;
fprintf(stderr, "[%p] rc=%d addr=%d %s object(%s)#%d ",
ref, GC_REFCOUNT(ref), GC_ADDRESS(GC_INFO(ref)),
gc_color_name(GC_REF_GET_COLOR(ref)),
obj->ce->name->val, obj->handle);
} else if (GC_TYPE(ref) == IS_ARRAY) {
zend_array *arr = (zend_array *) ref;
fprintf(stderr, "[%p] rc=%d addr=%d %s array(%d) ",
ref, GC_REFCOUNT(ref), GC_ADDRESS(GC_INFO(ref)),
gc_color_name(GC_REF_GET_COLOR(ref)),
zend_hash_num_elements(arr));
} else {
fprintf(stderr, "[%p] rc=%d addr=%d %s %s ",
ref, GC_REFCOUNT(ref), GC_ADDRESS(GC_INFO(ref)),
gc_color_name(GC_REF_GET_COLOR(ref)),
zend_get_type_by_const(GC_TYPE(ref)));
}
}
#endif
static zend_always_inline void gc_remove_from_roots(gc_root_buffer *root)
{
GC_LINK_UNUSED(root);
GC_G(num_roots)--;
GC_BENCH_DEC(root_buf_length);
}
static void root_buffer_dtor(zend_gc_globals *gc_globals)
{
if (gc_globals->buf) {
free(gc_globals->buf);
gc_globals->buf = NULL;
}
}
static void gc_globals_ctor_ex(zend_gc_globals *gc_globals)
{
gc_globals->gc_enabled = 0;
gc_globals->gc_active = 0;
gc_globals->gc_protected = 1;
gc_globals->gc_full = 0;
gc_globals->buf = NULL;
gc_globals->buf_size = 0;
gc_globals->gc_threshold = 0;
gc_globals->unused = GC_INVALID;
gc_globals->first_unused = 0;
gc_globals->num_roots = 0;
gc_globals->gc_runs = 0;
gc_globals->collected = 0;
#if GC_BENCH
gc_globals->root_buf_length = 0;
gc_globals->root_buf_peak = 0;
gc_globals->zval_possible_root = 0;
gc_globals->zval_buffered = 0;
gc_globals->zval_remove_from_buffer = 0;
gc_globals->zval_marked_grey = 0;
#endif
}
ZEND_API void gc_globals_ctor(void)
{
#ifdef ZTS
ts_allocate_id(&gc_globals_id, sizeof(zend_gc_globals), (ts_allocate_ctor) gc_globals_ctor_ex, (ts_allocate_dtor) root_buffer_dtor);
#else
gc_globals_ctor_ex(&gc_globals);
#endif
}
ZEND_API void gc_globals_dtor(void)
{
#ifndef ZTS
root_buffer_dtor(&gc_globals);
#endif
}
ZEND_API void gc_reset(void)
{
if (GC_G(buf)) {
GC_G(gc_active) = 0;
GC_G(gc_protected) = 0;
GC_G(gc_full) = 0;
GC_G(unused) = GC_INVALID;
GC_G(first_unused) = GC_FIRST_REAL_ROOT;
GC_G(num_roots) = 0;
GC_G(gc_runs) = 0;
GC_G(collected) = 0;
#if GC_BENCH
GC_G(root_buf_length) = 0;
GC_G(root_buf_peak) = 0;
GC_G(zval_possible_root) = 0;
GC_G(zval_buffered) = 0;
GC_G(zval_remove_from_buffer) = 0;
GC_G(zval_marked_grey) = 0;
#endif
}
}
ZEND_API zend_bool gc_set_enabled(zend_bool enable)
{
zend_bool old_enabled = GC_G(gc_enabled);
GC_G(gc_enabled) = enable;
if (enable && !old_enabled && GC_G(buf) == NULL) {
GC_G(buf) = (gc_root_buffer*) malloc(sizeof(gc_root_buffer) * GC_DEFAULT_BUF_SIZE);
GC_G(buf_size) = GC_DEFAULT_BUF_SIZE;
GC_G(gc_threshold) = GC_DEFAULT_THRESHOLD + GC_FIRST_REAL_ROOT;
gc_reset();
}
return old_enabled;
}
ZEND_API zend_bool gc_enabled(void)
{
return GC_G(gc_enabled);
}
static void gc_grow_root_buffer(void)
{
size_t new_size;
if (GC_G(buf_size) >= GC_MAX_BUF_SIZE) {
if (!GC_G(gc_full)) {
zend_error(E_WARNING, "GC buffer overflow (GC disabled)\n");
//???GC_G(gc_enabled) = 0;
GC_G(gc_active) = 1;
GC_G(gc_protected) = 1;
GC_G(gc_full) = 1;
CG(unclean_shutdown) = 1;
return;
}
}
if (GC_G(buf_size) < GC_BUF_GROW_STEP) {
new_size = GC_G(buf_size) *= 2;
} else {
new_size = GC_G(buf_size) + GC_BUF_GROW_STEP;
}
if (new_size > GC_MAX_BUF_SIZE) {
new_size = GC_MAX_BUF_SIZE;
}
GC_G(buf) = perealloc(GC_G(buf), sizeof(gc_root_buffer) * new_size, 1);
GC_G(buf_size) = new_size;
}
