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jerryscript/jerry-core/ecma/base/ecma-gc.c
T
Zoltan Herczeg 5c852ab6fb Optimize LCache operation. 
The cache stores only real properties now, because storing NULLs has
little benefit according to tests. Since only real properties are
stored now, there is no need to create real references to objects
and property names, which reduces the keeping of dead objects after
garbage collection.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com
2016-06-02 03:56:36 -07:00

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18 KiB
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/* Copyright 2014-2016 Samsung Electronics Co., Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Garbage collector implementation
*/
#include "ecma-alloc.h"
#include "ecma-globals.h"
#include "ecma-gc.h"
#include "ecma-helpers.h"
#include "ecma-lcache.h"
#include "ecma-property-hashmap.h"
#include "jrt.h"
#include "jrt-libc-includes.h"
#include "jrt-bit-fields.h"
#include "re-compiler.h"
#include "vm-defines.h"
#include "vm-stack.h"
#define JERRY_INTERNAL
#include "jerry-internal.h"
/* TODO: Extract GC to a separate component */
/** \addtogroup ecma ECMA
* @{
*
* \addtogroup ecmagc Garbage collector
* @{
*/
/**
* An object's GC color
*
* Tri-color marking:
* WHITE_GRAY, unvisited -> WHITE // not referenced by a live object or the reference not found yet
* WHITE_GRAY, visited -> GRAY // referenced by some live object
* BLACK -> BLACK // all referenced objects are gray or black
*/
typedef enum
{
ECMA_GC_COLOR_WHITE_GRAY, /**< white or gray */
ECMA_GC_COLOR_BLACK, /**< black */
ECMA_GC_COLOR__COUNT /**< number of colors */
} ecma_gc_color_t;
/**
* List of marked (visited during current GC session) and umarked objects
*/
static ecma_object_t *ecma_gc_objects_lists[ECMA_GC_COLOR__COUNT];
/**
* Current state of an object's visited flag that indicates whether the object is in visited state:
* visited_field | visited_flip_flag | real_value
* false | false | false
* false | true | true
* true | false | true
* true | true | false
*/
static bool ecma_gc_visited_flip_flag = false;
/**
* Number of currently allocated objects
*/
static size_t ecma_gc_objects_number = 0;
/**
* Number of newly allocated objects since last GC session
*/
static size_t ecma_gc_new_objects_since_last_gc = 0;
static void ecma_gc_mark (ecma_object_t *object_p);
static void ecma_gc_sweep (ecma_object_t *object_p);
/**
* Get next object in list of objects with same generation.
*/
static inline ecma_object_t *
ecma_gc_get_object_next (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p != NULL);
return ECMA_GET_POINTER (ecma_object_t, object_p->gc_next_cp);
} /* ecma_gc_get_object_next */
/**
* Set next object in list of objects with same generation.
*/
static inline void
ecma_gc_set_object_next (ecma_object_t *object_p, /**< object */
ecma_object_t *next_object_p) /**< next object */
{
JERRY_ASSERT (object_p != NULL);
ECMA_SET_POINTER (object_p->gc_next_cp, next_object_p);
} /* ecma_gc_set_object_next */
/**
* Get visited flag of the object.
*/
static inline bool
ecma_gc_is_object_visited (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p != NULL);
bool flag_value = (object_p->type_flags_refs & ECMA_OBJECT_FLAG_GC_VISITED) != 0;
return flag_value != ecma_gc_visited_flip_flag;
} /* ecma_gc_is_object_visited */
/**
* Set visited flag of the object.
