Prefetcher.py revision 13667:e3ae3619b9ab 
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13# Copyright (c) 2005 The Regents of The University of Michigan
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38#
39# Authors: Ron Dreslinski
40#          Mitch Hayenga
41
42from m5.SimObject import *
43from m5.params import *
44from m5.proxy import *
45
46from m5.objects.ClockedObject import ClockedObject
47from m5.objects.IndexingPolicies import *
48from m5.objects.ReplacementPolicies import *
49
50class HWPProbeEvent(object):
51    def __init__(self, prefetcher, obj, *listOfNames):
52        self.obj = obj
53        self.prefetcher = prefetcher
54        self.names = listOfNames
55
56    def register(self):
57        if self.obj:
58            for name in self.names:
59                self.prefetcher.getCCObject().addEventProbe(
60                    self.obj.getCCObject(), name)
61
62class BasePrefetcher(ClockedObject):
63    type = 'BasePrefetcher'
64    abstract = True
65    cxx_header = "mem/cache/prefetch/base.hh"
66    cxx_exports = [
67        PyBindMethod("addEventProbe"),
68    ]
69    sys = Param.System(Parent.any, "System this prefetcher belongs to")
70
71    # Get the block size from the parent (system)
72    block_size = Param.Int(Parent.cache_line_size, "Block size in bytes")
73
74    on_miss = Param.Bool(False, "Only notify prefetcher on misses")
75    on_read = Param.Bool(True, "Notify prefetcher on reads")
76    on_write = Param.Bool(True, "Notify prefetcher on writes")
77    on_data  = Param.Bool(True, "Notify prefetcher on data accesses")
78    on_inst  = Param.Bool(True, "Notify prefetcher on instruction accesses")
79    prefetch_on_access = Param.Bool(Parent.prefetch_on_access,
80        "Notify the hardware prefetcher on every access (not just misses)")
81    use_virtual_addresses = Param.Bool(False,
82        "Use virtual addresses for prefetching")
83
84    _events = []
85    def addEvent(self, newObject):
86        self._events.append(newObject)
87
88    # Override the normal SimObject::regProbeListeners method and
89    # register deferred event handlers.
90    def regProbeListeners(self):
91        for event in self._events:
92           event.register()
93        self.getCCObject().regProbeListeners()
94
95    def listenFromProbe(self, simObj, *probeNames):
96        if not isinstance(simObj, SimObject):
97            raise TypeError("argument must be of SimObject type")
98        if len(probeNames) <= 0:
99            raise TypeError("probeNames must have at least one element")
100        self.addEvent(HWPProbeEvent(self, simObj, *probeNames))
101
102class QueuedPrefetcher(BasePrefetcher):
103    type = "QueuedPrefetcher"
104    abstract = True
105    cxx_class = "QueuedPrefetcher"
106    cxx_header = "mem/cache/prefetch/queued.hh"
107    latency = Param.Int(1, "Latency for generated prefetches")
108    queue_size = Param.Int(32, "Maximum number of queued prefetches")
109    queue_squash = Param.Bool(True, "Squash queued prefetch on demand access")
110    queue_filter = Param.Bool(True, "Don't queue redundant prefetches")
111    cache_snoop = Param.Bool(False, "Snoop cache to eliminate redundant request")
112
113    tag_prefetch = Param.Bool(True, "Tag prefetch with PC of generating access")
114
115class StridePrefetcher(QueuedPrefetcher):
116    type = 'StridePrefetcher'
117    cxx_class = 'StridePrefetcher'
118    cxx_header = "mem/cache/prefetch/stride.hh"
119
120    # Do not consult stride prefetcher on instruction accesses
121    on_inst = False
122
123    max_conf = Param.Int(7, "Maximum confidence level")
124    thresh_conf = Param.Int(4, "Threshold confidence level")
125    min_conf = Param.Int(0, "Minimum confidence level")
126    start_conf = Param.Int(4, "Starting confidence for new entries")
127
128    table_sets = Param.Int(16, "Number of sets in PC lookup table")
129    table_assoc = Param.Int(4, "Associativity of PC lookup table")
130    use_master_id = Param.Bool(True, "Use master id based history")
131
132    degree = Param.Int(4, "Number of prefetches to generate")
133
134    # Get replacement policy
135    replacement_policy = Param.BaseReplacementPolicy(RandomRP(),
136        "Replacement policy")
137
138class TaggedPrefetcher(QueuedPrefetcher):
139    type = 'TaggedPrefetcher'
140    cxx_class = 'TaggedPrefetcher'
141    cxx_header = "mem/cache/prefetch/tagged.hh"
142
143    degree = Param.Int(2, "Number of prefetches to generate")
144
145class SignaturePathPrefetcher(QueuedPrefetcher):
146    type = 'SignaturePathPrefetcher'
147    cxx_class = 'SignaturePathPrefetcher'
148    cxx_header = "mem/cache/prefetch/signature_path.hh"
149
150    signature_shift = Param.UInt8(3,
151        "Number of bits to shift when calculating a new signature");
152    signature_bits = Param.UInt16(12,
153        "Size of the signature, in bits");
154    signature_table_entries = Param.MemorySize("1024",
155        "Number of entries of the signature table")
156    signature_table_assoc = Param.Unsigned(2,
157        "Associativity of the signature table")
158    signature_table_indexing_policy = Param.BaseIndexingPolicy(
159        SetAssociative(entry_size = 1, assoc = Parent.signature_table_assoc,
160        size = Parent.signature_table_entries),
161        "Indexing policy of the signature table")
162    signature_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
