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sgen-gc.c
5435 lines (4573 loc) · 164 KB
/
sgen-gc.c
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/*
* sgen-gc.c: Simple generational GC.
*
* Author:
* Paolo Molaro (lupus@ximian.com)
* Rodrigo Kumpera (kumpera@gmail.com)
*
* Copyright 2005-2011 Novell, Inc (http://www.novell.com)
* Copyright 2011 Xamarin Inc (http://www.xamarin.com)
*
* Thread start/stop adapted from Boehm's GC:
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996 by Silicon Graphics. All rights reserved.
* Copyright (c) 1998 by Fergus Henderson. All rights reserved.
* Copyright (c) 2000-2004 by Hewlett-Packard Company. All rights reserved.
* Copyright 2001-2003 Ximian, Inc
* Copyright 2003-2010 Novell, Inc.
* Copyright 2011 Xamarin, Inc.
* 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.
*
* Important: allocation provides always zeroed memory, having to do
* a memset after allocation is deadly for performance.
* Memory usage at startup is currently as follows:
* 64 KB pinned space
* 64 KB internal space
* size of nursery
* We should provide a small memory config with half the sizes
*
* We currently try to make as few mono assumptions as possible:
* 1) 2-word header with no GC pointers in it (first vtable, second to store the
* forwarding ptr)
* 2) gc descriptor is the second word in the vtable (first word in the class)
* 3) 8 byte alignment is the minimum and enough (not true for special structures (SIMD), FIXME)
* 4) there is a function to get an object's size and the number of
* elements in an array.
* 5) we know the special way bounds are allocated for complex arrays
* 6) we know about proxies and how to treat them when domains are unloaded
*
* Always try to keep stack usage to a minimum: no recursive behaviour
* and no large stack allocs.
*
* General description.
* Objects are initially allocated in a nursery using a fast bump-pointer technique.
* When the nursery is full we start a nursery collection: this is performed with a
* copying GC.
* When the old generation is full we start a copying GC of the old generation as well:
* this will be changed to mark&sweep with copying when fragmentation becomes to severe
* in the future. Maybe we'll even do both during the same collection like IMMIX.
*
* The things that complicate this description are:
* *) pinned objects: we can't move them so we need to keep track of them
* *) no precise info of the thread stacks and registers: we need to be able to
* quickly find the objects that may be referenced conservatively and pin them
* (this makes the first issues more important)
* *) large objects are too expensive to be dealt with using copying GC: we handle them
* with mark/sweep during major collections
* *) some objects need to not move even if they are small (interned strings, Type handles):
* we use mark/sweep for them, too: they are not allocated in the nursery, but inside
* PinnedChunks regions
*/
/*
* TODO:
*) we could have a function pointer in MonoClass to implement
customized write barriers for value types
*) investigate the stuff needed to advance a thread to a GC-safe
point (single-stepping, read from unmapped memory etc) and implement it.
This would enable us to inline allocations and write barriers, for example,
or at least parts of them, like the write barrier checks.
We may need this also for handling precise info on stacks, even simple things
as having uninitialized data on the stack and having to wait for the prolog
to zero it. Not an issue for the last frame that we scan conservatively.
We could always not trust the value in the slots anyway.
*) modify the jit to save info about references in stack locations:
this can be done just for locals as a start, so that at least
part of the stack is handled precisely.
*) test/fix endianess issues
*) Implement a card table as the write barrier instead of remembered
sets? Card tables are not easy to implement with our current
memory layout. We have several different kinds of major heap
objects: Small objects in regular blocks, small objects in pinned
chunks and LOS objects. If we just have a pointer we have no way
to tell which kind of object it points into, therefore we cannot
know where its card table is. The least we have to do to make
this happen is to get rid of write barriers for indirect stores.
(See next item)
*) Get rid of write barriers for indirect stores. We can do this by
telling the GC to wbarrier-register an object once we do an ldloca
or ldelema on it, and to unregister it once it's not used anymore
(it can only travel downwards on the stack). The problem with
unregistering is that it needs to happen eventually no matter
what, even if exceptions are thrown, the thread aborts, etc.
Rodrigo suggested that we could do only the registering part and
let the collector find out (pessimistically) when it's safe to
unregister, namely when the stack pointer of the thread that
registered the object is higher than it was when the registering
happened. This might make for a good first implementation to get
some data on performance.
