def test_tso_write_latency(self):
"""Tests the measurements of write-latency in a TSO cache.
Write latency is complicated in TSO: writes normally do not add to the cache
latency, unless they are involved in a write buffer drain. Additionally, any
write executing when a write buffer drain happens contributes the remainder
of its cycles to the latency."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2,
False)
# Single write: should be buffered.
cache.write(5)
self.assertEqual(cache.latency, 0)
# A second write: should trip retire at N, but no effect on latency.
cache.write(10)
self.assertEqual(cache.latency, 0)
self.assertEqual(len(cache.write_buffer), 1)
# Force a drain.
cache.write(15) # 2 writes in buffer
cache.write(20) # 3 writes in buffer
cache.write(25) # 4 writes in buffer; buffer should be full.
cache.write(30) # Should force a drain.
# Latency will be 4 writes in buffer, plus the one that was processing.
self.assertEqual(cache.latency, 222 * 5)
self.assertEqual(len(cache.write_buffer), 1)
def test_tso_write_latency(self):
"""Tests the measurements of write-latency in a TSO cache.
Write latency is complicated in TSO: writes normally do not add to the cache
latency, unless they are involved in a write buffer drain. Additionally, any
write executing when a write buffer drain happens contributes the remainder
of its cycles to the latency."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2, False)
# Single write: should be buffered.
cache.write(5)
self.assertEqual(cache.latency, 0)
# A second write: should trip retire at N, but no effect on latency.
cache.write(10)
self.assertEqual(cache.latency, 0)
self.assertEqual(len(cache.write_buffer), 1)
# Force a drain.
cache.write(15) # 2 writes in buffer
cache.write(20) # 3 writes in buffer
cache.write(25) # 4 writes in buffer; buffer should be full.
cache.write(30) # Should force a drain.
# Latency will be 4 writes in buffer, plus the one that was processing.
self.assertEqual(cache.latency, 222*5)
self.assertEqual(len(cache.write_buffer), 1)
def test_tso_post_program_drain(self):
"""Test the post-program drain of the write buffer."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2,
False)
# Test that nothing changes if theres nothing in the write buffer.
cache.latency = 500
cache.notify_finished()
self.assertEqual(cache.latency, 500)
self.assertEqual(cache.write_buffer, [])
self.assertEqual(cache.write_finishes_at, None)
# Test that the write buffer is properly cleared if there is something in it.
cache.latency = 500
cache.write_buffer = [10, 20]
cache.write_finishes_at = 505
cache.notify_finished()
self.assertEqual(cache.latency, 505 + (2 * 222))
self.assertEqual(cache.write_buffer, [])
self.assertEqual(cache.write_finishes_at, None)
def test_tso_post_program_drain(self):
"""Test the post-program drain of the write buffer."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2, False)
# Test that nothing changes if theres nothing in the write buffer.
cache.latency = 500
cache.notify_finished()
self.assertEqual(cache.latency, 500)
self.assertEqual(cache.write_buffer, [])
self.assertEqual(cache.write_finishes_at, None)
# Test that the write buffer is properly cleared if there is something in it.
cache.latency = 500
cache.write_buffer = [10, 20]
cache.write_finishes_at = 505
cache.notify_finished()
self.assertEqual(cache.latency, 505 + (2 * 222))
self.assertEqual(cache.write_buffer, [])
self.assertEqual(cache.write_finishes_at, None)
def test_tso_drain_buffer(self):
"""Tests that the drain buffer logic in the TSO cache is correct."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2,
False)
# Check that draining a cache always clears it completely.
cache.write_buffer = [1]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = [1, 2]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = [3, 4, 5, 6, 7]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = []
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
# Check that when the buffer is drained, any ongoing writes are counted as latency.
cache.write_buffer = []
cache.latency = 20
cache.write_finishes_at = 126
cache._drain_write_buffer()
self.assertEqual(cache.latency, 126)
self.assertEqual(cache.write_finishes_at, None)
cache.write_buffer = [10, 20]
cache.latency = 20
cache.write_finishes_at = 126
cache._drain_write_buffer()
self.assertEqual(cache.latency, 126 + (2 * 222))
self.assertEqual(cache.write_finishes_at, None)
