path: root/mono/metadata/sgen-gc.h

/*
 * sgen-gc.c: Simple generational GC.
 *
 * Copyright 2001-2003 Ximian, Inc
 * Copyright 2003-2010 Novell, Inc.
 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
 * Copyright (C) 2012 Xamarin Inc
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License 2.0 as published by the Free Software Foundation;
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License 2.0 along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#ifndef __MONO_SGENGC_H__
#define __MONO_SGENGC_H__

/* pthread impl */
#include "config.h"

#ifdef HAVE_SGEN_GC

typedef struct _SgenThreadInfo SgenThreadInfo;
#define THREAD_INFO_TYPE SgenThreadInfo

#include <glib.h>
#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif
#include <signal.h>
#include <mono/utils/mono-compiler.h>
#include <mono/utils/mono-threads.h>
#include <mono/utils/dtrace.h>
#include <mono/utils/mono-logger-internal.h>
#include <mono/utils/atomic.h>
#include <mono/utils/mono-mutex.h>
#include <mono/metadata/class-internals.h>
#include <mono/metadata/object-internals.h>
#include <mono/metadata/sgen-conf.h>
#include <mono/metadata/sgen-archdep.h>
#include <mono/metadata/sgen-descriptor.h>
#include <mono/metadata/sgen-gray.h>
#include <mono/metadata/sgen-hash-table.h>

/* The method used to clear the nursery */
/* Clearing at nursery collections is the safest, but has bad interactions with caches.
 * Clearing at TLAB creation is much faster, but more complex and it might expose hard
 * to find bugs.
 */
typedef enum {
	CLEAR_AT_GC,
	CLEAR_AT_TLAB_CREATION
} NurseryClearPolicy;

NurseryClearPolicy sgen_get_nursery_clear_policy (void) MONO_INTERNAL;

#define SGEN_TV_DECLARE(name) gint64 name
#define SGEN_TV_GETTIME(tv) tv = mono_100ns_ticks ()
#define SGEN_TV_ELAPSED(start,end) (int)((end-start) / 10)
#define SGEN_TV_ELAPSED_MS(start,end) ((SGEN_TV_ELAPSED((start),(end)) + 500) / 1000)

#if !defined(__MACH__) && !MONO_MACH_ARCH_SUPPORTED && defined(HAVE_PTHREAD_KILL)
#define SGEN_POSIX_STW 1
#endif

/* eventually share with MonoThread? */
/*
 * This structure extends the MonoThreadInfo structure.
 */
struct _SgenThreadInfo {
	MonoThreadInfo info;
	/*
	This is set to TRUE when STW fails to suspend a thread, most probably because the
	underlying thread is dead.
	*/
	int skip;
	volatile int in_critical_region;

	/*
	This is set the argument of mono_gc_set_skip_thread.

	A thread that knowingly holds no managed state can call this
	function around blocking loops to reduce the GC burden by not
	been scanned.
	*/
	gboolean gc_disabled;
	void *stack_end;
	void *stack_start;
	void *stack_start_limit;
	char **tlab_next_addr;
	char **tlab_start_addr;
	char **tlab_temp_end_addr;
	char **tlab_real_end_addr;
	gpointer runtime_data;

#ifdef SGEN_POSIX_STW
	/* This is -1 until the first suspend. */
	int signal;
	/* FIXME: kill this, we only use signals on systems that have rt-posix, which doesn't have issues with duplicates. */
	unsigned int stop_count; /* to catch duplicate signals. */
#endif

	gpointer stopped_ip;	/* only valid if the thread is stopped */
	MonoDomain *stopped_domain; /* dsto */

	/*FIXME pretty please finish killing ARCH_NUM_REGS */
#ifdef USE_MONO_CTX
	MonoContext ctx;		/* ditto */
#else
	gpointer regs[ARCH_NUM_REGS];	    /* ditto */
#endif

#ifndef HAVE_KW_THREAD
	char *tlab_start;
	char *tlab_next;
	char *tlab_temp_end;
	char *tlab_real_end;
#endif
};

/*
 * The nursery section uses this struct.
 */
typedef struct _GCMemSection GCMemSection;
struct _GCMemSection {
	char *data;
	mword size;
	/* pointer where more data could be allocated if it fits */
	char *next_data;
	char *end_data;
	/*
	 * scan starts is an array of pointers to objects equally spaced in the allocation area
	 * They let use quickly find pinned objects from pinning pointers.
	 */
	char **scan_starts;
	/* in major collections indexes in the pin_queue for objects that pin this section */
	void **pin_queue_start;
	int pin_queue_num_entries;
	unsigned int num_scan_start;
};

/*
 * Recursion is not allowed for the thread lock.
 */
#define LOCK_DECLARE(name) mono_mutex_t name
/* if changing LOCK_INIT to something that isn't idempotent, look at
   its use in mono_gc_base_init in sgen-gc.c */
#define LOCK_INIT(name)	mono_mutex_init (&(name))
#define LOCK_GC do {						\
		mono_mutex_lock (&gc_mutex);			\
		MONO_GC_LOCKED ();				\
	} while (0)
#define TRYLOCK_GC (mono_mutex_trylock (&gc_mutex) == 0)
#define UNLOCK_GC do { sgen_gc_unlock (); } while (0)

extern LOCK_DECLARE (sgen_interruption_mutex);

#define LOCK_INTERRUPTION mono_mutex_lock (&sgen_interruption_mutex)
#define UNLOCK_INTERRUPTION mono_mutex_unlock (&sgen_interruption_mutex)

/* FIXME: Use InterlockedAdd & InterlockedAdd64 to reduce the CAS cost. */
#define SGEN_CAS_PTR	InterlockedCompareExchangePointer
#define SGEN_ATOMIC_ADD(x,i)	do {					\
		int __old_x;						\
		do {							\
			__old_x = (x);					\
		} while (InterlockedCompareExchange (&(x), __old_x + (i), __old_x) != __old_x); \
	} while (0)
#define SGEN_ATOMIC_ADD_P(x,i) do { \
		size_t __old_x;                                            \
		do {                                                    \
			__old_x = (x);                                  \
		} while (InterlockedCompareExchangePointer ((void**)&(x), (void*)(__old_x + (i)), (void*)__old_x) != (void*)__old_x); \
	} while (0)