static void gc_adjust_threshold(int count)
{
#if 0
/* TODO Very simple heuristic for dynamic GC buffer resizing:
* If there are "too few" collections, increase the collection threshold
* by a factor of two ??? */
if (count < 100) {
GC_G(gc_threshold) *= 2;
} else if (GC_G(gc_threshold) > GC_DEFAULT_THRESHOLD) {
GC_G(gc_threshold) /= 2;
}
#endif
}
static zend_never_inline void ZEND_FASTCALL gc_possible_root_when_full(zend_refcounted *ref)
{
gc_root_buffer *newRoot;
ZEND_ASSERT(GC_TYPE(ref) == IS_ARRAY || GC_TYPE(ref) == IS_OBJECT);
ZEND_ASSERT(GC_INFO(ref) == 0);
if (GC_G(gc_enabled) && !GC_G(gc_active)) {
GC_ADDREF(ref);
gc_adjust_threshold(gc_collect_cycles());
if (UNEXPECTED(GC_DELREF(ref)) == 0) {
zval_dtor_func(ref);
return;
} else if (UNEXPECTED(GC_INFO(ref))) {
return;
}
}
if (GC_HAS_UNUSED()) {
newRoot = GC_FETCH_UNUSED();
} else if (EXPECTED(GC_HAS_NEXT_UNUSED())) {
newRoot = GC_FETCH_NEXT_UNUSED();
} else {
gc_grow_root_buffer();
ZEND_ASSERT(GC_HAS_NEXT_UNUSED());
newRoot = GC_FETCH_NEXT_UNUSED();
}
GC_TRACE_SET_COLOR(ref, GC_PURPLE);
GC_REF_SET_INFO_EX(ref, newRoot, GC_PURPLE);
newRoot->ref = ref; /* GC_ROOT tag is 0 */
GC_G(num_roots)++;
GC_BENCH_INC(zval_buffered);
GC_BENCH_INC(root_buf_length);
GC_BENCH_PEAK(root_buf_peak, root_buf_length);
}
ZEND_API void ZEND_FASTCALL gc_possible_root(zend_refcounted *ref)
{
gc_root_buffer *newRoot;
if (UNEXPECTED(GC_G(gc_protected)) || UNEXPECTED(CG(unclean_shutdown))) {
return;
}
GC_BENCH_INC(zval_possible_root);
if (GC_HAS_UNUSED()) {
newRoot = GC_FETCH_UNUSED();
} else if (EXPECTED(GC_HAS_NEXT_UNUSED_UNDER_THRESHOLD())) {
newRoot = GC_FETCH_NEXT_UNUSED();
} else {
gc_possible_root_when_full(ref);
return;
}
ZEND_ASSERT(GC_TYPE(ref) == IS_ARRAY || GC_TYPE(ref) == IS_OBJECT);
ZEND_ASSERT(GC_INFO(ref) == 0);
GC_TRACE_SET_COLOR(ref, GC_PURPLE);
GC_REF_SET_INFO_EX(ref, newRoot, GC_PURPLE);
newRoot->ref = ref;
GC_G(num_roots)++;
GC_BENCH_INC(zval_buffered);
GC_BENCH_INC(root_buf_length);
GC_BENCH_PEAK(root_buf_peak, root_buf_length);
}
ZEND_API void ZEND_FASTCALL gc_remove_from_buffer(zend_refcounted *ref)
{
gc_root_buffer *root;
uint32_t addr = GC_ADDRESS(GC_INFO(ref));
ZEND_ASSERT(addr);
GC_BENCH_INC(zval_remove_from_buffer);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
GC_TRACE_SET_COLOR(ref, GC_BLACK);
}
GC_REF_SET_INFO(ref, 0);
if (UNEXPECTED(GC_NEED_COMPRESSION(addr))) {
addr = gc_decompress(ref, addr);
}
root = GC_G(buf) + addr;
gc_remove_from_roots(root);
}
static void gc_scan_black(zend_refcounted *ref)
{
HashTable *ht;
Bucket *p, *end;
zval *zv;
tail_call:
ht = NULL;
GC_REF_SET_BLACK(ref);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object_get_gc_t get_gc;
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED) &&
(get_gc = obj->handlers->get_gc) != NULL)) {
int n;
zval *zv, *end;
zval tmp;
ZVAL_OBJ(&tmp, obj);
ht = get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
if (!n) return;
while (!Z_REFCOUNTED_P(--end)) {
if (zv == end) return;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
gc_scan_black(ref);
}
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
goto tail_call;
}
return;
}
} else {
return;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if ((zend_array*)ref != &EG(symbol_table)) {
ht = (zend_array*)ref;
} else {
return;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
goto tail_call;
}
}
return;
} else {
return;
}