*) Some sort of blacklist support? Blacklists is a concept from the
Boehm GC: if during a conservative scan we find pointers to an
area which we might use as heap, we mark that area as unusable, so
pointer retention by random pinning pointers is reduced.
*) experiment with max small object size (very small right now - 2kb,
because it's tied to the max freelist size)
*) add an option to mmap the whole heap in one chunk: it makes for many
simplifications in the checks (put the nursery at the top and just use a single
check for inclusion/exclusion): the issue this has is that on 32 bit systems it's
not flexible (too much of the address space may be used by default or we can't
increase the heap as needed) and we'd need a race-free mechanism to return memory
back to the system (mprotect(PROT_NONE) will still keep the memory allocated if it
was written to, munmap is needed, but the following mmap may not find the same segment
free...)
*) memzero the major fragments after restarting the world and optionally a smaller
chunk at a time
*) investigate having fragment zeroing threads
*) separate locks for finalization and other minor stuff to reduce
lock contention
*) try a different copying order to improve memory locality
*) a thread abort after a store but before the write barrier will
prevent the write barrier from executing
*) specialized dynamically generated markers/copiers
*) Dynamically adjust TLAB size to the number of threads. If we have
too many threads that do allocation, we might need smaller TLABs,
and we might get better performance with larger TLABs if we only
have a handful of threads. We could sum up the space left in all
assigned TLABs and if that's more than some percentage of the
nursery size, reduce the TLAB size.
*) Explore placing unreachable objects on unused nursery memory.
Instead of memset'ng a region to zero, place an int[] covering it.
A good place to start is add_nursery_frag. The tricky thing here is
placing those objects atomically outside of a collection.
*) Allocation should use asymmetric Dekker synchronization:
http://blogs.oracle.com/dave/resource/Asymmetric-Dekker-Synchronization.txt
This should help weak consistency archs.
*/
#include "config.h"
#ifdef HAVE_SGEN_GC
#ifdef __MACH__
#undef _XOPEN_SOURCE
#define _XOPEN_SOURCE
#define _DARWIN_C_SOURCE
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif
#ifdef HAVE_PTHREAD_NP_H
#include <pthread_np.h>
#endif
#ifdef HAVE_SEMAPHORE_H
#include <semaphore.h>
#endif
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <errno.h>
#include <assert.h>
#include "metadata/sgen-gc.h"
#include "metadata/metadata-internals.h"
#include "metadata/class-internals.h"
#include "metadata/gc-internal.h"
#include "metadata/object-internals.h"
#include "metadata/threads.h"
#include "metadata/sgen-cardtable.h"
#include "metadata/sgen-protocol.h"
#include "metadata/sgen-archdep.h"
#include "metadata/sgen-bridge.h"
#include "metadata/sgen-memory-governor.h"
#include "metadata/sgen-hash-table.h"
#include "metadata/mono-gc.h"
#include "metadata/method-builder.h"
#include "metadata/profiler-private.h"
#include "metadata/monitor.h"
#include "metadata/mempool-internals.h"
#include "metadata/marshal.h"
#include "metadata/runtime.h"
#include "metadata/sgen-cardtable.h"
#include "metadata/sgen-pinning.h"
#include "metadata/sgen-workers.h"
#include "metadata/sgen-layout-stats.h"
#include "utils/mono-mmap.h"
#include "utils/mono-time.h"
#include "utils/mono-semaphore.h"
#include "utils/mono-counters.h"
#include "utils/mono-proclib.h"
#include "utils/mono-memory-model.h"
#include "utils/mono-logger-internal.h"
#include "utils/dtrace.h"
#include <mono/utils/mono-logger-internal.h>
#include <mono/utils/memcheck.h>
#if defined(__MACH__)
#include "utils/mach-support.h"
#endif
#define OPDEF(a,b,c,d,e,f,g,h,i,j) \
a = i,
enum {
#include "mono/cil/opcode.def"
CEE_LAST
};
#undef OPDEF
#undef pthread_create
#undef pthread_join
#undef pthread_detach
/*
* ######################################################################
* ######## Types and constants used by the GC.