*/
static inline void
ecma_gc_set_object_visited (ecma_object_t *object_p, /**< object */
bool is_visited) /**< flag value */
{
JERRY_ASSERT (object_p != NULL);
if (is_visited != ecma_gc_visited_flip_flag)
{
object_p->type_flags_refs = (uint16_t) (object_p->type_flags_refs | ECMA_OBJECT_FLAG_GC_VISITED);
}
else
{
object_p->type_flags_refs = (uint16_t) (object_p->type_flags_refs & ~ECMA_OBJECT_FLAG_GC_VISITED);
}
} /* ecma_gc_set_object_visited */
/**
* Initialize GC information for the object
*/
inline void
ecma_init_gc_info (ecma_object_t *object_p) /**< object */
{
ecma_gc_objects_number++;
ecma_gc_new_objects_since_last_gc++;
JERRY_ASSERT (ecma_gc_new_objects_since_last_gc <= ecma_gc_objects_number);
JERRY_ASSERT (object_p->type_flags_refs < ECMA_OBJECT_REF_ONE);
object_p->type_flags_refs = (uint16_t) (object_p->type_flags_refs | ECMA_OBJECT_REF_ONE);
ecma_gc_set_object_next (object_p, ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY]);
ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY] = object_p;
/* Should be set to false at the beginning of garbage collection */
ecma_gc_set_object_visited (object_p, false);
} /* ecma_init_gc_info */
/**
* Increase reference counter of an object
*/
void
ecma_ref_object (ecma_object_t *object_p) /**< object */
{
if (object_p->type_flags_refs < ECMA_OBJECT_MAX_REF)
{
object_p->type_flags_refs = (uint16_t) (object_p->type_flags_refs + ECMA_OBJECT_REF_ONE);
}
else
{
jerry_fatal (ERR_REF_COUNT_LIMIT);
}
} /* ecma_ref_object */
/**
* Decrease reference counter of an object
*/
void
ecma_deref_object (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p->type_flags_refs >= ECMA_OBJECT_REF_ONE);
object_p->type_flags_refs = (uint16_t) (object_p->type_flags_refs - ECMA_OBJECT_REF_ONE);
} /* ecma_deref_object */
/**
* Initialize garbage collector
*/
void
ecma_gc_init (void)
{
ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY] = NULL;
ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK] = NULL;
ecma_gc_visited_flip_flag = false;
ecma_gc_objects_number = 0;
ecma_gc_new_objects_since_last_gc = 0;
} /* ecma_gc_init */
/**
* Mark referenced object from property
*/
static void
ecma_gc_mark_property (ecma_property_t *property_p) /**< property */
{
switch (ECMA_PROPERTY_GET_TYPE (property_p))
{
case ECMA_PROPERTY_TYPE_NAMEDDATA:
{
ecma_value_t value = ecma_get_named_data_property_value (property_p);
if (ecma_is_value_object (value))
{
ecma_object_t *value_obj_p = ecma_get_object_from_value (value);
ecma_gc_set_object_visited (value_obj_p, true);
}
break;
}
case ECMA_PROPERTY_TYPE_NAMEDACCESSOR:
{
ecma_object_t *getter_obj_p = ecma_get_named_accessor_property_getter (property_p);
ecma_object_t *setter_obj_p = ecma_get_named_accessor_property_setter (property_p);
if (getter_obj_p != NULL)
{
ecma_gc_set_object_visited (getter_obj_p, true);
}
if (setter_obj_p != NULL)
{
ecma_gc_set_object_visited (setter_obj_p, true);
}
break;
}
case ECMA_PROPERTY_TYPE_INTERNAL:
{
uint32_t property_value = ECMA_PROPERTY_VALUE_PTR (property_p)->value;
switch (ECMA_PROPERTY_GET_INTERNAL_PROPERTY_TYPE (property_p))
{
case ECMA_INTERNAL_PROPERTY_ECMA_VALUE: /* an ecma_value_t except object */