if (!ht->nNumUsed) return;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
end--;
zv = &end->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
break;
}
if (p == end) return;
}
while (p != end) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
gc_scan_black(ref);
}
}
p++;
}
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_GET_COLOR(ref) != GC_BLACK) {
goto tail_call;
}
}
static void gc_mark_grey(zend_refcounted *ref)
{
HashTable *ht;
Bucket *p, *end;
zval *zv;
tail_call:
if (GC_REF_GET_COLOR(ref) != GC_GREY) {
ht = NULL;
GC_BENCH_INC(zval_marked_grey);
GC_REF_SET_COLOR(ref, GC_GREY);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object_get_gc_t get_gc;
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED) &&
(get_gc = obj->handlers->get_gc) != NULL)) {
int n;
zval *zv, *end;
zval tmp;
ZVAL_OBJ(&tmp, obj);
ht = get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
if (!n) return;
while (!Z_REFCOUNTED_P(--end)) {
if (zv == end) return;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
gc_mark_grey(ref);
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
goto tail_call;
}
} else {
return;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if (((zend_array*)ref) == &EG(symbol_table)) {
GC_REF_SET_BLACK(ref);
return;
} else {
ht = (zend_array*)ref;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_DELREF(ref);
goto tail_call;
}
return;
} else {
return;
}
if (!ht->nNumUsed) return;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
end--;
zv = &end->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
break;
}
if (p == end) return;
}
while (p != end) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
gc_mark_grey(ref);
}
p++;
}
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
goto tail_call;
}
}
/* Two-Finger compaction algorithm */
static void gc_compact(void)
{
if (GC_G(num_roots) + GC_FIRST_REAL_ROOT != GC_G(first_unused)) {
if (GC_G(num_roots)) {
gc_root_buffer *buf = GC_G(buf);
uint32_t free = GC_FIRST_REAL_ROOT;
uint32_t scan = GC_G(first_unused) - 1;
uint32_t addr;
zend_refcounted *p;
while (free < scan) {
while (!GC_IS_UNUSED(buf[free].ref)) {
free++;
}
while (GC_IS_UNUSED(buf[scan].ref)) {
scan--;
}
if (scan > free) {
p = buf[scan].ref;
buf[free].ref = p;
p = GC_GET_PTR(p);
addr = free;
if (UNEXPECTED(GC_NEED_COMPRESSION(addr))) {
addr = gc_compress(addr);
}
GC_REF_SET_INFO(p, addr | GC_REF_GET_COLOR(p));
free++;
scan--;
if (scan <= GC_G(num_roots)) {
break;
}
} else {
break;
}
}
}
GC_G(unused) = GC_INVALID;
GC_G(first_unused) = GC_G(num_roots) + GC_FIRST_REAL_ROOT;
}
}
static void gc_mark_roots(void)
{
gc_root_buffer *current, *last;
gc_compact();
current = GC_G(buf) + GC_FIRST_REAL_ROOT;
last = GC_G(buf) + GC_G(first_unused);
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_GET_COLOR(current->ref) == GC_PURPLE) {
gc_mark_grey(current->ref);
}
}
current++;
}
}
static void gc_scan(zend_refcounted *ref)
{
HashTable *ht;
Bucket *p, *end;
zval *zv;
tail_call:
if (GC_REF_GET_COLOR(ref) == GC_GREY) {
if (GC_REFCOUNT(ref) > 0) {
gc_scan_black(ref);
} else {
GC_REF_SET_COLOR(ref, GC_WHITE);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object_get_gc_t get_gc;
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED) &&
(get_gc = obj->handlers->get_gc) != NULL)) {
int n;
zval *zv, *end;
zval tmp;
ZVAL_OBJ(&tmp, obj);
ht = get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