# Check that when the buffer is drained, all writes are counted.
cache.write_buffer = [10, 20, 30, 40]
cache.latency = 0
cache.write_finishes_at = None
cache._drain_write_buffer()
self.assertEqual(cache.latency, 4 * 222)
self.assertEqual(cache.write_finishes_at, None)
# Check that when drained, writes execute in the correct order.
cache.write_buffer = [10,
138] # Same slot (1), different tag (0 and 1).
cache.latency = 0
cache.write_finishes_at = None
cache._drain_write_buffer()
self.assertEqual(cache.latency, 2 * 222)
self.assertEqual(cache.get_cache_line(1).tag, 1)
self.assertEqual(cache.get_cache_line(1).state, SlotState.MODIFIED)
def test_tso_check_write_buffer(self):
"""Tests that the check-buffer logic in the TSO cache is correct."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2,
False)
# First, check that the method does nothing if a write is still processing.
cache.write_finishes_at = 15 # Fake a write in progress.
cache.write_buffer = [10, 5, 20] # Fake some writes.
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 15)
self.assertEqual(cache.latency, 0)
self.assertEqual(cache.write_buffer, [10, 5, 20])
# Check that if a write is not in process but there are less than N (here,
# 2) writes in the buffer, it still does nothing.
cache.write_finishes_at = None
cache.write_buffer = [10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, None)
self.assertEqual(cache.latency, 0)
self.assertEqual(cache.write_buffer, [10])
# Check that if a write is finished and there are less than N (here, 2)
# writes in the buffer, the write is cleared but thats it.
cache.write_finishes_at = 10
cache.latency = 15
cache.write_buffer = [10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, None)
self.assertEqual(cache.latency, 15)
self.assertEqual(cache.write_buffer, [10])
# Check that if a write is finished and there are N writes in the buffer,
# another write is retired, from the correct end of the line.
cache.write_finishes_at = 10
cache.latency = 15
cache.write_buffer = [10, 5]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 237)
self.assertEqual(cache.latency, 15)
self.assertEqual(cache.write_buffer, [5])
# Check that if a write is not in progress and there are N writes in the
# buffer, another write is retired, from the correct end of the line.
cache.write_finishes_at = None
cache.latency = 25
cache.write_buffer = [5, 10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 247)
self.assertEqual(cache.latency, 25)
self.assertEqual(cache.write_buffer, [10])
def test_tso_read_latency(self):
"""Tests the measurements of read-latency in a TSO cache."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2,
False)
# First test that write buffers are snooped correctly.
cache.write(5)
cache.read(5)
self.assertEqual(cache.latency, 1)
cache.latency = 0
# Test value that is in the L1 cache.
cache.read(4) # Prime the cache.
cache.latency = 0
cache.read(4)
self.assertEqual(cache.latency, 3)
cache.latency = 0
# Test value returned by other processor.
cache.read(19)
self.assertEqual(cache.latency, 23)
cache.latency = 0
# Test value returned by main memory.
# Duck-punch the fake bus to claim that it read from memory.
# (Don't you love Python? Such abuse! :D)
old_read_miss = FakeBus.read_miss
def new_read_miss(self, cache_id, address):
return True
FakeBus.read_miss = new_read_miss
cache.read(26)
self.assertEqual(cache.latency, 223)