case ECMA_INTERNAL_PROPERTY_DATE_FLOAT: /* pointer to a ecma_number_t */
case ECMA_INTERNAL_PROPERTY_CLASS: /* an enum */
case ECMA_INTERNAL_PROPERTY_CODE_BYTECODE: /* pointer to a bytecode array */
case ECMA_INTERNAL_PROPERTY_REGEXP_BYTECODE: /* pointer to a regexp bytecode array */
case ECMA_INTERNAL_PROPERTY_NATIVE_CODE: /* an external pointer */
case ECMA_INTERNAL_PROPERTY_NATIVE_HANDLE: /* an external pointer */
case ECMA_INTERNAL_PROPERTY_FREE_CALLBACK: /* an object's native free callback */
case ECMA_INTERNAL_PROPERTY_BUILT_IN_ID: /* an integer */
case ECMA_INTERNAL_PROPERTY_BUILT_IN_ROUTINE_DESC: /* an integer */
case ECMA_INTERNAL_PROPERTY_NON_INSTANTIATED_BUILT_IN_MASK_0_31: /* an integer (bit-mask) */
case ECMA_INTERNAL_PROPERTY_NON_INSTANTIATED_BUILT_IN_MASK_32_63: /* an integer (bit-mask) */
{
break;
}
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_BOUND_THIS: /* an ecma value */
{
if (ecma_is_value_object (property_value))
{
ecma_object_t *obj_p = ecma_get_object_from_value (property_value);
ecma_gc_set_object_visited (obj_p, true);
}
break;
}
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_BOUND_ARGS: /* a collection of ecma values */
{
ecma_collection_header_t *bound_arg_list_p = ECMA_GET_INTERNAL_VALUE_POINTER (ecma_collection_header_t,
property_value);
ecma_collection_iterator_t bound_args_iterator;
ecma_collection_iterator_init (&bound_args_iterator, bound_arg_list_p);
for (ecma_length_t i = 0; i < bound_arg_list_p->unit_number; i++)
{
bool is_moved = ecma_collection_iterator_next (&bound_args_iterator);
JERRY_ASSERT (is_moved);
if (ecma_is_value_object (*bound_args_iterator.current_value_p))
{
ecma_object_t *obj_p = ecma_get_object_from_value (*bound_args_iterator.current_value_p);
ecma_gc_set_object_visited (obj_p, true);
}
}
break;
}
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_TARGET_FUNCTION: /* an object */
case ECMA_INTERNAL_PROPERTY_SCOPE: /* a lexical environment */
case ECMA_INTERNAL_PROPERTY_PARAMETERS_MAP: /* an object */
{
ecma_object_t *obj_p = ECMA_GET_INTERNAL_VALUE_POINTER (ecma_object_t, property_value);
ecma_gc_set_object_visited (obj_p, true);
break;
}
case ECMA_INTERNAL_PROPERTY__COUNT: /* not a real internal property type,
* but number of the real internal property types */
{
JERRY_UNREACHABLE ();
break;
}
}
break;
}
default:
{
JERRY_UNREACHABLE ();
break;
}
}
} /* ecma_gc_mark_property */
/**
* Mark objects as visited starting from specified object as root
*/
void
ecma_gc_mark (ecma_object_t *object_p) /**< object to mark from */
{
JERRY_ASSERT (object_p != NULL);
JERRY_ASSERT (ecma_gc_is_object_visited (object_p));
bool traverse_properties = true;
if (ecma_is_lexical_environment (object_p))
{
ecma_object_t *lex_env_p = ecma_get_lex_env_outer_reference (object_p);
if (lex_env_p != NULL)
{
ecma_gc_set_object_visited (lex_env_p, true);
}
if (ecma_get_lex_env_type (object_p) != ECMA_LEXICAL_ENVIRONMENT_DECLARATIVE)
{
ecma_object_t *binding_object_p = ecma_get_lex_env_binding_object (object_p);
ecma_gc_set_object_visited (binding_object_p, true);
traverse_properties = false;
}
}
else
{
ecma_object_t *proto_p = ecma_get_object_prototype (object_p);