if (!n) return;
while (!Z_REFCOUNTED_P(--end)) {
if (zv == end) return;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
gc_scan(ref);
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
goto tail_call;
}
} else {
return;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if ((zend_array*)ref == &EG(symbol_table)) {
GC_REF_SET_BLACK(ref);
return;
} else {
ht = (zend_array*)ref;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
goto tail_call;
}
return;
} else {
return;
}
if (!ht->nNumUsed) return;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
end--;
zv = &end->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
break;
}
if (p == end) return;
}
while (p != end) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
gc_scan(ref);
}
p++;
}
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
goto tail_call;
}
}
}
static void gc_scan_roots(void)
{
gc_root_buffer *current = GC_G(buf) + GC_FIRST_REAL_ROOT;
gc_root_buffer *last = GC_G(buf) + GC_G(first_unused);
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
gc_scan(current->ref);
}
current++;
}
}
static void gc_add_garbage(zend_refcounted *ref)
{
gc_root_buffer *buf;
if (GC_HAS_UNUSED()) {
buf = GC_FETCH_UNUSED();
} else if (GC_HAS_NEXT_UNUSED()) {
buf = GC_FETCH_NEXT_UNUSED();
} else {
gc_grow_root_buffer();
ZEND_ASSERT(GC_HAS_NEXT_UNUSED());
buf = GC_FETCH_NEXT_UNUSED();
}
GC_REF_SET_INFO_EX(ref, buf, GC_BLACK);
buf->ref = GC_MAKE_GARBAGE(ref);
GC_G(num_roots)++;
}
static int gc_collect_white(zend_refcounted *ref, uint32_t *flags)
{
int count = 0;
HashTable *ht;
Bucket *p, *end;
zval *zv;
tail_call:
if (GC_REF_GET_COLOR(ref) == GC_WHITE) {
ht = NULL;
GC_REF_SET_BLACK(ref);
/* don't count references for compatibility ??? */
if (GC_TYPE(ref) != IS_REFERENCE) {
count++;
}
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object_get_gc_t get_gc;
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED) &&
(get_gc = obj->handlers->get_gc) != NULL)) {
int n;
zval *zv, *end;
zval tmp;
/* optimization: color is GC_BLACK (0) */
if (!GC_INFO(ref)) {
gc_add_garbage(ref);
}
if (obj->handlers->dtor_obj &&
((obj->handlers->dtor_obj != zend_objects_destroy_object) ||
(obj->ce->destructor != NULL))) {
*flags |= GC_HAS_DESTRUCTORS;
}
ZVAL_OBJ(&tmp, obj);
ht = get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
if (!n) return count;
while (!Z_REFCOUNTED_P(--end)) {
/* count non-refcounted for compatibility ??? */
if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
if (zv == end) return count;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
count += gc_collect_white(ref, flags);
/* count non-refcounted for compatibility ??? */
} else if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
goto tail_call;
}
} else {
return count;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
/* optimization: color is GC_BLACK (0) */
if (!GC_INFO(ref)) {
gc_add_garbage(ref);
}
ht = (zend_array*)ref;
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
goto tail_call;
}
return count;
} else {
return count;
}
if (!ht->nNumUsed) return count;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
end--;
zv = &end->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
break;
}
/* count non-refcounted for compatibility ??? */
if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
if (p == end) return count;
}