#ifndef HOST_WIN32
/* we intercept pthread_create calls to know which threads exist */
#define USE_PTHREAD_INTERCEPT 1
#endif

#ifdef HEAVY_STATISTICS
#define HEAVY_STAT(x)	x

extern long long stat_objects_alloced_degraded;
extern long long stat_bytes_alloced_degraded;
extern long long stat_copy_object_called_major;
extern long long stat_objects_copied_major;
#else
#define HEAVY_STAT(x)
#endif

#define SGEN_ASSERT(level, a, ...) do {	\
	if (G_UNLIKELY ((level) <= SGEN_MAX_ASSERT_LEVEL && !(a))) {	\
		g_error (__VA_ARGS__);	\
} } while (0)


#define SGEN_LOG(level, format, ...) do {      \
	if (G_UNLIKELY ((level) <= SGEN_MAX_DEBUG_LEVEL && (level) <= gc_debug_level)) {	\
		mono_gc_printf (gc_debug_file, format, ##__VA_ARGS__);	\
} } while (0)

#define SGEN_COND_LOG(level, cond, format, ...) do {	\
	if (G_UNLIKELY ((level) <= SGEN_MAX_DEBUG_LEVEL && (level) <= gc_debug_level)) {	\
		if (cond)	\
			mono_gc_printf (gc_debug_file, format, ##__VA_ARGS__);	\
} } while (0)

#define SGEN_LOG_DO(level, fun) do {	\
	if (G_UNLIKELY ((level) <= SGEN_MAX_DEBUG_LEVEL && (level) <= gc_debug_level)) {	\
		fun;	\
} } while (0)

extern int gc_debug_level;
extern FILE* gc_debug_file;

extern int current_collection_generation;

extern unsigned int sgen_global_stop_count;

extern gboolean bridge_processing_in_progress;

extern int num_ready_finalizers;

#define SGEN_ALLOC_ALIGN		8
#define SGEN_ALLOC_ALIGN_BITS	3

#define SGEN_ALIGN_UP(s)		(((s)+(SGEN_ALLOC_ALIGN-1)) & ~(SGEN_ALLOC_ALIGN-1))

/*
 * The link pointer is hidden by negating each bit.  We use the lowest
 * bit of the link (before negation) to store whether it needs
 * resurrection tracking.
 */
#define HIDE_POINTER(p,t)	((gpointer)(~((gulong)(p)|((t)?1:0))))
#define REVEAL_POINTER(p)	((gpointer)((~(gulong)(p))&~3L))

#ifdef SGEN_ALIGN_NURSERY
#define SGEN_PTR_IN_NURSERY(p,bits,start,end)	(((mword)(p) & ~((1 << (bits)) - 1)) == (mword)(start))
#else
#define SGEN_PTR_IN_NURSERY(p,bits,start,end)	((char*)(p) >= (start) && (char*)(p) < (end))
#endif

#ifdef USER_CONFIG

/* good sizes are 512KB-1MB: larger ones increase a lot memzeroing time */
#define DEFAULT_NURSERY_SIZE (sgen_nursery_size)
extern int sgen_nursery_size MONO_INTERNAL;
#ifdef SGEN_ALIGN_NURSERY
/* The number of trailing 0 bits in DEFAULT_NURSERY_SIZE */
#define DEFAULT_NURSERY_BITS (sgen_nursery_bits)
extern int sgen_nursery_bits MONO_INTERNAL;
#endif

#else

#define DEFAULT_NURSERY_SIZE (4*1024*1024)
#ifdef SGEN_ALIGN_NURSERY
#define DEFAULT_NURSERY_BITS 22
#endif

#endif

#ifndef SGEN_ALIGN_NURSERY
#define DEFAULT_NURSERY_BITS -1
#endif

extern char *sgen_nursery_start MONO_INTERNAL;
extern char *sgen_nursery_end MONO_INTERNAL;

static inline MONO_ALWAYS_INLINE gboolean
sgen_ptr_in_nursery (void *p)
{
	return SGEN_PTR_IN_NURSERY ((p), DEFAULT_NURSERY_BITS, sgen_nursery_start, sgen_nursery_end);
}

static inline MONO_ALWAYS_INLINE char*
sgen_get_nursery_start (void)
{
	return sgen_nursery_start;
}

static inline MONO_ALWAYS_INLINE char*
sgen_get_nursery_end (void)
{
	return sgen_nursery_end;
}

/* Structure that corresponds to a MonoVTable: desc is a mword so requires
 * no cast from a pointer to an integer
 */
typedef struct {
	MonoClass *klass;
	mword desc;
} GCVTable;

/* these bits are set in the object vtable: we could merge them since an object can be
 * either pinned or forwarded but not both.
 * We store them in the vtable slot because the bits are used in the sync block for
 * other purposes: if we merge them and alloc the sync blocks aligned to 8 bytes, we can change
 * this and use bit 3 in the syncblock (with the lower two bits both set for forwarded, that
 * would be an invalid combination for the monitor and hash code).
 * The values are already shifted.
 * The forwarding address is stored in the sync block.
 */
#define SGEN_FORWARDED_BIT 1
#define SGEN_PINNED_BIT 2
#define SGEN_VTABLE_BITS_MASK 0x3

/* returns NULL if not forwarded, or the forwarded address */
#define SGEN_OBJECT_IS_FORWARDED(obj) (((mword*)(obj))[0] & SGEN_FORWARDED_BIT ? (void*)(((mword*)(obj))[0] & ~SGEN_VTABLE_BITS_MASK) : NULL)
#define SGEN_OBJECT_IS_PINNED(obj) (((mword*)(obj))[0] & SGEN_PINNED_BIT)