* ######################################################################
*/
/* 0 means not initialized, 1 is initialized, -1 means in progress */
static int gc_initialized = 0;
/* If set, check if we need to do something every X allocations */
gboolean has_per_allocation_action;
/* If set, do a heap check every X allocation */
guint32 verify_before_allocs = 0;
/* If set, do a minor collection before every X allocation */
guint32 collect_before_allocs = 0;
/* If set, do a whole heap check before each collection */
static gboolean whole_heap_check_before_collection = FALSE;
/* If set, do a heap consistency check before each minor collection */
static gboolean consistency_check_at_minor_collection = FALSE;
/* If set, do a mod union consistency check before each finishing collection pause */
static gboolean mod_union_consistency_check = FALSE;
/* If set, check whether mark bits are consistent after major collections */
static gboolean check_mark_bits_after_major_collection = FALSE;
/* If set, check that all nursery objects are pinned/not pinned, depending on context */
static gboolean check_nursery_objects_pinned = FALSE;
/* If set, do a few checks when the concurrent collector is used */
static gboolean do_concurrent_checks = FALSE;
/* If set, check that there are no references to the domain left at domain unload */
static gboolean xdomain_checks = FALSE;
/* If not null, dump the heap after each collection into this file */
static FILE *heap_dump_file = NULL;
/* If set, mark stacks conservatively, even if precise marking is possible */
static gboolean conservative_stack_mark = FALSE;
/* If set, do a plausibility check on the scan_starts before and after
each collection */
static gboolean do_scan_starts_check = FALSE;
/*
* If the major collector is concurrent and this is FALSE, we will
* never initiate a synchronous major collection, unless requested via
* GC.Collect().
*/
static gboolean allow_synchronous_major = TRUE;
static gboolean nursery_collection_is_parallel = FALSE;
static gboolean disable_minor_collections = FALSE;
static gboolean disable_major_collections = FALSE;
gboolean do_pin_stats = FALSE;
static gboolean do_verify_nursery = FALSE;
static gboolean do_dump_nursery_content = FALSE;
#ifdef HEAVY_STATISTICS
long long stat_objects_alloced_degraded = 0;
long long stat_bytes_alloced_degraded = 0;
long long stat_copy_object_called_nursery = 0;
long long stat_objects_copied_nursery = 0;
long long stat_copy_object_called_major = 0;
long long stat_objects_copied_major = 0;
long long stat_scan_object_called_nursery = 0;
long long stat_scan_object_called_major = 0;
long long stat_slots_allocated_in_vain;
long long stat_nursery_copy_object_failed_from_space = 0;
long long stat_nursery_copy_object_failed_forwarded = 0;
long long stat_nursery_copy_object_failed_pinned = 0;
long long stat_nursery_copy_object_failed_to_space = 0;
static int stat_wbarrier_add_to_global_remset = 0;
static int stat_wbarrier_set_field = 0;
static int stat_wbarrier_set_arrayref = 0;
static int stat_wbarrier_arrayref_copy = 0;
static int stat_wbarrier_generic_store = 0;
static int stat_wbarrier_generic_store_atomic = 0;
static int stat_wbarrier_set_root = 0;
static int stat_wbarrier_value_copy = 0;
static int stat_wbarrier_object_copy = 0;
#endif
static long long stat_pinned_objects = 0;
static long long time_minor_pre_collection_fragment_clear = 0;
static long long time_minor_pinning = 0;
static long long time_minor_scan_remsets = 0;
static long long time_minor_scan_pinned = 0;
static long long time_minor_scan_registered_roots = 0;
static long long time_minor_scan_thread_data = 0;
static long long time_minor_finish_gray_stack = 0;
static long long time_minor_fragment_creation = 0;
static long long time_major_pre_collection_fragment_clear = 0;
static long long time_major_pinning = 0;
static long long time_major_scan_pinned = 0;
static long long time_major_scan_registered_roots = 0;
static long long time_major_scan_thread_data = 0;
static long long time_major_scan_alloc_pinned = 0;
static long long time_major_scan_finalized = 0;
static long long time_major_scan_big_objects = 0;