while (p != end) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
count += gc_collect_white(ref, flags);
/* count non-refcounted for compatibility ??? */
} else if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
p++;
}
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
goto tail_call;
}
return count;
}
static int gc_collect_roots(uint32_t *flags)
{
uint32_t n, end;
zend_refcounted *ref;
int count = 0;
gc_root_buffer *current = GC_G(buf) + GC_FIRST_REAL_ROOT;
gc_root_buffer *last = GC_G(buf) + GC_G(first_unused);
/* remove non-garbage from the list */
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_GET_COLOR(current->ref) == GC_BLACK) {
GC_REF_SET_INFO(current->ref, 0); /* reset GC_ADDRESS() and keep GC_BLACK */
gc_remove_from_roots(current);
}
}
current++;
}
gc_compact();
/* Root buffer might be reallocated during gc_collect_white,
* make sure to reload pointers. */
n = GC_FIRST_REAL_ROOT;
end = GC_G(first_unused);
while (n != end) {
current = GC_G(buf) + n;
ref = current->ref;
if (GC_IS_ROOT(ref)) {
if (GC_REF_GET_COLOR(ref) == GC_WHITE) {
current->ref = GC_MAKE_GARBAGE(ref);
count += gc_collect_white(ref, flags);
}
}
n++;
}
return count;
}
static void gc_remove_nested_data_from_buffer(zend_refcounted *ref, gc_root_buffer *root)
{
HashTable *ht = NULL;
Bucket *p, *end;
zval *zv;
tail_call:
if (root ||
(GC_ADDRESS(GC_INFO(ref)) != 0 &&
GC_REF_GET_COLOR(ref) == GC_BLACK)) {
GC_TRACE_REF(ref, "removing from buffer");
if (root) {
gc_remove_from_roots(root);
GC_REF_SET_INFO(ref, 0);
root = NULL;
} else {
GC_REMOVE_FROM_BUFFER(ref);
}
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object_get_gc_t get_gc;
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED) &&
(get_gc = obj->handlers->get_gc) != NULL)) {
int n;
zval *zv, *end;
zval tmp;
ZVAL_OBJ(&tmp, obj);
ht = get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
if (!n) return;
while (!Z_REFCOUNTED_P(--end)) {
if (zv == end) return;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
gc_remove_nested_data_from_buffer(ref, NULL);
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
goto tail_call;
}
} else {
return;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
ht = (zend_array*)ref;
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
goto tail_call;
}
return;
} else {
return;
}
if (!ht->nNumUsed) return;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
end--;
zv = &end->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
break;
}
if (p == end) return;
}
while (p != end) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
gc_remove_nested_data_from_buffer(ref, NULL);
}
p++;
}
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
goto tail_call;
}
}
ZEND_API int zend_gc_collect_cycles(void)
{
int count = 0;
if (GC_G(num_roots)) {
gc_root_buffer *current, *last;
zend_refcounted *p;
uint32_t gc_flags = 0;
uint32_t n, end;
if (GC_G(gc_active)) {
return 0;
}
GC_TRACE("Collecting cycles");
GC_G(gc_runs)++;
GC_G(gc_active) = 1;
GC_TRACE("Marking roots");
gc_mark_roots();
GC_TRACE("Scanning roots");
gc_scan_roots();
GC_TRACE("Collecting roots");
count = gc_collect_roots(&gc_flags);
if (!GC_G(num_roots)) {
/* nothing to free */
GC_TRACE("Nothing to free");
GC_G(gc_active) = 0;
return 0;
}
end = GC_G(first_unused);
if (gc_flags & GC_HAS_DESTRUCTORS) {
uint32_t *refcounts;
GC_TRACE("Calling destructors");
// TODO: may be use emalloc() ???