/* set the forwarded address fw_addr for object obj */
#define SGEN_FORWARD_OBJECT(obj,fw_addr) do {				\
		((mword*)(obj))[0] = (mword)(fw_addr) | SGEN_FORWARDED_BIT; \
	} while (0)
#define SGEN_PIN_OBJECT(obj) do {	\
		((mword*)(obj))[0] |= SGEN_PINNED_BIT;	\
	} while (0)
#define SGEN_UNPIN_OBJECT(obj) do {	\
		((mword*)(obj))[0] &= ~SGEN_PINNED_BIT;	\
	} while (0)

/*
 * Since we set bits in the vtable, use the macro to load it from the pointer to
 * an object that is potentially pinned.
 */
#define SGEN_LOAD_VTABLE(addr) ((*(mword*)(addr)) & ~SGEN_VTABLE_BITS_MASK)

#if defined(SGEN_GRAY_OBJECT_ENQUEUE) || SGEN_MAX_DEBUG_LEVEL >= 9
#define GRAY_OBJECT_ENQUEUE sgen_gray_object_enqueue
#define GRAY_OBJECT_DEQUEUE(queue,o) ((o) = sgen_gray_object_dequeue ((queue)))
#else
#define GRAY_OBJECT_ENQUEUE(queue,o) do {				\
		if (G_UNLIKELY (!(queue)->first || (queue)->first->end == SGEN_GRAY_QUEUE_SECTION_SIZE)) \
			sgen_gray_object_enqueue ((queue), (o));	\
		else							\
			(queue)->first->objects [(queue)->first->end++] = (o); \
		PREFETCH ((o));						\
	} while (0)
#define GRAY_OBJECT_DEQUEUE(queue,o) do {				\
		if (!(queue)->first)					\
			(o) = NULL;					\
		else if (G_UNLIKELY ((queue)->first->end == 1))		\
			(o) = sgen_gray_object_dequeue ((queue));		\
		else							\
			(o) = (queue)->first->objects [--(queue)->first->end]; \
	} while (0)
#endif

/*
List of what each bit on of the vtable gc bits means. 
*/
enum {
	SGEN_GC_BIT_BRIDGE_OBJECT = 1,
};

/* the runtime can register areas of memory as roots: we keep two lists of roots,
 * a pinned root set for conservatively scanned roots and a normal one for
 * precisely scanned roots (currently implemented as a single list).
 */
typedef struct _RootRecord RootRecord;
struct _RootRecord {
	char *end_root;
	mword root_desc;
};

enum {
	ROOT_TYPE_NORMAL = 0, /* "normal" roots */
	ROOT_TYPE_PINNED = 1, /* roots without a GC descriptor */
	ROOT_TYPE_WBARRIER = 2, /* roots with a write barrier */
	ROOT_TYPE_NUM
};

extern SgenHashTable roots_hash [ROOT_TYPE_NUM];

typedef void (*IterateObjectCallbackFunc) (char*, size_t, void*);

int sgen_thread_handshake (BOOL suspend) MONO_INTERNAL;
gboolean sgen_suspend_thread (SgenThreadInfo *info) MONO_INTERNAL;
gboolean sgen_resume_thread (SgenThreadInfo *info) MONO_INTERNAL;
void sgen_wait_for_suspend_ack (int count) MONO_INTERNAL;
void sgen_os_init (void) MONO_INTERNAL;

gboolean sgen_is_worker_thread (MonoNativeThreadId thread) MONO_INTERNAL;

void sgen_update_heap_boundaries (mword low, mword high) MONO_INTERNAL;

void sgen_scan_area_with_callback (char *start, char *end, IterateObjectCallbackFunc callback, void *data, gboolean allow_flags) MONO_INTERNAL;
void sgen_check_section_scan_starts (GCMemSection *section) MONO_INTERNAL;

/* Keep in sync with description_for_type() in sgen-internal.c! */
enum {
	INTERNAL_MEM_PIN_QUEUE,
	INTERNAL_MEM_FRAGMENT,
	INTERNAL_MEM_SECTION,
	INTERNAL_MEM_SCAN_STARTS,
	INTERNAL_MEM_FIN_TABLE,
	INTERNAL_MEM_FINALIZE_ENTRY,
	INTERNAL_MEM_FINALIZE_READY_ENTRY,
	INTERNAL_MEM_DISLINK_TABLE,
	INTERNAL_MEM_DISLINK,
	INTERNAL_MEM_ROOTS_TABLE,
	INTERNAL_MEM_ROOT_RECORD,
	INTERNAL_MEM_STATISTICS,
	INTERNAL_MEM_STAT_PINNED_CLASS,
	INTERNAL_MEM_STAT_REMSET_CLASS,
	INTERNAL_MEM_GRAY_QUEUE,
	INTERNAL_MEM_MS_TABLES,
	INTERNAL_MEM_MS_BLOCK_INFO,
	INTERNAL_MEM_MS_BLOCK_INFO_SORT,
	INTERNAL_MEM_EPHEMERON_LINK,
	INTERNAL_MEM_WORKER_DATA,
	INTERNAL_MEM_WORKER_JOB_DATA,
	INTERNAL_MEM_BRIDGE_DATA,
	INTERNAL_MEM_BRIDGE_HASH_TABLE,
	INTERNAL_MEM_BRIDGE_HASH_TABLE_ENTRY,
	INTERNAL_MEM_BRIDGE_ALIVE_HASH_TABLE,
	INTERNAL_MEM_BRIDGE_ALIVE_HASH_TABLE_ENTRY,
	INTERNAL_MEM_JOB_QUEUE_ENTRY,
	INTERNAL_MEM_TOGGLEREF_DATA,
	INTERNAL_MEM_CARDTABLE_MOD_UNION,
	INTERNAL_MEM_BINARY_PROTOCOL,
	INTERNAL_MEM_MAX
};

enum {
	GENERATION_NURSERY,
	GENERATION_OLD,
	GENERATION_MAX
};