static long long time_major_finish_gray_stack = 0;
static long long time_major_free_bigobjs = 0;
static long long time_major_los_sweep = 0;
static long long time_major_sweep = 0;
static long long time_major_fragment_creation = 0;
int gc_debug_level = 0;
FILE* gc_debug_file;
static MonoGCFinalizerCallbacks fin_callbacks;
/*
void
mono_gc_flush_info (void)
{
fflush (gc_debug_file);
}
*/
#define TV_DECLARE SGEN_TV_DECLARE
#define TV_GETTIME SGEN_TV_GETTIME
#define TV_ELAPSED SGEN_TV_ELAPSED
#define TV_ELAPSED_MS SGEN_TV_ELAPSED_MS
SGEN_TV_DECLARE (sgen_init_timestamp);
#define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
NurseryClearPolicy nursery_clear_policy = CLEAR_AT_TLAB_CREATION;
#define object_is_forwarded SGEN_OBJECT_IS_FORWARDED
#define object_is_pinned SGEN_OBJECT_IS_PINNED
#define pin_object SGEN_PIN_OBJECT
#define unpin_object SGEN_UNPIN_OBJECT
#define ptr_in_nursery sgen_ptr_in_nursery
#define LOAD_VTABLE SGEN_LOAD_VTABLE
static const char*
safe_name (void* obj)
{
MonoVTable *vt = (MonoVTable*)LOAD_VTABLE (obj);
return vt->klass->name;
}
#define safe_object_get_size sgen_safe_object_get_size
const char*
sgen_safe_name (void* obj)
{
return safe_name (obj);
}
/*
* ######################################################################
* ######## Global data.
* ######################################################################
*/
LOCK_DECLARE (gc_mutex);
gboolean sgen_try_free_some_memory;
#define SCAN_START_SIZE SGEN_SCAN_START_SIZE
static mword pagesize = 4096;
size_t degraded_mode = 0;
static mword bytes_pinned_from_failed_allocation = 0;
GCMemSection *nursery_section = NULL;
static mword lowest_heap_address = ~(mword)0;
static mword highest_heap_address = 0;
LOCK_DECLARE (sgen_interruption_mutex);
static LOCK_DECLARE (pin_queue_mutex);
#define LOCK_PIN_QUEUE mono_mutex_lock (&pin_queue_mutex)
#define UNLOCK_PIN_QUEUE mono_mutex_unlock (&pin_queue_mutex)
typedef struct _FinalizeReadyEntry FinalizeReadyEntry;
struct _FinalizeReadyEntry {
FinalizeReadyEntry *next;
void *object;
};
typedef struct _EphemeronLinkNode EphemeronLinkNode;
struct _EphemeronLinkNode {
EphemeronLinkNode *next;
char *array;
};
typedef struct {
void *key;
void *value;
} Ephemeron;
int current_collection_generation = -1;
volatile gboolean concurrent_collection_in_progress = FALSE;
/* objects that are ready to be finalized */
static FinalizeReadyEntry *fin_ready_list = NULL;
static FinalizeReadyEntry *critical_fin_list = NULL;
static EphemeronLinkNode *ephemeron_list;
/* registered roots: the key to the hash is the root start address */
/*
* Different kinds of roots are kept separate to speed up pin_from_roots () for example.
*/
SgenHashTable roots_hash [ROOT_TYPE_NUM] = {
SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), mono_aligned_addr_hash, NULL),
SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), mono_aligned_addr_hash, NULL),
SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), mono_aligned_addr_hash, NULL)
};
static mword roots_size = 0; /* amount of memory in the root set */
#define GC_ROOT_NUM 32
typedef struct {
int count; /* must be the first field */
void *objects [GC_ROOT_NUM];
int root_types [GC_ROOT_NUM];
uintptr_t extra_info [GC_ROOT_NUM];
} GCRootReport;
static void
notify_gc_roots (GCRootReport *report)
{
if (!report->count)
return;
mono_profiler_gc_roots (report->count, report->objects, report->root_types, report->extra_info);
report->count = 0;
}
static void
add_profile_gc_root (GCRootReport *report, void *object, int rtype, uintptr_t extra_info)
{
if (report->count == GC_ROOT_NUM)
notify_gc_roots (report);
report->objects [report->count] = object;
report->root_types [report->count] = rtype;
report->extra_info [report->count++] = (uintptr_t)((MonoVTable*)LOAD_VTABLE (object))->klass;
}
MonoNativeTlsKey thread_info_key;
#ifdef HAVE_KW_THREAD
__thread SgenThreadInfo *sgen_thread_info;
__thread char *stack_end;
#endif
/* The size of a TLAB */
/* The bigger the value, the less often we have to go to the slow path to allocate a new
* one, but the more space is wasted by threads not allocating much memory.