refcounts = pemalloc(sizeof(uint32_t) * GC_G(first_unused), 1);
/* Remember reference counters before calling destructors */
n = GC_FIRST_REAL_ROOT;
current = GC_G(buf) + GC_FIRST_REAL_ROOT;
while (n != end) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
refcounts[n] = GC_REFCOUNT(p);
}
current++;
n++;
}
/* Call destructors
*
* The root buffer might be reallocated during destructors calls,
* make sure to reload pointers as necessary. */
n = GC_FIRST_REAL_ROOT;
while (n != end) {
current = GC_G(buf) + n;
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
if (GC_TYPE(p) == IS_OBJECT
&& !(OBJ_FLAGS(p) & IS_OBJ_DESTRUCTOR_CALLED)) {
zend_object *obj = (zend_object*)p;
GC_TRACE_REF(obj, "calling destructor");
GC_ADD_FLAGS(obj, IS_OBJ_DESTRUCTOR_CALLED);
if (obj->handlers->dtor_obj
&& (obj->handlers->dtor_obj != zend_objects_destroy_object
|| obj->ce->destructor)) {
GC_ADDREF(obj);
obj->handlers->dtor_obj(obj);
GC_DELREF(obj);
}
}
}
n++;
}
/* Remove values captured in destructors */
n = GC_FIRST_REAL_ROOT;
current = GC_G(buf) + GC_FIRST_REAL_ROOT;
last = GC_G(buf) + GC_G(first_unused);
while (n != end) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
if (GC_REFCOUNT(p) > refcounts[n]) {
gc_remove_nested_data_from_buffer(p, current);
}
}
current++;
n++;
}
pefree(refcounts, 1);
}
/* Destroy zvals */
GC_TRACE("Destroying zvals");
GC_G(gc_protected) = 1;
current = GC_G(buf) + GC_FIRST_REAL_ROOT;
last = GC_G(buf) + GC_G(first_unused);
while (current != last) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
GC_TRACE_REF(p, "destroying");
if (GC_TYPE(p) == IS_OBJECT) {
zend_object *obj = (zend_object*)p;
EG(objects_store).object_buckets[obj->handle] = SET_OBJ_INVALID(obj);
GC_TYPE_INFO(obj) = IS_NULL |
(GC_TYPE_INFO(obj) & ~GC_TYPE_MASK);
if (!(OBJ_FLAGS(obj) & IS_OBJ_FREE_CALLED)) {
GC_ADD_FLAGS(obj, IS_OBJ_FREE_CALLED);
if (obj->handlers->free_obj) {
GC_ADDREF(obj);
obj->handlers->free_obj(obj);
GC_DELREF(obj);
}
}
SET_OBJ_BUCKET_NUMBER(EG(objects_store).object_buckets[obj->handle], EG(objects_store).free_list_head);
EG(objects_store).free_list_head = obj->handle;
current->ref = GC_MAKE_GARBAGE(((char*)obj) - obj->handlers->offset);
} else if (GC_TYPE(p) == IS_ARRAY) {
zend_array *arr = (zend_array*)p;
GC_TYPE_INFO(arr) = IS_NULL |
(GC_TYPE_INFO(arr) & ~GC_TYPE_MASK);
/* GC may destroy arrays with rc>1. This is valid and safe. */
HT_ALLOW_COW_VIOLATION(arr);
zend_hash_destroy(arr);
}
}
current++;
}
/* Free objects */
current = GC_G(buf) + GC_FIRST_REAL_ROOT;
while (current != last) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
GC_LINK_UNUSED(current);
GC_G(num_roots)--;
efree(p);
}
current++;
}
GC_TRACE("Collection finished");
GC_G(collected) += count;
GC_G(gc_protected) = 0;
GC_G(gc_active) = 0;
}
gc_compact();
return count;
}
/*
* Local variables:
* tab-width: 4
* c-basic-offset: 4
* indent-tabs-mode: t
* End:
* vim600: sw=4 ts=4 fdm=marker
* vim<600: sw=4 ts=4
*
* vim:noexpandtab:
*/
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