#ifdef SGEN_BINARY_PROTOCOL
#define BINARY_PROTOCOL_ARG(x)	,x
#else
#define BINARY_PROTOCOL_ARG(x)
#endif

void sgen_init_internal_allocator (void) MONO_INTERNAL;

typedef struct _ObjectList ObjectList;
struct _ObjectList {
	MonoObject *obj;
	ObjectList *next;
};

typedef void (*CopyOrMarkObjectFunc) (void**, SgenGrayQueue*);
typedef void (*ScanObjectFunc) (char*, SgenGrayQueue*);
typedef void (*ScanVTypeFunc) (char*, mword desc, SgenGrayQueue* BINARY_PROTOCOL_ARG (size_t size));

typedef struct
{
	ScanObjectFunc scan_func;
	CopyOrMarkObjectFunc copy_func;
	SgenGrayQueue *queue;
} ScanCopyContext;

void sgen_report_internal_mem_usage (void) MONO_INTERNAL;
void sgen_dump_internal_mem_usage (FILE *heap_dump_file) MONO_INTERNAL;
void sgen_dump_section (GCMemSection *section, const char *type) MONO_INTERNAL;
void sgen_dump_occupied (char *start, char *end, char *section_start) MONO_INTERNAL;

void sgen_register_moved_object (void *obj, void *destination) MONO_INTERNAL;

void sgen_register_fixed_internal_mem_type (int type, size_t size) MONO_INTERNAL;

void* sgen_alloc_internal (int type) MONO_INTERNAL;
void sgen_free_internal (void *addr, int type) MONO_INTERNAL;

void* sgen_alloc_internal_dynamic (size_t size, int type, gboolean assert_on_failure) MONO_INTERNAL;
void sgen_free_internal_dynamic (void *addr, size_t size, int type) MONO_INTERNAL;

void** sgen_find_optimized_pin_queue_area (void *start, void *end, int *num) MONO_INTERNAL;
void sgen_find_section_pin_queue_start_end (GCMemSection *section) MONO_INTERNAL;
void sgen_pin_objects_in_section (GCMemSection *section, ScanCopyContext ctx) MONO_INTERNAL;

void sgen_pin_stats_register_object (char *obj, size_t size);
void sgen_pin_stats_register_global_remset (char *obj);
void sgen_pin_stats_print_class_stats (void);

void sgen_sort_addresses (void **array, int size) MONO_INTERNAL;
void sgen_add_to_global_remset (gpointer ptr, gpointer obj) MONO_INTERNAL;

int sgen_get_current_collection_generation (void) MONO_INTERNAL;
gboolean sgen_collection_is_parallel (void) MONO_INTERNAL;
gboolean sgen_collection_is_concurrent (void) MONO_INTERNAL;
gboolean sgen_concurrent_collection_in_progress (void) MONO_INTERNAL;

typedef struct {
	CopyOrMarkObjectFunc copy_or_mark_object;
	ScanObjectFunc scan_object;
	ScanVTypeFunc scan_vtype;
	/*FIXME add allocation function? */
} SgenObjectOperations;

SgenObjectOperations *sgen_get_current_object_ops (void) MONO_INTERNAL;

typedef struct _SgenFragment SgenFragment;

struct _SgenFragment {
	SgenFragment *next;
	char *fragment_start;
	char *fragment_next; /* the current soft limit for allocation */
	char *fragment_end;
	SgenFragment *next_in_order; /* We use a different entry for all active fragments so we can avoid SMR. */
};

typedef struct {
	SgenFragment *alloc_head; /* List head to be used when allocating memory. Walk with fragment_next. */
	SgenFragment *region_head; /* List head of the region used by this allocator. Walk with next_in_order. */
} SgenFragmentAllocator;

void sgen_fragment_allocator_add (SgenFragmentAllocator *allocator, char *start, char *end) MONO_INTERNAL;
void sgen_fragment_allocator_release (SgenFragmentAllocator *allocator) MONO_INTERNAL;
void* sgen_fragment_allocator_serial_alloc (SgenFragmentAllocator *allocator, size_t size) MONO_INTERNAL;
void* sgen_fragment_allocator_par_alloc (SgenFragmentAllocator *allocator, size_t size) MONO_INTERNAL;
void* sgen_fragment_allocator_serial_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size) MONO_INTERNAL;
void* sgen_fragment_allocator_par_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size) MONO_INTERNAL;
SgenFragment* sgen_fragment_allocator_alloc (void) MONO_INTERNAL;
void sgen_clear_allocator_fragments (SgenFragmentAllocator *allocator) MONO_INTERNAL;
void sgen_clear_range (char *start, char *end) MONO_INTERNAL;


/*
This is a space/speed compromise as we need to make sure the from/to space check is both O(1)
and only hit cache hot memory. On a 4Mb nursery it requires 1024 bytes, or 3% of your average
L1 cache. On small configs with a 512kb nursery, this goes to 0.4%.

