Ruben Ayrapetyan 4667d3078b Introduce GC start heuristics on low-severity try-give-memory-back requests.
JerryScript-DCO-1.0-Signed-off-by: Ruben Ayrapetyan r.ayrapetyan@samsung.com
2015-08-17 20:10:26 +03:00

569 lines
18 KiB
C++

/* Copyright 2014-2015 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.
*/
/** \addtogroup ecma ECMA
* @{
*
* \addtogroup ecmagc Garbage collector
* @{
*/
/**
* Garbage collector implementation
*/
#include "ecma-alloc.h"
#include "ecma-globals.h"
#include "ecma-gc.h"
#include "ecma-helpers.h"
#include "ecma-lcache.h"
#include "jrt.h"
#include "jrt-libc-includes.h"
#include "jrt-bit-fields.h"
#include "vm-stack.h"
#define JERRY_INTERNAL
#include "jerry-internal.h"
/**
* TODO:
* Extract GC to a separate component
*/
/**
* 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 GC reference counter of the object.
*/
static uint32_t
ecma_gc_get_object_refs (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p != NULL);
return (uint32_t) jrt_extract_bit_field (object_p->container,
ECMA_OBJECT_GC_REFS_POS,
ECMA_OBJECT_GC_REFS_WIDTH);
} /* ecma_gc_get_object_refs */
/**
* Set GC reference counter of the object.
*/
static void
ecma_gc_set_object_refs (ecma_object_t *object_p, /**< object */
uint32_t refs) /**< new reference counter */
{
JERRY_ASSERT (object_p != NULL);
object_p->container = jrt_set_bit_field_value (object_p->container,
refs,
ECMA_OBJECT_GC_REFS_POS,
ECMA_OBJECT_GC_REFS_WIDTH);
} /* ecma_gc_set_object_refs */
/**
* Get next object in list of objects with same generation.
*/
static ecma_object_t*
ecma_gc_get_object_next (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p != NULL);
JERRY_ASSERT (sizeof (uintptr_t) * JERRY_BITSINBYTE >= ECMA_OBJECT_GC_NEXT_CP_WIDTH);
uintptr_t next_cp = (uintptr_t) jrt_extract_bit_field (object_p->container,
ECMA_OBJECT_GC_NEXT_CP_POS,
ECMA_OBJECT_GC_NEXT_CP_WIDTH);
return ECMA_GET_POINTER (ecma_object_t,
next_cp);
} /* ecma_gc_get_object_next */
/**
* Set next object in list of objects with same generation.
*/
static 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);
uintptr_t next_cp;
ECMA_SET_POINTER (next_cp, next_object_p);
JERRY_ASSERT (sizeof (uintptr_t) * JERRY_BITSINBYTE >= ECMA_OBJECT_GC_NEXT_CP_WIDTH);
object_p->container = jrt_set_bit_field_value (object_p->container,
next_cp,
ECMA_OBJECT_GC_NEXT_CP_POS,
ECMA_OBJECT_GC_NEXT_CP_WIDTH);
} /* ecma_gc_set_object_next */
/**
* Get visited flag of the object.
*/
static bool
ecma_gc_is_object_visited (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (object_p != NULL);
bool flag_value = (bool) jrt_extract_bit_field (object_p->container,
ECMA_OBJECT_GC_VISITED_POS,
ECMA_OBJECT_GC_VISITED_WIDTH);
return (flag_value != ecma_gc_visited_flip_flag);
} /* ecma_gc_is_object_visited */
/**
* Set visited flag of the object.
