class GC(object):
"""
Simple semi-space copying GC
fromspace:
heap we are currently allocating objects in
tospace:
heap to copy live data to when fromspace is full
forwarding_table:
vector of bits, indicating for each pointer-sized word whether
it contains a forwarding pointer. See the 'copy' method for
an additional explanation
"""
layout = [
('fromspace', 'BumpAllocator[]'),
('tospace', 'BumpAllocator[]'),
('forwarding_table', 'BitVector[]'),
]
@jit
def __init__(self, initial_size=1024**2):
self.fromspace = BumpAllocator(initial_size)
self.tospace = BumpAllocator(initial_size)
self.init_forwarding_table()
#self.finalizers = {}
@jit
def init_forwarding_table(self):
"""Initialize an empty forwarding table for the heap"""
self.forwarding_table = BitVector(self.fromspace.size())
@jit('gc -> Pointer[int8] -> int64')
def offset(self, obj):
"""Offset of object in heap, used for marking forwarded objects"""
return (obj - self.fromspace.bottom()) >> ptr_size
@jit('gc -> Pointer[int8] -> uint64')
def forwarded(self, obj):
"""Whether this object was copied to tospace"""
return self.offset(obj) in self.forwarding_table
@jit('allocator -> size -> Pointer[int8]')
def alloc(self, size, top_of_stack):
obj = self.fromspace.alloc(size)
if obj == NULL:
# fromspace is full, collect garbage
self.collect(size, top_of_stack)
obj = self.fromspace.alloc(size)
# assert obj != NULL # MemoryError should have been raised by
# # collect, unless `obj` really is too large
return obj
@jit('gc -> int64 -> Pointer[StackFrame[]] -> void')
def collect(self, size, top_of_stack):
"""
Collect garbage by copying all live data to tospace, starting with
`roots`. If there is no or little garbage and we're running out of heap
space, grow the heap. `size` indicates the size of the requested memory.
This method may raise MemoryError.
For every root, we determine the trace function and call it on the root.
The trace function traces the object itself (since only it knows its
size), and traces its children:
def __flypy_trace__(self, gc):
obj = gc.trace((int8 *) self, sizeof(self))
obj.field1 = obj.field1.trace(gc)
...
obj.fieldN = obj.fieldN.trace(gc)
return obj
"""
# Copy all live data
for item in roots.find_roots(top_of_stack):
obj = head(item)
trace = head(tail(item))
trace(obj)
# Swap spaces and adjust heap if necessary
self.fromspace, self.tospace = self.tospace, self.fromspace
if self.resize_heap(size):
self.init_forwarding_table()
else:
self.forwarding_table.clear()
@jit
def resize_heap(self, mininum_size):
"""
Adjust heap size based on occupation ratio.
Returns True if the heap got resized.
NOTE: This may raise MemoryError
"""
ratio = occupation(self.fromspace, self.fromspace.offset + mininum_size)
size = self.fromspace.size() + mininum_size
if ratio > OCCUPATION_THRESHOLD_HI:
self.fromspace.resize(int(size * GROW_FACTOR))
elif ratio < OCCUPATION_THRESHOLD_LO:
self.fromspace.resize(int(size / GROW_FACTOR))
else:
return False
return True
@jit('gc -> Pointer[int8] -> int64 -> Pointer[int8]')
def trace(self, obj, size, trace_children):
"""
Mark the reachable object. We first check if the object is already
copied, in which case we're done. Otherwise, we copy the object to the
tospace, and we trace the children. The copy operation will mark
the object as copied in the forwarding table.
We call __flypy_trace__ to mark GC-tracked children. This method
is automatically generated, and allows us to avoid type tagging values
to determine pointer locations. It also patches pointers to copied
objects.
"""
#assert self.fromspace.bottom() <= obj < self.fromspace.top
if self.forwarded(obj):
# Object already copied, use forwarding pointer
forward_ptr_ptr = cast(obj, Pointer[Pointer[int8]])
dst_obj = forward_ptr_ptr[0]
return dst_obj
copied_obj = self.copy(obj, size)
trace_children(copied_obj)
return copied_obj
@jit('gc -> Pointer[int8] -> int64 -> Pointer[int8]')
def copy(self, obj, size):
"""
Copy the object (excluding its children!) to the tospace.
This writes a forwarding pointer in the fromspace after having
copied the object, and remembers doing so by writing a bit in the
forwarding table corresponding to the offset of the object.
We could determine the forwarding address for any object that has
pointers using the type, for instance by overwriting the first pointer
in the object with the new pointer, and checking in which address space
that pointer points.
However, we support tagless representations, and we may not have any
reference, like a mutable value with only integers. We cannot
safely determine whether an overwritten location is a forwarding
address, or actually a value that happens to fall in the range
of the to-space.