if (proto_p != NULL)
{
ecma_gc_set_object_visited (proto_p, true);
}
}
if (traverse_properties)
{
ecma_property_header_t *prop_iter_p = ecma_get_property_list (object_p);
if (prop_iter_p != NULL
&& ECMA_PROPERTY_GET_TYPE (prop_iter_p->types + 0) == ECMA_PROPERTY_TYPE_HASHMAP)
{
prop_iter_p = ECMA_GET_POINTER (ecma_property_header_t,
prop_iter_p->next_property_cp);
}
while (prop_iter_p != NULL)
{
JERRY_ASSERT (ECMA_PROPERTY_IS_PROPERTY_PAIR (prop_iter_p));
if (prop_iter_p->types[0].type_and_flags != ECMA_PROPERTY_TYPE_DELETED)
{
ecma_gc_mark_property (prop_iter_p->types + 0);
}
if (prop_iter_p->types[1].type_and_flags != ECMA_PROPERTY_TYPE_DELETED)
{
ecma_gc_mark_property (prop_iter_p->types + 1);
}
prop_iter_p = ECMA_GET_POINTER (ecma_property_header_t,
prop_iter_p->next_property_cp);
}
}
} /* ecma_gc_mark */
/**
* Free specified object
*/
void
ecma_gc_sweep (ecma_object_t *object_p) /**< object to free */
{
JERRY_ASSERT (object_p != NULL
&& !ecma_gc_is_object_visited (object_p)
&& object_p->type_flags_refs < ECMA_OBJECT_REF_ONE);
if (!ecma_is_lexical_environment (object_p))
{
/* if the object provides free callback, invoke it with handle stored in the object */
ecma_external_pointer_t freecb_p;
ecma_external_pointer_t native_p;
bool is_retrieved = ecma_get_external_pointer_value (object_p,
ECMA_INTERNAL_PROPERTY_FREE_CALLBACK,
&freecb_p);
if (is_retrieved)
{
is_retrieved = ecma_get_external_pointer_value (object_p,
ECMA_INTERNAL_PROPERTY_NATIVE_HANDLE,
&native_p);
JERRY_ASSERT (is_retrieved);
jerry_dispatch_object_free_callback (freecb_p, native_p);
}
}
if (!ecma_is_lexical_environment (object_p)
|| ecma_get_lex_env_type (object_p) == ECMA_LEXICAL_ENVIRONMENT_DECLARATIVE)
{
ecma_property_header_t *prop_iter_p = ecma_get_property_list (object_p);
if (prop_iter_p != NULL
&& ECMA_PROPERTY_GET_TYPE (prop_iter_p->types + 0) == ECMA_PROPERTY_TYPE_HASHMAP)
{
ecma_property_hashmap_free (object_p);
prop_iter_p = ecma_get_property_list (object_p);
}
while (prop_iter_p != NULL)
{
JERRY_ASSERT (ECMA_PROPERTY_IS_PROPERTY_PAIR (prop_iter_p));
/* Both cannot be deleted. */
JERRY_ASSERT (prop_iter_p->types[0].type_and_flags != ECMA_PROPERTY_TYPE_DELETED
|| prop_iter_p->types[1].type_and_flags != ECMA_PROPERTY_TYPE_DELETED);
ecma_property_pair_t *prop_pair_p = (ecma_property_pair_t *) prop_iter_p;
for (int i = 0; i < ECMA_PROPERTY_PAIR_ITEM_COUNT; i++)
{
if (prop_iter_p->types[i].type_and_flags != ECMA_PROPERTY_TYPE_DELETED)
{
ecma_string_t *name_p = ECMA_GET_POINTER (ecma_string_t, prop_pair_p->names_cp[i]);
ecma_free_property (object_p, name_p, prop_iter_p->types + i);
if (name_p != NULL)
{
ecma_deref_ecma_string (name_p);
}
}
}
/* Both must be deleted. */
JERRY_ASSERT (prop_iter_p->types[0].type_and_flags == ECMA_PROPERTY_TYPE_DELETED
&& prop_iter_p->types[1].type_and_flags == ECMA_PROPERTY_TYPE_DELETED);
prop_iter_p = ECMA_GET_POINTER (ecma_property_header_t,
prop_iter_p->next_property_cp);
ecma_dealloc_property_pair (prop_pair_p);
}
}
JERRY_ASSERT (ecma_gc_objects_number > 0);
ecma_gc_objects_number--;
ecma_dealloc_object (object_p);
} /* ecma_gc_sweep */
/**
* Run garbage collecting
*/
void