*/
static void
ecma_gc_set_object_visited (ecma_object_t *object_p, /**< object */
bool is_visited) /**< flag value */
{
JERRY_ASSERT (object_p != NULL);
if (ecma_gc_visited_flip_flag)
{
is_visited = !is_visited;
}
object_p->container = jrt_set_bit_field_value (object_p->container,
is_visited,
ECMA_OBJECT_GC_VISITED_POS,
ECMA_OBJECT_GC_VISITED_WIDTH);
} /* ecma_gc_set_object_visited */
/**
* Initialize GC information for the object
*/
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);
ecma_gc_set_object_refs (object_p, 1);
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 */
{
ecma_gc_set_object_refs (object_p, ecma_gc_get_object_refs (object_p) + 1);
} /* ecma_ref_object */
/**
* Decrease reference counter of an object
*/
void
ecma_deref_object (ecma_object_t *object_p) /**< object */
{
JERRY_ASSERT (ecma_gc_get_object_refs (object_p) > 0);
ecma_gc_set_object_refs (object_p, ecma_gc_get_object_refs (object_p) - 1);
} /* 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_init */
/**
* 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_OBJECTBOUND)
{
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)
{
for (ecma_property_t *property_p = ecma_get_property_list (object_p), *next_property_p;
property_p != NULL;
property_p = next_property_p)
{
next_property_p = ECMA_GET_POINTER (ecma_property_t,
property_p->next_property_p);
switch ((ecma_property_type_t) property_p->type)
{
case ECMA_PROPERTY_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_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_INTERNAL:
{
ecma_internal_property_id_t property_id = (ecma_internal_property_id_t) property_p->u.internal_property.type;
uint32_t property_value = property_p->u.internal_property.value;
switch (property_id)
{
case ECMA_INTERNAL_PROPERTY_NUMBER_INDEXED_ARRAY_VALUES: /* a collection of ecma-values */
case ECMA_INTERNAL_PROPERTY_STRING_INDEXED_ARRAY_VALUES: /* a collection of ecma-values */
{
JERRY_UNIMPLEMENTED ("Indexed array storage is not implemented yet.");
}
case ECMA_INTERNAL_PROPERTY_PROTOTYPE: /* the property's value is located in ecma_object_t
(see above in the routine) */
case ECMA_INTERNAL_PROPERTY_EXTENSIBLE: /* the property's value is located in ecma_object_t
(see above in the routine) */
case ECMA_INTERNAL_PROPERTY__COUNT: /* not a real internal property type,
* but number of the real internal property types */
{
JERRY_UNREACHABLE ();
}
case ECMA_INTERNAL_PROPERTY_FORMAL_PARAMETERS: /* a collection of strings */
case ECMA_INTERNAL_PROPERTY_PRIMITIVE_STRING_VALUE: /* compressed pointer to a ecma_string_t */
case ECMA_INTERNAL_PROPERTY_PRIMITIVE_NUMBER_VALUE: /* compressed pointer to a ecma_number_t */
case ECMA_INTERNAL_PROPERTY_PRIMITIVE_BOOLEAN_VALUE: /* a simple boolean value */
case ECMA_INTERNAL_PROPERTY_CLASS: /* an enum */
case ECMA_INTERNAL_PROPERTY_CODE_BYTECODE: /* compressed pointer to a bytecode array */
case ECMA_INTERNAL_PROPERTY_CODE_FLAGS_AND_OFFSET: /* an integer */
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_ID: /* an integer */
case ECMA_INTERNAL_PROPERTY_EXTENSION_ID: /* 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) */
case ECMA_INTERNAL_PROPERTY_REGEXP_BYTECODE:
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_TARGET_FUNCTION:
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_BOUND_THIS:
case ECMA_INTERNAL_PROPERTY_BOUND_FUNCTION_BOUND_ARGS:
{
break;
}
case ECMA_INTERNAL_PROPERTY_SCOPE: /* a lexical environment */
case ECMA_INTERNAL_PROPERTY_PARAMETERS_MAP: /* an object */
{
ecma_object_t *obj_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, property_value);
ecma_gc_set_object_visited (obj_p, true);
break;
}
}
break;
}
}
}
}
} /* 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)
&& ecma_gc_get_object_refs (object_p) == 0);
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_OBJECTBOUND)
{
for (ecma_property_t *property = ecma_get_property_list (object_p), *next_property_p;
property != NULL;
property = next_property_p)
{
next_property_p = ECMA_GET_POINTER (ecma_property_t,
property->next_property_p);
ecma_free_property (object_p, property);
}
}
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 (ecma_gc_get_object_refs (obj_iter_p) > 0)
{
ecma_gc_set_object_visited (obj_iter_p, true);
}
}
/* if some object is referenced from a register variable (i.e. it is root),
* start recursive marking traverse from the object */
for (vm_stack_frame_t *frame_iter_p = vm_stack_get_top_frame ();
frame_iter_p != NULL;
frame_iter_p = frame_iter_p->prev_frame_p)
{
for (int32_t reg_index = 0; reg_index < frame_iter_p->regs_number; reg_index++)
{
ecma_value_t reg_value = vm_stack_frame_get_reg_value (frame_iter_p, reg_index);
if (ecma_is_value_object (reg_value))
{
ecma_object_t *obj_p = ecma_get_object_from_value (reg_value);
ecma_gc_set_object_visited (obj_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;
} /* ecma_gc_run */
/**
* Try to free some memory (depending on severity).
*/
void
ecma_try_to_give_back_some_memory (mem_try_give_memory_back_severity_t severity) /**< severity of
* the request */
{
if (severity == MEM_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 if (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_MEDIUM
|| severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH)
{
ecma_gc_run ();
}
else
{
JERRY_ASSERT (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
/* Freeing as much memory as we currently can */
ecma_lcache_invalidate_all ();
ecma_gc_run ();
}
} /* ecma_try_to_give_back_some_memory */
/**
* @}
* @}
*/