Experimental results on how much space we waste with a 4Mb nursery:

Note that the wastage applies to the half nursery, or 2Mb:

Test 1 (compiling corlib):
9: avg: 3.1k
8: avg: 1.6k

*/
#define SGEN_TO_SPACE_GRANULE_BITS 9
#define SGEN_TO_SPACE_GRANULE_IN_BYTES (1 << SGEN_TO_SPACE_GRANULE_BITS)

extern char *sgen_space_bitmap MONO_INTERNAL;
extern int sgen_space_bitmap_size MONO_INTERNAL;

static inline gboolean
sgen_nursery_is_to_space (char *object)
{
	int idx = (object - sgen_nursery_start) >> SGEN_TO_SPACE_GRANULE_BITS;
	int byte = idx / 8;
	int bit = idx & 0x7;

	SGEN_ASSERT (4, sgen_ptr_in_nursery (object), "object %p is not in nursery [%p - %p]", object, sgen_get_nursery_start (), sgen_get_nursery_end ());
	SGEN_ASSERT (4, byte < sgen_space_bitmap_size, "byte index %d out of range", byte, sgen_space_bitmap_size);

	return (sgen_space_bitmap [byte] & (1 << bit)) != 0;
}

static inline gboolean
sgen_nursery_is_from_space (char *object)
{
	return !sgen_nursery_is_to_space (object);
}

static inline gboolean
sgen_nursery_is_object_alive (char *obj)
{
	/* FIXME put this asserts under a non default level */
	g_assert (sgen_ptr_in_nursery (obj));

	if (sgen_nursery_is_to_space (obj))
		return TRUE;

	if (SGEN_OBJECT_IS_PINNED (obj) || SGEN_OBJECT_IS_FORWARDED (obj))
		return TRUE;

	return FALSE;
}

typedef struct {
	gboolean is_split;

	char* (*alloc_for_promotion) (MonoVTable *vtable, char *obj, size_t objsize, gboolean has_references);
	char* (*par_alloc_for_promotion) (MonoVTable *vtable, char *obj, size_t objsize, gboolean has_references);

	SgenObjectOperations serial_ops;
	SgenObjectOperations parallel_ops;

	void (*prepare_to_space) (char *to_space_bitmap, int space_bitmap_size);
	void (*clear_fragments) (void);
	SgenFragment* (*build_fragments_get_exclude_head) (void);
	void (*build_fragments_release_exclude_head) (void);
	void (*build_fragments_finish) (SgenFragmentAllocator *allocator);
	void (*init_nursery) (SgenFragmentAllocator *allocator, char *start, char *end);

	gboolean (*handle_gc_param) (const char *opt); /* Optional */
	void (*print_gc_param_usage) (void); /* Optional */
} SgenMinorCollector;

extern SgenMinorCollector sgen_minor_collector;

void sgen_simple_nursery_init (SgenMinorCollector *collector) MONO_INTERNAL;
void sgen_split_nursery_init (SgenMinorCollector *collector) MONO_INTERNAL;

typedef void (*sgen_cardtable_block_callback) (mword start, mword size);
void sgen_major_collector_iterate_live_block_ranges (sgen_cardtable_block_callback callback) MONO_INTERNAL;

typedef struct _SgenMajorCollector SgenMajorCollector;
struct _SgenMajorCollector {
	size_t section_size;
	gboolean is_parallel;
	gboolean is_concurrent;
	gboolean supports_cardtable;
	gboolean sweeps_lazily;

	/*
	 * This is set to TRUE if the sweep for the last major
	 * collection has been completed.
	 */
	gboolean *have_swept;
	/*
	 * This is set to TRUE by the sweep if the next major
	 * collection should be synchronous (for evacuation).  For
	 * non-concurrent collectors, this should be NULL.
	 */
	gboolean *want_synchronous_collection;

	void* (*alloc_heap) (mword nursery_size, mword nursery_align, int nursery_bits);
	gboolean (*is_object_live) (char *obj);
	void* (*alloc_small_pinned_obj) (MonoVTable *vtable, size_t size, gboolean has_references);
	void* (*alloc_degraded) (MonoVTable *vtable, size_t size);

	SgenObjectOperations major_ops;
	SgenObjectOperations major_concurrent_ops;

	void* (*alloc_object) (MonoVTable *vtable, int size, gboolean has_references);
	void* (*par_alloc_object) (MonoVTable *vtable, int size, gboolean has_references);
	void (*free_pinned_object) (char *obj, size_t size);
	void (*iterate_objects) (gboolean non_pinned, gboolean pinned, IterateObjectCallbackFunc callback, void *data);
	void (*free_non_pinned_object) (char *obj, size_t size);
	void (*find_pin_queue_start_ends) (SgenGrayQueue *queue);
	void (*pin_objects) (SgenGrayQueue *queue);
	void (*pin_major_object) (char *obj, SgenGrayQueue *queue);
	void (*scan_card_table) (gboolean mod_union, SgenGrayQueue *queue);
	void (*iterate_live_block_ranges) (sgen_cardtable_block_callback callback);
	void (*update_cardtable_mod_union) (void);
	void (*init_to_space) (void);
	void (*sweep) (void);
	void (*check_scan_starts) (void);
	void (*dump_heap) (FILE *heap_dump_file);
	gint64 (*get_used_size) (void);
	void (*start_nursery_collection) (void);
	void (*finish_nursery_collection) (void);
	void (*start_major_collection) (void);
	void (*finish_major_collection) (void);
	void (*have_computed_minor_collection_allowance) (void);
	gboolean (*ptr_is_in_non_pinned_space) (char *ptr, char **start);
	gboolean (*obj_is_from_pinned_alloc) (char *obj);
	void (*report_pinned_memory_usage) (void);
	int (*get_num_major_sections) (void);
	gboolean (*handle_gc_param) (const char *opt);
	void (*print_gc_param_usage) (void);
	gboolean (*is_worker_thread) (MonoNativeThreadId thread);
	void (*post_param_init) (SgenMajorCollector *collector);
	void* (*alloc_worker_data) (void);
	void (*init_worker_thread) (void *data);
	void (*reset_worker_data) (void *data);
	gboolean (*is_valid_object) (char *object);
	MonoVTable* (*describe_pointer) (char *pointer);
	guint8* (*get_cardtable_mod_union_for_object) (char *object);
	long long (*get_and_reset_num_major_objects_marked) (void);
};

extern SgenMajorCollector major_collector;