ecma_gc_run (void)
{
ecma_gc_new_objects_since_last_gc = 0;
JERRY_ASSERT (ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK] == NULL);
/* if some object is referenced from stack or globals (i.e. it is root), mark it */
for (ecma_object_t *obj_iter_p = ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY];
obj_iter_p != NULL;
obj_iter_p = ecma_gc_get_object_next (obj_iter_p))
{
JERRY_ASSERT (!ecma_gc_is_object_visited (obj_iter_p));
if (obj_iter_p->type_flags_refs >= ECMA_OBJECT_REF_ONE)
{
ecma_gc_set_object_visited (obj_iter_p, true);
}
}
bool marked_anything_during_current_iteration = false;
do
{
marked_anything_during_current_iteration = false;
for (ecma_object_t *obj_iter_p = ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY], *obj_prev_p = NULL, *obj_next_p;
obj_iter_p != NULL;
obj_iter_p = obj_next_p)
{
obj_next_p = ecma_gc_get_object_next (obj_iter_p);
if (ecma_gc_is_object_visited (obj_iter_p))
{
/* Moving the object to list of marked objects */
ecma_gc_set_object_next (obj_iter_p, ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK]);
ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK] = obj_iter_p;
if (likely (obj_prev_p != NULL))
{
JERRY_ASSERT (ecma_gc_get_object_next (obj_prev_p) == obj_iter_p);
ecma_gc_set_object_next (obj_prev_p, obj_next_p);
}
else
{
ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY] = obj_next_p;
}
ecma_gc_mark (obj_iter_p);
marked_anything_during_current_iteration = true;
}
else
{
obj_prev_p = obj_iter_p;
}
}
}
while (marked_anything_during_current_iteration);
/* Sweeping objects that are currently unmarked */
for (ecma_object_t *obj_iter_p = ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY], *obj_next_p;
obj_iter_p != NULL;
obj_iter_p = obj_next_p)
{
obj_next_p = ecma_gc_get_object_next (obj_iter_p);
JERRY_ASSERT (!ecma_gc_is_object_visited (obj_iter_p));
ecma_gc_sweep (obj_iter_p);
}
/* Unmarking all objects */
ecma_gc_objects_lists[ECMA_GC_COLOR_WHITE_GRAY] = ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK];
ecma_gc_objects_lists[ECMA_GC_COLOR_BLACK] = NULL;
ecma_gc_visited_flip_flag = !ecma_gc_visited_flip_flag;
#ifndef CONFIG_ECMA_COMPACT_PROFILE_DISABLE_REGEXP_BUILTIN
/* Free RegExp bytecodes stored in cache */
re_cache_gc_run ();
#endif /* !CONFIG_ECMA_COMPACT_PROFILE_DISABLE_REGEXP_BUILTIN */
} /* ecma_gc_run */
/**
* Try to free some memory (depending on severity).
*/
void
ecma_try_to_give_back_some_memory (jmem_try_give_memory_back_severity_t severity) /**< severity of
* the request */
{
if (severity == JMEM_TRY_GIVE_MEMORY_BACK_SEVERITY_LOW)
{
/*
* If there is enough newly allocated objects since last GC, probably it is worthwhile to start GC now.
* Otherwise, probability to free sufficient space is considered to be low.
*/
if (ecma_gc_new_objects_since_last_gc * CONFIG_ECMA_GC_NEW_OBJECTS_SHARE_TO_START_GC > ecma_gc_objects_number)
{
ecma_gc_run ();
}
}
else
{
JERRY_ASSERT (severity == JMEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
/* Freeing as much memory as we currently can */
ecma_gc_run ();
}
} /* ecma_try_to_give_back_some_memory */
/**
* @}
* @}
*/
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