* FIXME: Tune this.
* FIXME: Make this self-tuning for each thread.
*/
guint32 tlab_size = (1024 * 4);
#define MAX_SMALL_OBJ_SIZE SGEN_MAX_SMALL_OBJ_SIZE
/* Functions supplied by the runtime to be called by the GC */
static MonoGCCallbacks gc_callbacks;
#define ALLOC_ALIGN SGEN_ALLOC_ALIGN
#define ALLOC_ALIGN_BITS SGEN_ALLOC_ALIGN_BITS
#define ALIGN_UP SGEN_ALIGN_UP
#define MOVED_OBJECTS_NUM 64
static void *moved_objects [MOVED_OBJECTS_NUM];
static int moved_objects_idx = 0;
/* Vtable of the objects used to fill out nursery fragments before a collection */
static MonoVTable *array_fill_vtable;
#ifdef SGEN_DEBUG_INTERNAL_ALLOC
MonoNativeThreadId main_gc_thread = NULL;
#endif
/*Object was pinned during the current collection*/
static mword objects_pinned;
/*
* ######################################################################
* ######## Macros and function declarations.
* ######################################################################
*/
inline static void*
align_pointer (void *ptr)
{
mword p = (mword)ptr;
p += sizeof (gpointer) - 1;
p &= ~ (sizeof (gpointer) - 1);
return (void*)p;
}
typedef SgenGrayQueue GrayQueue;
/* forward declarations */
static void scan_thread_data (void *start_nursery, void *end_nursery, gboolean precise, GrayQueue *queue);
static void scan_from_registered_roots (char *addr_start, char *addr_end, int root_type, ScanCopyContext ctx);
static void scan_finalizer_entries (FinalizeReadyEntry *list, ScanCopyContext ctx);
static void report_finalizer_roots (void);
static void report_registered_roots (void);
static void pin_from_roots (void *start_nursery, void *end_nursery, GrayQueue *queue);
static void finish_gray_stack (int generation, GrayQueue *queue);
void mono_gc_scan_for_specific_ref (MonoObject *key, gboolean precise);
static void init_stats (void);
static int mark_ephemerons_in_range (ScanCopyContext ctx);
static void clear_unreachable_ephemerons (ScanCopyContext ctx);
static void null_ephemerons_for_domain (MonoDomain *domain);
static gboolean major_update_or_finish_concurrent_collection (gboolean force_finish);
SgenObjectOperations current_object_ops;
SgenMajorCollector major_collector;
SgenMinorCollector sgen_minor_collector;
static GrayQueue gray_queue;
static SgenRemeberedSet remset;
/* The gray queue to use from the main collection thread. */
#define WORKERS_DISTRIBUTE_GRAY_QUEUE (&gray_queue)
/*
* The gray queue a worker job must use. If we're not parallel or
* concurrent, we use the main gray queue.