# Restore the FakeBus class.
FakeBus.read_miss = old_read_miss
def test_tso_drain_buffer(self):
"""Tests that the drain buffer logic in the TSO cache is correct."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2, False)
# Check that draining a cache always clears it completely.
cache.write_buffer = [1]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = [1, 2]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = [3, 4, 5, 6, 7]
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
cache.write_buffer = []
cache._drain_write_buffer()
self.assertEqual(cache.write_buffer, [])
# Check that when the buffer is drained, any ongoing writes are counted as latency.
cache.write_buffer = []
cache.latency = 20
cache.write_finishes_at = 126
cache._drain_write_buffer()
self.assertEqual(cache.latency, 126)
self.assertEqual(cache.write_finishes_at, None)
cache.write_buffer = [10, 20]
cache.latency = 20
cache.write_finishes_at = 126
cache._drain_write_buffer()
self.assertEqual(cache.latency, 126 + (2 * 222))
self.assertEqual(cache.write_finishes_at, None)
# Check that when the buffer is drained, all writes are counted.
cache.write_buffer = [10, 20, 30, 40]
cache.latency = 0
cache.write_finishes_at = None
cache._drain_write_buffer()
self.assertEqual(cache.latency, 4 * 222)
self.assertEqual(cache.write_finishes_at, None)
# Check that when drained, writes execute in the correct order.
cache.write_buffer = [10, 138] # Same slot (1), different tag (0 and 1).
cache.latency = 0
cache.write_finishes_at = None
cache._drain_write_buffer()
self.assertEqual(cache.latency, 2 * 222)
self.assertEqual(cache.get_cache_line(1).tag, 1)
self.assertEqual(cache.get_cache_line(1).state, SlotState.MODIFIED)
def test_tso_check_write_buffer(self):
"""Tests that the check-buffer logic in the TSO cache is correct."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2, False)
# First, check that the method does nothing if a write is still processing.
cache.write_finishes_at = 15 # Fake a write in progress.
cache.write_buffer = [10, 5, 20] # Fake some writes.
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 15)
self.assertEqual(cache.latency, 0)
self.assertEqual(cache.write_buffer, [10, 5, 20])
# Check that if a write is not in process but there are less than N (here,
# 2) writes in the buffer, it still does nothing.
cache.write_finishes_at = None
cache.write_buffer = [10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, None)
self.assertEqual(cache.latency, 0)
self.assertEqual(cache.write_buffer, [10])
# Check that if a write is finished and there are less than N (here, 2)
# writes in the buffer, the write is cleared but thats it.
cache.write_finishes_at = 10
cache.latency = 15
cache.write_buffer = [10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, None)
self.assertEqual(cache.latency, 15)
self.assertEqual(cache.write_buffer, [10])
# Check that if a write is finished and there are N writes in the buffer,
# another write is retired, from the correct end of the line.
cache.write_finishes_at = 10
cache.latency = 15
cache.write_buffer = [10, 5]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 237)
self.assertEqual(cache.latency, 15)
self.assertEqual(cache.write_buffer, [5])
# Check that if a write is not in progress and there are N writes in the
# buffer, another write is retired, from the correct end of the line.
cache.write_finishes_at = None
cache.latency = 25
cache.write_buffer = [5, 10]
cache._check_write_buffer()
self.assertEqual(cache.write_finishes_at, 247)
self.assertEqual(cache.latency, 25)
self.assertEqual(cache.write_buffer, [10])
def test_tso_read_latency(self):
"""Tests the measurements of read-latency in a TSO cache."""
# Cache with 16 lines, 8 words/line, 4-write buffer with retire-at-2.
cache = TSOCache(1, 16, 8, self.fake_bus, self.fake_tracker, 4, 2, False)
# First test that write buffers are snooped correctly.
cache.write(5)
cache.read(5)
self.assertEqual(cache.latency, 1)
cache.latency = 0
# Test value that is in the L1 cache.
cache.read(4) # Prime the cache.
cache.latency = 0
cache.read(4)
self.assertEqual(cache.latency, 3)
cache.latency = 0
# Test value returned by other processor.
cache.read(19)
self.assertEqual(cache.latency, 23)
cache.latency = 0
# Test value returned by main memory.
# Duck-punch the fake bus to claim that it read from memory.
# (Don't you love Python? Such abuse! :D)
old_read_miss = FakeBus.read_miss
def new_read_miss(self, cache_id, address):
return True
FakeBus.read_miss = new_read_miss
cache.read(26)
self.assertEqual(cache.latency, 223)
# Restore the FakeBus class.
FakeBus.read_miss = old_read_miss