"""
dst_obj = self.tospace.alloc(size, type)
memcpy(obj, dst_obj, size)
forward_ptr_ptr = cast(obj, Pointer[Pointer[int8]])
forward_ptr_ptr[0] = dst_obj
self.forwarding_table.mark(self.offset(obj))
return dst_obj
def init_forwarding_table(self):
"""Initialize an empty forwarding table for the heap"""
self.forwarding_table = BitVector(self.fromspace.size())
class GC(object):
"""
Simple semi-space copying GC
fromspace:
heap we are currently allocating objects in
tospace:
heap to copy live data to when fromspace is full
forwarding_table:
vector of bits, indicating for each pointer-sized word whether
it contains a forwarding pointer. See the 'copy' method for
an additional explanation
"""
layout = [
('fromspace', 'BumpAllocator[]'),
('tospace', 'BumpAllocator[]'),
('forwarding_table', 'BitVector[]'),
]
@jit
def __init__(self, initial_size=1024**2):
self.fromspace = BumpAllocator(initial_size)
self.tospace = BumpAllocator(initial_size)
self.init_forwarding_table()
#self.finalizers = {}
@jit
def init_forwarding_table(self):
"""Initialize an empty forwarding table for the heap"""
self.forwarding_table = BitVector(self.fromspace.size())
@jit('gc -> Pointer[int8] -> int64')
def offset(self, obj):
"""Offset of object in heap, used for marking forwarded objects"""
return (obj - self.fromspace.bottom()) >> ptr_size
@jit('gc -> Pointer[int8] -> uint64')
def forwarded(self, obj):
"""Whether this object was copied to tospace"""
return self.offset(obj) in self.forwarding_table
@jit('allocator -> size -> Pointer[int8]')
def alloc(self, size, top_of_stack):
obj = self.fromspace.alloc(size)
if obj == NULL:
# fromspace is full, collect garbage
self.collect(size, top_of_stack)
obj = self.fromspace.alloc(size)
# assert obj != NULL # MemoryError should have been raised by
# # collect, unless `obj` really is too large
return obj
@jit('gc -> int64 -> Pointer[StackFrame[]] -> void')
def collect(self, size, top_of_stack):
"""
Collect garbage by copying all live data to tospace, starting with
`roots`. If there is no or little garbage and we're running out of heap
space, grow the heap. `size` indicates the size of the requested memory.
This method may raise MemoryError.
For every root, we determine the trace function and call it on the root.
The trace function traces the object itself (since only it knows its
size), and traces its children:
def __flypy_trace__(self, gc):
obj = gc.trace((int8 *) self, sizeof(self))
obj.field1 = obj.field1.trace(gc)
...
obj.fieldN = obj.fieldN.trace(gc)
return obj
"""
# Copy all live data
for item in roots.find_roots(top_of_stack):
obj = head(item)
trace = head(tail(item))
trace(obj)
# Swap spaces and adjust heap if necessary
self.fromspace, self.tospace = self.tospace, self.fromspace
if self.resize_heap(size):
self.init_forwarding_table()
else:
self.forwarding_table.clear()
@jit
def resize_heap(self, mininum_size):
"""
Adjust heap size based on occupation ratio.
Returns True if the heap got resized.
NOTE: This may raise MemoryError
"""
ratio = occupation(self.fromspace,
self.fromspace.offset + mininum_size)
size = self.fromspace.size() + mininum_size
if ratio > OCCUPATION_THRESHOLD_HI:
self.fromspace.resize(int(size * GROW_FACTOR))
elif ratio < OCCUPATION_THRESHOLD_LO:
self.fromspace.resize(int(size / GROW_FACTOR))
else:
return False
return True
@jit('gc -> Pointer[int8] -> int64 -> Pointer[int8]')
def trace(self, obj, size, trace_children):
"""
Mark the reachable object. We first check if the object is already
copied, in which case we're done. Otherwise, we copy the object to the
tospace, and we trace the children. The copy operation will mark
the object as copied in the forwarding table.
We call __flypy_trace__ to mark GC-tracked children. This method
is automatically generated, and allows us to avoid type tagging values
to determine pointer locations. It also patches pointers to copied
objects.
"""
#assert self.fromspace.bottom() <= obj < self.fromspace.top
if self.forwarded(obj):
# Object already copied, use forwarding pointer
forward_ptr_ptr = cast(obj, Pointer[Pointer[int8]])
dst_obj = forward_ptr_ptr[0]
return dst_obj
copied_obj = self.copy(obj, size)
trace_children(copied_obj)
return copied_obj
@jit('gc -> Pointer[int8] -> int64 -> Pointer[int8]')
def copy(self, obj, size):
"""
Copy the object (excluding its children!) to the tospace.
This writes a forwarding pointer in the fromspace after having
copied the object, and remembers doing so by writing a bit in the
forwarding table corresponding to the offset of the object.
We could determine the forwarding address for any object that has
pointers using the type, for instance by overwriting the first pointer
in the object with the new pointer, and checking in which address space
that pointer points.
However, we support tagless representations, and we may not have any
reference, like a mutable value with only integers. We cannot
safely determine whether an overwritten location is a forwarding
address, or actually a value that happens to fall in the range
of the to-space.
"""
dst_obj = self.tospace.alloc(size, type)
memcpy(obj, dst_obj, size)
forward_ptr_ptr = cast(obj, Pointer[Pointer[int8]])
forward_ptr_ptr[0] = dst_obj
self.forwarding_table.mark(self.offset(obj))
return dst_obj
def f(n):
v = BitVector(100)
set(v)
return check(v)
def init_forwarding_table(self):
"""Initialize an empty forwarding table for the heap"""
self.forwarding_table = BitVector(self.fromspace.size())