*/
static SgenGrayQueue*
sgen_workers_get_job_gray_queue (WorkerData *worker_data)
{
return worker_data ? &worker_data->private_gray_queue : WORKERS_DISTRIBUTE_GRAY_QUEUE;
}
static void
gray_queue_redirect (SgenGrayQueue *queue)
{
gboolean wake = FALSE;
for (;;) {
GrayQueueSection *section = sgen_gray_object_dequeue_section (queue);
if (!section)
break;
sgen_section_gray_queue_enqueue (queue->alloc_prepare_data, section);
wake = TRUE;
}
if (wake) {
g_assert (concurrent_collection_in_progress ||
(current_collection_generation == GENERATION_OLD && major_collector.is_parallel));
if (sgen_workers_have_started ()) {
sgen_workers_wake_up_all ();
} else {
if (concurrent_collection_in_progress)
g_assert (current_collection_generation == -1);
}
}
}
void
sgen_scan_area_with_callback (char *start, char *end, IterateObjectCallbackFunc callback, void *data, gboolean allow_flags)
{
while (start < end) {
size_t size;
char *obj;
if (!*(void**)start) {
start += sizeof (void*); /* should be ALLOC_ALIGN, really */
continue;
}
if (allow_flags) {
if (!(obj = SGEN_OBJECT_IS_FORWARDED (start)))
obj = start;
} else {
obj = start;
}
size = ALIGN_UP (safe_object_get_size ((MonoObject*)obj));
if ((MonoVTable*)SGEN_LOAD_VTABLE (obj) != array_fill_vtable)
callback (obj, size, data);
start += size;
}
}
static gboolean
need_remove_object_for_domain (char *start, MonoDomain *domain)
{
if (mono_object_domain (start) == domain) {
SGEN_LOG (4, "Need to cleanup object %p", start);
binary_protocol_cleanup (start, (gpointer)LOAD_VTABLE (start), safe_object_get_size ((MonoObject*)start));
return TRUE;
}
return FALSE;
}
static void
process_object_for_domain_clearing (char *start, MonoDomain *domain)
{
GCVTable *vt = (GCVTable*)LOAD_VTABLE (start);
if (vt->klass == mono_defaults.internal_thread_class)
g_assert (mono_object_domain (start) == mono_get_root_domain ());
/* The object could be a proxy for an object in the domain
we're deleting. */
#ifndef DISABLE_REMOTING
if (mono_defaults.real_proxy_class->supertypes && mono_class_has_parent_fast (vt->klass, mono_defaults.real_proxy_class)) {
MonoObject *server = ((MonoRealProxy*)start)->unwrapped_server;
/* The server could already have been zeroed out, so
we need to check for that, too. */
if (server && (!LOAD_VTABLE (server) || mono_object_domain (server) == domain)) {
SGEN_LOG (4, "Cleaning up remote pointer in %p to object %p", start, server);
((MonoRealProxy*)start)->unwrapped_server = NULL;
}
}
#endif
}
static gboolean
clear_domain_process_object (char *obj, MonoDomain *domain)
{
gboolean remove;
process_object_for_domain_clearing (obj, domain);
remove = need_remove_object_for_domain (obj, domain);
if (remove && ((MonoObject*)obj)->synchronisation) {
void **dislink = mono_monitor_get_object_monitor_weak_link ((MonoObject*)obj);
if (dislink)
sgen_register_disappearing_link (NULL, dislink, FALSE, TRUE);
}
return remove;
}
static void
clear_domain_process_minor_object_callback (char *obj, size_t size, MonoDomain *domain)
{
if (clear_domain_process_object (obj, domain))
memset (obj, 0, size);
}
static void
clear_domain_process_major_object_callback (char *obj, size_t size, MonoDomain *domain)
{
clear_domain_process_object (obj, domain);
}
static void
clear_domain_free_major_non_pinned_object_callback (char *obj, size_t size, MonoDomain *domain)
{
if (need_remove_object_for_domain (obj, domain))
major_collector.free_non_pinned_object (obj, size);
}
static void
clear_domain_free_major_pinned_object_callback (char *obj, size_t size, MonoDomain *domain)
{
if (need_remove_object_for_domain (obj, domain))
major_collector.free_pinned_object (obj, size);
}
/*
* When appdomains are unloaded we can easily remove objects that have finalizers,
* but all the others could still be present in random places on the heap.
* We need a sweep to get rid of them even though it's going to be costly
* with big heaps.
* The reason we need to remove them is because we access the vtable and class
* structures to know the object size and the reference bitmap: once the domain is
* unloaded the point to random memory.