void sgen_marksweep_init (SgenMajorCollector *collector) MONO_INTERNAL;
void sgen_marksweep_fixed_init (SgenMajorCollector *collector) MONO_INTERNAL;
void sgen_marksweep_par_init (SgenMajorCollector *collector) MONO_INTERNAL;
void sgen_marksweep_fixed_par_init (SgenMajorCollector *collector) MONO_INTERNAL;
void sgen_marksweep_conc_init (SgenMajorCollector *collector) MONO_INTERNAL;
SgenMajorCollector* sgen_get_major_collector (void) MONO_INTERNAL;


typedef struct {
	void (*wbarrier_set_field) (MonoObject *obj, gpointer field_ptr, MonoObject* value);
	void (*wbarrier_set_arrayref) (MonoArray *arr, gpointer slot_ptr, MonoObject* value);
	void (*wbarrier_arrayref_copy) (gpointer dest_ptr, gpointer src_ptr, int count);
	void (*wbarrier_value_copy) (gpointer dest, gpointer src, int count, MonoClass *klass);
	void (*wbarrier_object_copy) (MonoObject* obj, MonoObject *src);
	void (*wbarrier_generic_nostore) (gpointer ptr);
	void (*record_pointer) (gpointer ptr);

	void (*finish_scan_remsets) (void *start_nursery, void *end_nursery, SgenGrayQueue *queue);

	void (*prepare_for_major_collection) (void);

	void (*finish_minor_collection) (void);
	gboolean (*find_address) (char *addr);
	gboolean (*find_address_with_cards) (char *cards_start, guint8 *cards, char *addr);
} SgenRemeberedSet;

SgenRemeberedSet *sgen_get_remset (void) MONO_INTERNAL;

static guint /*__attribute__((noinline)) not sure if this hint is a good idea*/
slow_object_get_size (MonoVTable *vtable, MonoObject* o)
{
	MonoClass *klass = vtable->klass;

	/*
	 * We depend on mono_string_length_fast and
	 * mono_array_length_fast not using the object's vtable.
	 */
	if (klass == mono_defaults.string_class) {
		return sizeof (MonoString) + 2 * mono_string_length_fast ((MonoString*) o) + 2;
	} else if (klass->rank) {
		MonoArray *array = (MonoArray*)o;
		size_t size = sizeof (MonoArray) + klass->sizes.element_size * mono_array_length_fast (array);
		if (G_UNLIKELY (array->bounds)) {
			size += sizeof (mono_array_size_t) - 1;
			size &= ~(sizeof (mono_array_size_t) - 1);
			size += sizeof (MonoArrayBounds) * klass->rank;
		}
		return size;
	} else {
		/* from a created object: the class must be inited already */
		return klass->instance_size;
	}
}

/*
 * This function can be called on an object whose first word, the
 * vtable field, is not intact.  This is necessary for the parallel
 * collector.
 */
static inline guint
sgen_par_object_get_size (MonoVTable *vtable, MonoObject* o)
{
	mword descr = (mword)vtable->gc_descr;
	mword type = descr & 0x7;

	if (type == DESC_TYPE_RUN_LENGTH || type == DESC_TYPE_SMALL_BITMAP) {
		mword size = descr & 0xfff8;
		if (size == 0) /* This is used to encode a string */
			return sizeof (MonoString) + 2 * mono_string_length_fast ((MonoString*) o) + 2;
		return size;
	} else if (type == DESC_TYPE_VECTOR) {
		int element_size = ((descr) >> VECTOR_ELSIZE_SHIFT) & MAX_ELEMENT_SIZE;
		MonoArray *array = (MonoArray*)o;
		size_t size = sizeof (MonoArray) + element_size * mono_array_length_fast (array);

		if (descr & VECTOR_KIND_ARRAY) {
			size += sizeof (mono_array_size_t) - 1;
			size &= ~(sizeof (mono_array_size_t) - 1);
			size += sizeof (MonoArrayBounds) * vtable->klass->rank;
		}
		return size;
	}

	return slow_object_get_size (vtable, o);
}

static inline guint
sgen_safe_object_get_size (MonoObject *obj)
{
       char *forwarded;

       if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj)))
               obj = (MonoObject*)forwarded;

       return sgen_par_object_get_size ((MonoVTable*)SGEN_LOAD_VTABLE (obj), obj);
}

const char* sgen_safe_name (void* obj) MONO_INTERNAL;

gboolean sgen_object_is_live (void *obj) MONO_INTERNAL;

void  sgen_init_fin_weak_hash (void) MONO_INTERNAL;

gboolean sgen_need_bridge_processing (void) MONO_INTERNAL;
void sgen_bridge_reset_data (void) MONO_INTERNAL;
void sgen_bridge_processing_stw_step (void) MONO_INTERNAL;
void sgen_bridge_processing_finish (int generation) MONO_INTERNAL;
void sgen_register_test_bridge_callbacks (const char *bridge_class_name) MONO_INTERNAL;
gboolean sgen_is_bridge_object (MonoObject *obj) MONO_INTERNAL;
gboolean sgen_is_bridge_class (MonoClass *class) MONO_INTERNAL;
void sgen_mark_bridge_object (MonoObject *obj) MONO_INTERNAL;
void sgen_bridge_register_finalized_object (MonoObject *object) MONO_INTERNAL;
void sgen_bridge_describe_pointer (MonoObject *object) MONO_INTERNAL;

void sgen_scan_togglerefs (char *start, char *end, ScanCopyContext ctx) MONO_INTERNAL;
void sgen_process_togglerefs (void) MONO_INTERNAL;

typedef mono_bool (*WeakLinkAlivePredicateFunc) (MonoObject*, void*);

void sgen_null_links_with_predicate (int generation, WeakLinkAlivePredicateFunc predicate, void *data) MONO_INTERNAL;

gboolean sgen_gc_is_object_ready_for_finalization (void *object) MONO_INTERNAL;
void sgen_gc_lock (void) MONO_INTERNAL;
void sgen_gc_unlock (void) MONO_INTERNAL;
void sgen_gc_event_moves (void) MONO_INTERNAL;

void sgen_queue_finalization_entry (MonoObject *obj) MONO_INTERNAL;
const char* sgen_generation_name (int generation) MONO_INTERNAL;