163        "Replacement policy of the signature table")
164
165    max_counter_value = Param.UInt8(7, "Maximum pattern counter value")
166    pattern_table_entries = Param.MemorySize("4096",
167        "Number of entries of the pattern table")
168    pattern_table_assoc = Param.Unsigned(1,
169        "Associativity of the pattern table")
170    strides_per_pattern_entry = Param.Unsigned(4,
171        "Number of strides stored in each pattern entry")
172    pattern_table_indexing_policy = Param.BaseIndexingPolicy(
173        SetAssociative(entry_size = 1, assoc = Parent.pattern_table_assoc,
174        size = Parent.pattern_table_entries),
175        "Indexing policy of the pattern table")
176    pattern_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
177        "Replacement policy of the pattern table")
178
179    prefetch_confidence_threshold = Param.Float(0.5,
180        "Minimum confidence to issue prefetches")
181    lookahead_confidence_threshold = Param.Float(0.75,
182        "Minimum confidence to continue exploring lookahead entries")
183
184class SignaturePathPrefetcherV2(SignaturePathPrefetcher):
185    type = 'SignaturePathPrefetcherV2'
186    cxx_class = 'SignaturePathPrefetcherV2'
187    cxx_header = "mem/cache/prefetch/signature_path_v2.hh"
188
189    signature_table_entries = "256"
190    signature_table_assoc = 1
191    pattern_table_entries = "512"
192    pattern_table_assoc = 1
193    max_counter_value = 15
194    prefetch_confidence_threshold = 0.25
195    lookahead_confidence_threshold = 0.25
196
197    global_history_register_entries = Param.MemorySize("8",
198        "Number of entries of global history register")
199    global_history_register_indexing_policy = Param.BaseIndexingPolicy(
200        SetAssociative(entry_size = 1,
201        assoc = Parent.global_history_register_entries,
202        size = Parent.global_history_register_entries),
203        "Indexing policy of the global history register")
204    global_history_register_replacement_policy = Param.BaseReplacementPolicy(
205        LRURP(), "Replacement policy of the global history register")
206
207class AccessMapPatternMatchingPrefetcher(QueuedPrefetcher):
208    type = 'AccessMapPatternMatchingPrefetcher'
209    cxx_class = 'AccessMapPatternMatchingPrefetcher'
210    cxx_header = "mem/cache/prefetch/access_map_pattern_matching.hh"
211
212    start_degree = Param.Unsigned(4,
213        "Initial degree (Maximum number of prefetches generated")
214    hot_zone_size = Param.MemorySize("2kB", "Memory covered by a hot zone")
215    access_map_table_entries = Param.MemorySize("256",
216        "Number of entries in the access map table")
217    access_map_table_assoc = Param.Unsigned(8,
218        "Associativity of the access map table")
219    access_map_table_indexing_policy = Param.BaseIndexingPolicy(
220        SetAssociative(entry_size = 1, assoc = Parent.access_map_table_assoc,
221        size = Parent.access_map_table_entries),
222        "Indexing policy of the access map table")
223    access_map_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
224        "Replacement policy of the access map table")
225    high_coverage_threshold = Param.Float(0.25,
226        "A prefetch coverage factor bigger than this is considered high")
227    low_coverage_threshold = Param.Float(0.125,
228        "A prefetch coverage factor smaller than this is considered low")
229    high_accuracy_threshold = Param.Float(0.5,
230        "A prefetch accuracy factor bigger than this is considered high")
231    low_accuracy_threshold = Param.Float(0.25,
232        "A prefetch accuracy factor smaller than this is considered low")
233    high_cache_hit_threshold = Param.Float(0.875,
234        "A cache hit ratio bigger than this is considered high")
235    low_cache_hit_threshold = Param.Float(0.75,
236        "A cache hit ratio smaller than this is considered low")
237    epoch_cycles = Param.Cycles(256000, "Cycles in an epoch period")
238    offchip_memory_latency = Param.Latency("30ns",
239        "Memory latency used to compute the required memory bandwidth")
240
241class DeltaCorrelatingPredictionTables(SimObject):
242    type = 'DeltaCorrelatingPredictionTables'
243    cxx_class = 'DeltaCorrelatingPredictionTables'
244    cxx_header = "mem/cache/prefetch/delta_correlating_prediction_tables.hh"
245    deltas_per_entry = Param.Unsigned(20,
246        "Number of deltas stored in each table entry")
247    delta_bits = Param.Unsigned(12, "Bits per delta")
248    delta_mask_bits = Param.Unsigned(8,
249        "Lower bits to mask when comparing deltas")
250    table_entries = Param.MemorySize("128",
251        "Number of entries in the table")
252    table_assoc = Param.Unsigned(128,
253        "Associativity of the table")
254    table_indexing_policy = Param.BaseIndexingPolicy(
255        SetAssociative(entry_size = 1, assoc = Parent.table_assoc,
256        size = Parent.table_entries),
257        "Indexing policy of the table")
258    table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
259        "Replacement policy of the table")
260
261class DCPTPrefetcher(QueuedPrefetcher):
262    type = 'DCPTPrefetcher'
263    cxx_class = 'DCPTPrefetcher'
264    cxx_header = "mem/cache/prefetch/delta_correlating_prediction_tables.hh"
265    dcpt = Param.DeltaCorrelatingPredictionTables(
266        DeltaCorrelatingPredictionTables(),
267        "Delta Correlating Prediction Tables object")
268
269