*/
void
mono_gc_clear_domain (MonoDomain * domain)
{
LOSObject *bigobj, *prev;
int i;
LOCK_GC;
binary_protocol_domain_unload_begin (domain);
sgen_stop_world (0);
if (concurrent_collection_in_progress)
sgen_perform_collection (0, GENERATION_OLD, "clear domain", TRUE);
g_assert (!concurrent_collection_in_progress);
sgen_process_fin_stage_entries ();
sgen_process_dislink_stage_entries ();
sgen_clear_nursery_fragments ();
if (xdomain_checks && domain != mono_get_root_domain ()) {
sgen_scan_for_registered_roots_in_domain (domain, ROOT_TYPE_NORMAL);
sgen_scan_for_registered_roots_in_domain (domain, ROOT_TYPE_WBARRIER);
sgen_check_for_xdomain_refs ();
}
/*Ephemerons and dislinks must be processed before LOS since they might end up pointing
to memory returned to the OS.*/
null_ephemerons_for_domain (domain);
for (i = GENERATION_NURSERY; i < GENERATION_MAX; ++i)
sgen_null_links_for_domain (domain, i);
for (i = GENERATION_NURSERY; i < GENERATION_MAX; ++i)
sgen_remove_finalizers_for_domain (domain, i);
sgen_scan_area_with_callback (nursery_section->data, nursery_section->end_data,
(IterateObjectCallbackFunc)clear_domain_process_minor_object_callback, domain, FALSE);
/* We need two passes over major and large objects because
freeing such objects might give their memory back to the OS
(in the case of large objects) or obliterate its vtable
(pinned objects with major-copying or pinned and non-pinned
objects with major-mark&sweep), but we might need to
dereference a pointer from an object to another object if
the first object is a proxy. */
major_collector.iterate_objects (ITERATE_OBJECTS_SWEEP_ALL, (IterateObjectCallbackFunc)clear_domain_process_major_object_callback, domain);
for (bigobj = los_object_list; bigobj; bigobj = bigobj->next)
clear_domain_process_object (bigobj->data, domain);
prev = NULL;
for (bigobj = los_object_list; bigobj;) {
if (need_remove_object_for_domain (bigobj->data, domain)) {
LOSObject *to_free = bigobj;
if (prev)
prev->next = bigobj->next;
else
los_object_list = bigobj->next;
bigobj = bigobj->next;
SGEN_LOG (4, "Freeing large object %p", bigobj->data);
sgen_los_free_object (to_free);
continue;
}
prev = bigobj;
bigobj = bigobj->next;
}
major_collector.iterate_objects (ITERATE_OBJECTS_SWEEP_NON_PINNED, (IterateObjectCallbackFunc)clear_domain_free_major_non_pinned_object_callback, domain);
major_collector.iterate_objects (ITERATE_OBJECTS_SWEEP_PINNED, (IterateObjectCallbackFunc)clear_domain_free_major_pinned_object_callback, domain);
if (domain == mono_get_root_domain ()) {
if (G_UNLIKELY (do_pin_stats))
sgen_pin_stats_print_class_stats ();
sgen_object_layout_dump (stdout);
}
sgen_restart_world (0, NULL);
binary_protocol_domain_unload_end (domain);
UNLOCK_GC;
}
/*
* sgen_add_to_global_remset:
*
* The global remset contains locations which point into newspace after
* a minor collection. This can happen if the objects they point to are pinned.
*
* LOCKING: If called from a parallel collector, the global remset
* lock must be held. For serial collectors that is not necessary.
*/
void
sgen_add_to_global_remset (gpointer ptr, gpointer obj)
{
SGEN_ASSERT (5, sgen_ptr_in_nursery (obj), "Target pointer of global remset must be in the nursery");
HEAVY_STAT (++stat_wbarrier_add_to_global_remset);
if (!major_collector.is_concurrent) {
SGEN_ASSERT (5, current_collection_generation != -1, "Global remsets can only be added during collections");
} else {
if (current_collection_generation == -1)
SGEN_ASSERT (5, sgen_concurrent_collection_in_progress (), "Global remsets outside of collection pauses can only be added by the concurrent collector");
}
if (!object_is_pinned (obj))
SGEN_ASSERT (5, sgen_minor_collector.is_split || sgen_concurrent_collection_in_progress (), "Non-pinned objects can only remain in nursery if it is a split nursery");
else if (sgen_cement_lookup_or_register (obj))
return;
remset.record_pointer (ptr);
if (G_UNLIKELY (do_pin_stats))
sgen_pin_stats_register_global_remset (obj);
SGEN_LOG (8, "Adding global remset for %p", ptr);
binary_protocol_global_remset (ptr, obj, (gpointer)SGEN_LOAD_VTABLE (obj));
#ifdef ENABLE_DTRACE
if (G_UNLIKELY (MONO_GC_GLOBAL_REMSET_ADD_ENABLED ())) {
MonoVTable *vt = (MonoVTable*)LOAD_VTABLE (obj);
MONO_GC_GLOBAL_REMSET_ADD ((mword)ptr, (mword)obj, sgen_safe_object_get_size (obj),
vt->klass->name_space, vt->klass->name);
}
#endif
}
/*
* sgen_drain_gray_stack:
*
* Scan objects in the gray stack until the stack is empty. This should be called
* frequently after each object is copied, to achieve better locality and cache
* usage.