void sgen_collect_bridge_objects (int generation, ScanCopyContext ctx) MONO_INTERNAL;
void sgen_finalize_in_range (int generation, ScanCopyContext ctx) MONO_INTERNAL;
void sgen_null_link_in_range (int generation, gboolean before_finalization, ScanCopyContext ctx) MONO_INTERNAL;
void sgen_null_links_for_domain (MonoDomain *domain, int generation) MONO_INTERNAL;
void sgen_remove_finalizers_for_domain (MonoDomain *domain, int generation) MONO_INTERNAL;
void sgen_process_fin_stage_entries (void) MONO_INTERNAL;
void sgen_process_dislink_stage_entries (void) MONO_INTERNAL;
void sgen_register_disappearing_link (MonoObject *obj, void **link, gboolean track, gboolean in_gc) MONO_INTERNAL;

gboolean sgen_drain_gray_stack (int max_objs, ScanCopyContext ctx) MONO_INTERNAL;

enum {
	SPACE_NURSERY,
	SPACE_MAJOR,
	SPACE_LOS
};

void sgen_pin_object (void *object, SgenGrayQueue *queue) MONO_INTERNAL;
void sgen_parallel_pin_or_update (void **ptr, void *obj, MonoVTable *vt, SgenGrayQueue *queue) MONO_INTERNAL;
void sgen_set_pinned_from_failed_allocation (mword objsize) MONO_INTERNAL;

void sgen_ensure_free_space (size_t size) MONO_INTERNAL;
void sgen_perform_collection (size_t requested_size, int generation_to_collect, const char *reason, gboolean wait_to_finish) MONO_INTERNAL;
gboolean sgen_has_critical_method (void) MONO_INTERNAL;
gboolean sgen_is_critical_method (MonoMethod *method) MONO_INTERNAL;

/* STW */

typedef struct {
	int generation;
	const char *reason;
	gboolean is_overflow;
	SGEN_TV_DECLARE (total_time);
	SGEN_TV_DECLARE (stw_time);
	SGEN_TV_DECLARE (bridge_time);
} GGTimingInfo;

int sgen_stop_world (int generation) MONO_INTERNAL;
int sgen_restart_world (int generation, GGTimingInfo *timing) MONO_INTERNAL;

/* LOS */

typedef struct _LOSObject LOSObject;
struct _LOSObject {
	LOSObject *next;
	mword size; /* this is the object size, lowest bit used for pin/mark */
	guint8 *cardtable_mod_union; /* only used by the concurrent collector */
#if SIZEOF_VOID_P < 8
	mword dummy;		/* to align object to sizeof (double) */
#endif
	char data [MONO_ZERO_LEN_ARRAY];
};

#define ARRAY_OBJ_INDEX(ptr,array,elem_size) (((char*)(ptr) - ((char*)(array) + G_STRUCT_OFFSET (MonoArray, vector))) / (elem_size))

extern LOSObject *los_object_list;
extern mword los_memory_usage;

void sgen_los_free_object (LOSObject *obj) MONO_INTERNAL;
void* sgen_los_alloc_large_inner (MonoVTable *vtable, size_t size) MONO_INTERNAL;
void sgen_los_sweep (void) MONO_INTERNAL;
gboolean sgen_ptr_is_in_los (char *ptr, char **start) MONO_INTERNAL;
void sgen_los_iterate_objects (IterateObjectCallbackFunc cb, void *user_data) MONO_INTERNAL;
void sgen_los_iterate_live_block_ranges (sgen_cardtable_block_callback callback) MONO_INTERNAL;
void sgen_los_scan_card_table (gboolean mod_union, SgenGrayQueue *queue) MONO_INTERNAL;
void sgen_los_update_cardtable_mod_union (void) MONO_INTERNAL;
void sgen_major_collector_scan_card_table (SgenGrayQueue *queue) MONO_INTERNAL;
gboolean sgen_los_is_valid_object (char *object) MONO_INTERNAL;
gboolean mono_sgen_los_describe_pointer (char *ptr) MONO_INTERNAL;
LOSObject* sgen_los_header_for_object (char *data) MONO_INTERNAL;
mword sgen_los_object_size (LOSObject *obj) MONO_INTERNAL;
void sgen_los_pin_object (char *obj) MONO_INTERNAL;
void sgen_los_unpin_object (char *obj) MONO_INTERNAL;
gboolean sgen_los_object_is_pinned (char *obj) MONO_INTERNAL;


/* nursery allocator */

void sgen_clear_nursery_fragments (void) MONO_INTERNAL;
void sgen_nursery_allocator_prepare_for_pinning (void) MONO_INTERNAL;
void sgen_nursery_allocator_set_nursery_bounds (char *nursery_start, char *nursery_end) MONO_INTERNAL;
mword sgen_build_nursery_fragments (GCMemSection *nursery_section, void **start, int num_entries, SgenGrayQueue *unpin_queue) MONO_INTERNAL;
void sgen_init_nursery_allocator (void) MONO_INTERNAL;
void sgen_nursery_allocator_init_heavy_stats (void) MONO_INTERNAL;
void sgen_alloc_init_heavy_stats (void) MONO_INTERNAL;
char* sgen_nursery_alloc_get_upper_alloc_bound (void) MONO_INTERNAL;
void* sgen_nursery_alloc (size_t size) MONO_INTERNAL;
void* sgen_nursery_alloc_range (size_t size, size_t min_size, size_t *out_alloc_size) MONO_INTERNAL;
MonoVTable* sgen_get_array_fill_vtable (void) MONO_INTERNAL;
gboolean sgen_can_alloc_size (size_t size) MONO_INTERNAL;
void sgen_nursery_retire_region (void *address, ptrdiff_t size) MONO_INTERNAL;

void sgen_nursery_alloc_prepare_for_minor (void) MONO_INTERNAL;
void sgen_nursery_alloc_prepare_for_major (void) MONO_INTERNAL;

char* sgen_alloc_for_promotion (char *obj, size_t objsize, gboolean has_references) MONO_INTERNAL;
char* sgen_par_alloc_for_promotion (char *obj, size_t objsize, gboolean has_references) MONO_INTERNAL;

