class OptimalMem(base.Memory):
def next(self, page, future_pages, **kwargs):
index = self.index(page)
if index is not None:
return False, index
for i, frame in enumerate(self.contents):
if frame.contents is None:
self.page_table[page.num] = i
frame.contents = page
return True, i
possible_frames = set(range(len(self.contents)))
for future_page in future_pages:
if len(possible_frames) > 1:
if future_page.num in self.page_table:
remove = self.page_table[future_page.num]
if remove in possible_frames:
possible_frames.remove(remove)
else:
break
assert(len(possible_frames) >= 1)
frame_index = possible_frames.pop()
frame = self.contents[frame_index]
del self.page_table[frame.contents.num]
self.page_table[page.num] = frame_index
frame.contents = page
return True, frame_index
base.run_cls(OptimalMem)
class LfuMem(base.Memory):
def __init__(self, n_frames):
base.Memory.__init__(self, n_frames)
self.frequency = [0] * n_frames
def next(self, page, **kwargs):
frame_index = self.index(page)
if frame_index is not None:
self.frequency[frame_index] += 1
return False, frame_index
frame_index = self.frequency.index(min(self.frequency))
frame = self.contents[frame_index]
if frame.contents is not None:
del self.page_table[frame.contents.num]
self.page_table[page.num] = frame_index
frame.contents = page
self.frequency[frame_index] = 1
return True, frame_index
def __repr__(self):
return (base.Memory.__repr__(self) + "\n" + "LFU access count " +
pprint.pformat(list(self.frequency)))
base.run_cls(LfuMem)
def next(self, page, **kwargs):
index = self.index(page)
if index is not None:
self.referenced[index] = 1
return False, index
self.last_insert_index += 1
self.last_insert_index %= len(self.contents)
while self.referenced[self.last_insert_index]:
self.referenced[self.last_insert_index] = 0
self.last_insert_index += 1
self.last_insert_index %= len(self.contents)
frame_index = self.last_insert_index
frame = self.contents[frame_index]
if frame.contents is not None:
del self.page_table[frame.contents.num]
frame.contents = page
self.page_table[page.num] = frame_index
self.referenced[frame_index] = 1
return True, frame_index
def __repr__(self):
return (base.Memory.__repr__(self) + "\n" + "Ref history " +
pprint.pformat(list(self.referenced)))
base.run_cls(LruScMem)
#!/usr/bin/env python3
import base
import pprint
class FifoMem(base.Memory):
def __init__(self, n_frames):
base.Memory.__init__(self, n_frames)
self.last_insert_index = -1 % n_frames
def next(self, page, **kwargs):
index = self.index(page)
if index is not None:
return False, index
self.last_insert_index += 1
self.last_insert_index %= len(self.contents)
frame_index = self.last_insert_index
frame = self.contents[frame_index]
if frame.contents is not None:
del self.page_table[frame.contents.num]
frame.contents = page
self.page_table[page.num] = frame_index
return True, frame_index
base.run_cls(FifoMem)
def next(self, page, **kwargs):
frame_index = self.index(page)
if frame_index is not None:
self.frequency[frame_index] += 1
return False, frame_index
for i, frame in enumerate(self.contents):
if frame.contents is None:
frame_index = i
break
else:
frame_index = self.frequency.index(max(self.frequency))
frame = self.contents[frame_index]
if frame.contents is not None:
del self.page_table[frame.contents.num]
self.page_table[page.num] = frame_index
frame.contents = page
self.frequency[frame_index] = 1
return True, frame_index
def __repr__(self):
return (base.Memory.__repr__(self) + "\n" + "MFU access count " +
pprint.pformat(list(self.frequency)))
base.run_cls(MfuMem)
class LruMem(base.Memory):
def __init__(self, n_frames):
base.Memory.__init__(self, n_frames)
self.history = deque(range(n_frames))
def next(self, page, **kwargs):
frame_index = self.index(page)
if frame_index is not None:
self.history.remove(frame_index)
self.history.append(frame_index)
return False, frame_index
frame_index = self.history.popleft()
self.history.append(frame_index)
frame = self.contents[frame_index]
if frame.contents is not None:
del self.page_table[frame.contents.num]
self.page_table[page.num] = frame_index
frame.contents = page
return True, frame_index
def __repr__(self):
return (base.Memory.__repr__(self) + "\n" +
"LRU history " + pprint.pformat(list(self.history)))
base.run_cls(LruMem)
victim = self.last_insert_index
victim_val = intify(victim)
if (not self.referenced[self.last_insert_index]
and not self.dirty[self.last_insert_index]):
victim = self.last_insert_index
break
self.referenced[self.last_insert_index] = 0
self.last_insert_index += 1
self.last_insert_index %= len(self.contents)
assert (victim is not None)
frame_index = victim
self.last_insert_index = victim
frame = self.contents[frame_index]
if frame.contents is not None:
self.dirty[frame_index] = 0
del self.page_table[frame.contents.num]
frame.contents = page
self.page_table[page.num] = frame_index
self.referenced[frame_index] = 1
return True, frame_index
def __repr__(self):
return (base.Memory.__repr__(self) + "\n" + "Ref history " +
pprint.pformat(list(self.referenced)) + "\n" +
"Dirty history " + pprint.pformat(list(self.dirty)))
base.run_cls(LruEscMem)