*/
gboolean
sgen_drain_gray_stack (int max_objs, ScanCopyContext ctx)
{
char *obj;
ScanObjectFunc scan_func = ctx.scan_func;
GrayQueue *queue = ctx.queue;
if (max_objs == -1) {
for (;;) {
GRAY_OBJECT_DEQUEUE (queue, &obj);
if (!obj)
return TRUE;
SGEN_LOG (9, "Precise gray object scan %p (%s)", obj, safe_name (obj));
scan_func (obj, queue);
}
} else {
int i;
do {
for (i = 0; i != max_objs; ++i) {
GRAY_OBJECT_DEQUEUE (queue, &obj);
if (!obj)
return TRUE;
SGEN_LOG (9, "Precise gray object scan %p (%s)", obj, safe_name (obj));
scan_func (obj, queue);
}
} while (max_objs < 0);
return FALSE;
}
}
/*
* Addresses in the pin queue are already sorted. This function finds
* the object header for each address and pins the object. The
* addresses must be inside the nursery section. The (start of the)
* address array is overwritten with the addresses of the actually
* pinned objects. Return the number of pinned objects.
*/
static int
pin_objects_from_nursery_pin_queue (ScanCopyContext ctx)
{
GCMemSection *section = nursery_section;
void **start = section->pin_queue_start;
void **end = start + section->pin_queue_num_entries;
void *start_nursery = section->data;
void *end_nursery = section->next_data;
void *last = NULL;
int count = 0;
void *search_start;
void *addr;
void *pinning_front = start_nursery;
size_t idx;
void **definitely_pinned = start;
ScanObjectFunc scan_func = ctx.scan_func;
SgenGrayQueue *queue = ctx.queue;
sgen_nursery_allocator_prepare_for_pinning ();
while (start < end) {
void *obj_to_pin = NULL;
size_t obj_to_pin_size = 0;
addr = *start;
SGEN_ASSERT (0, addr >= start_nursery && addr < end_nursery, "Potential pinning address out of range");
SGEN_ASSERT (0, addr >= last, "Pin queue not sorted");
if (addr == last) {
++start;
continue;
}
SGEN_LOG (5, "Considering pinning addr %p", addr);
/* We've already processed everything up to pinning_front. */
if (addr < pinning_front) {
start++;
continue;
}
/*
* Find the closest scan start <= addr. We might search backward in the
* scan_starts array because entries might be NULL. In the worst case we
* start at start_nursery.
*/
idx = ((char*)addr - (char*)section->data) / SCAN_START_SIZE;
SGEN_ASSERT (0, idx < section->num_scan_start, "Scan start index out of range");
search_start = (void*)section->scan_starts [idx];
if (!search_start || search_start > addr) {
while (idx) {
--idx;
search_start = section->scan_starts [idx];
if (search_start && search_start <= addr)
break;
}
if (!search_start || search_start > addr)
search_start = start_nursery;
}
/*
* If the pinning front is closer than the scan start we found, start
* searching at the front.
*/
if (search_start < pinning_front)
search_start = pinning_front;
/*
* Now addr should be in an object a short distance from search_start.
*
* search_start must point to zeroed mem or point to an object.
*/
do {
size_t obj_size;
/* Skip zeros. */
if (!*(void**)search_start) {
search_start = (void*)ALIGN_UP ((mword)search_start + sizeof (gpointer));
/* The loop condition makes sure we don't overrun addr. */
continue;
}
obj_size = ALIGN_UP (safe_object_get_size ((MonoObject*)search_start));
if (addr >= search_start && (char*)addr < (char*)search_start + obj_size) {
/* This is the object we're looking for. */
obj_to_pin = search_start;
obj_to_pin_size = obj_size;
break;
}
/* Skip to the next object */
search_start = (void*)((char*)search_start + obj_size);
} while (search_start <= addr);
/* We've searched past the address we were looking for. */
if (!obj_to_pin) {
pinning_front = search_start;
goto next_pin_queue_entry;
}
/*