/* TLS Data */

extern MonoNativeTlsKey thread_info_key;

#ifdef HAVE_KW_THREAD
extern __thread SgenThreadInfo *sgen_thread_info;
extern __thread char *stack_end;
#endif

#ifdef HAVE_KW_THREAD
#define TLAB_ACCESS_INIT
#define IN_CRITICAL_REGION sgen_thread_info->in_critical_region
#else
#define TLAB_ACCESS_INIT	SgenThreadInfo *__thread_info__ = mono_native_tls_get_value (thread_info_key)
#define IN_CRITICAL_REGION (__thread_info__->in_critical_region)
#endif

#ifndef DISABLE_CRITICAL_REGION

#ifdef HAVE_KW_THREAD
#define IN_CRITICAL_REGION sgen_thread_info->in_critical_region
#else
#define IN_CRITICAL_REGION (__thread_info__->in_critical_region)
#endif

/* Enter must be visible before anything is done in the critical region. */
#define ENTER_CRITICAL_REGION do { mono_atomic_store_acquire (&IN_CRITICAL_REGION, 1); } while (0)

/* Exit must make sure all critical regions stores are visible before it signal the end of the region. 
 * We don't need to emit a full barrier since we
 */
#define EXIT_CRITICAL_REGION  do { mono_atomic_store_release (&IN_CRITICAL_REGION, 0); } while (0)

#endif

#ifdef HAVE_KW_THREAD
#define EMIT_TLS_ACCESS(mb,member,key)	do {	\
	mono_mb_emit_byte ((mb), MONO_CUSTOM_PREFIX);	\
	mono_mb_emit_byte ((mb), CEE_MONO_TLS);		\
	mono_mb_emit_i4 ((mb), (key));		\
	} while (0)
#else

#if defined(__APPLE__) || defined (HOST_WIN32)
#define EMIT_TLS_ACCESS(mb,member,key)	do {	\
	mono_mb_emit_byte ((mb), MONO_CUSTOM_PREFIX);	\
	mono_mb_emit_byte ((mb), CEE_MONO_TLS);		\
	mono_mb_emit_i4 ((mb), TLS_KEY_SGEN_THREAD_INFO);	\
	mono_mb_emit_icon ((mb), G_STRUCT_OFFSET (SgenThreadInfo, member));	\
	mono_mb_emit_byte ((mb), CEE_ADD);		\
	mono_mb_emit_byte ((mb), CEE_LDIND_I);		\
	} while (0)
#else
#define EMIT_TLS_ACCESS(mb,member,key)	do { g_error ("sgen is not supported when using --with-tls=pthread.\n"); } while (0)
#endif

#endif

/* Other globals */

extern GCMemSection *nursery_section;
extern int stat_major_gcs;
extern guint32 collect_before_allocs;
extern guint32 verify_before_allocs;
extern gboolean has_per_allocation_action;
extern int degraded_mode;
extern int default_nursery_size;
extern guint32 tlab_size;
extern NurseryClearPolicy nursery_clear_policy;
extern gboolean sgen_try_free_some_memory;

extern LOCK_DECLARE (gc_mutex);

extern int do_pin_stats;

/* Nursery helpers. */

static inline void
sgen_set_nursery_scan_start (char *p)
{
	int idx = (p - (char*)nursery_section->data) / SGEN_SCAN_START_SIZE;
	char *old = nursery_section->scan_starts [idx];
	if (!old || old > p)
		nursery_section->scan_starts [idx] = p;
}


/* Object Allocation */

typedef enum {
	ATYPE_NORMAL,
	ATYPE_VECTOR,
	ATYPE_SMALL,
	ATYPE_STRING,
	ATYPE_NUM
} SgenAllocatorType;

void sgen_init_tlab_info (SgenThreadInfo* info);
void sgen_clear_tlabs (void);
void sgen_set_use_managed_allocator (gboolean flag);
gboolean sgen_is_managed_allocator (MonoMethod *method);
gboolean sgen_has_managed_allocator (void);

/* Debug support */

void sgen_check_consistency (void);
void sgen_check_mod_union_consistency (void);
void sgen_check_major_refs (void);
void sgen_check_whole_heap (gboolean allow_missing_pinning);
void sgen_check_whole_heap_stw (void) MONO_INTERNAL;
void sgen_check_objref (char *obj);
void sgen_check_major_heap_marked (void) MONO_INTERNAL;
void sgen_check_nursery_objects_pinned (gboolean pinned) MONO_INTERNAL;

/* Write barrier support */

/*
 * This causes the compile to extend the liveness of 'v' till the call to dummy_use
 */
static inline void
sgen_dummy_use (gpointer v) {
#if defined(__GNUC__)
	__asm__ volatile ("" : "=r"(v) : "r"(v));
#elif defined(_MSC_VER)
	__asm {
		mov eax, v;
		and eax, eax;
	};
#else
#error "Implement sgen_dummy_use for your compiler"
#endif
}

/* Environment variable parsing */

#define MONO_GC_PARAMS_NAME	"MONO_GC_PARAMS"
#define MONO_GC_DEBUG_NAME	"MONO_GC_DEBUG"

gboolean sgen_parse_environment_string_extract_number (const char *str, glong *out) MONO_INTERNAL;
void sgen_env_var_error (const char *env_var, const char *fallback, const char *description_format, ...) MONO_INTERNAL;

/* Utilities */

void sgen_qsort (void *base, size_t nel, size_t width, int (*compar) (const void*, const void*)) MONO_INTERNAL;

#endif /* HAVE_SGEN_GC */

#endif /* __MONO_SGENGC_H__ */