Prefetcher.py revision 13624:3d8220c2d41d 
1# Copyright (c) 2012, 2014 ARM Limited
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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 ClockedObject import ClockedObject
43from IndexingPolicies import *
44from m5.SimObject import *
45from m5.params import *
46from m5.proxy import *
47from ReplacementPolicies import *
48
49class HWPProbeEvent(object):
50    def __init__(self, prefetcher, obj, *listOfNames):
51        self.obj = obj
52        self.prefetcher = prefetcher
53        self.names = listOfNames
54
55    def register(self):
56        if self.obj:
57            for name in self.names:
58                self.prefetcher.getCCObject().addEventProbe(
59                    self.obj.getCCObject(), name)
60
61class BasePrefetcher(ClockedObject):
62    type = 'BasePrefetcher'
63    abstract = True
64    cxx_header = "mem/cache/prefetch/base.hh"
65    cxx_exports = [
66        PyBindMethod("addEventProbe"),
67    ]
68    sys = Param.System(Parent.any, "System this prefetcher belongs to")
69
70    # Get the block size from the parent (system)
71    block_size = Param.Int(Parent.cache_line_size, "Block size in bytes")
72
73    on_miss = Param.Bool(False, "Only notify prefetcher on misses")
74    on_read = Param.Bool(True, "Notify prefetcher on reads")
75    on_write = Param.Bool(True, "Notify prefetcher on writes")
76    on_data  = Param.Bool(True, "Notify prefetcher on data accesses")
77    on_inst  = Param.Bool(True, "Notify prefetcher on instruction accesses")
78    prefetch_on_access = Param.Bool(Parent.prefetch_on_access,
79        "Notify the hardware prefetcher on every access (not just misses)")
80    use_virtual_addresses = Param.Bool(False,
81        "Use virtual addresses for prefetching")
82
83    _events = []
84    def addEvent(self, newObject):
85        self._events.append(newObject)
86
87    # Override the normal SimObject::regProbeListeners method and
88    # register deferred event handlers.
89    def regProbeListeners(self):
90        for event in self._events:
91           event.register()
92        self.getCCObject().regProbeListeners()
93
94    def listenFromProbe(self, simObj, *probeNames):
95        if not isinstance(simObj, SimObject):
96            raise TypeError("argument must be of SimObject type")
97        if len(probeNames) <= 0:
98            raise TypeError("probeNames must have at least one element")
99        self.addEvent(HWPProbeEvent(self, simObj, *probeNames))
100
101class QueuedPrefetcher(BasePrefetcher):
102    type = "QueuedPrefetcher"
103    abstract = True
104    cxx_class = "QueuedPrefetcher"
105    cxx_header = "mem/cache/prefetch/queued.hh"
106    latency = Param.Int(1, "Latency for generated prefetches")
107    queue_size = Param.Int(32, "Maximum number of queued prefetches")
108    queue_squash = Param.Bool(True, "Squash queued prefetch on demand access")
109    queue_filter = Param.Bool(True, "Don't queue redundant prefetches")
110    cache_snoop = Param.Bool(False, "Snoop cache to eliminate redundant request")
111
112    tag_prefetch = Param.Bool(True, "Tag prefetch with PC of generating access")
113
114class StridePrefetcher(QueuedPrefetcher):
115    type = 'StridePrefetcher'
116    cxx_class = 'StridePrefetcher'
117    cxx_header = "mem/cache/prefetch/stride.hh"
118
119    # Do not consult stride prefetcher on instruction accesses
120    on_inst = False
121
122    max_conf = Param.Int(7, "Maximum confidence level")
123    thresh_conf = Param.Int(4, "Threshold confidence level")
124    min_conf = Param.Int(0, "Minimum confidence level")
125    start_conf = Param.Int(4, "Starting confidence for new entries")
126
127    table_sets = Param.Int(16, "Number of sets in PC lookup table")
128    table_assoc = Param.Int(4, "Associativity of PC lookup table")
129    use_master_id = Param.Bool(True, "Use master id based history")
130
131    degree = Param.Int(4, "Number of prefetches to generate")
132
133    # Get replacement policy
134    replacement_policy = Param.BaseReplacementPolicy(RandomRP(),
135        "Replacement policy")
136
137class TaggedPrefetcher(QueuedPrefetcher):
138    type = 'TaggedPrefetcher'
139    cxx_class = 'TaggedPrefetcher'
140    cxx_header = "mem/cache/prefetch/tagged.hh"
141
142    degree = Param.Int(2, "Number of prefetches to generate")
143
144class SignaturePathPrefetcher(QueuedPrefetcher):
145    type = 'SignaturePathPrefetcher'
146    cxx_class = 'SignaturePathPrefetcher'
147    cxx_header = "mem/cache/prefetch/signature_path.hh"
148
149    signature_shift = Param.UInt8(3,
150        "Number of bits to shift when calculating a new signature");
151    signature_bits = Param.UInt16(12,
152        "Size of the signature, in bits");
153    signature_table_entries = Param.MemorySize("1024",
154        "Number of entries of the signature table")
155    signature_table_assoc = Param.Unsigned(2,
156        "Associativity of the signature table")
157    signature_table_indexing_policy = Param.BaseIndexingPolicy(
158        SetAssociative(entry_size = 1, assoc = Parent.signature_table_assoc,
159        size = Parent.signature_table_entries),
160        "Indexing policy of the signature table")
161    signature_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
162        "Replacement policy of the signature table")
163
164    max_counter_value = Param.UInt8(7, "Maximum pattern counter value")
165    pattern_table_entries = Param.MemorySize("4096",
166        "Number of entries of the pattern table")
167    pattern_table_assoc = Param.Unsigned(1,
168        "Associativity of the pattern table")
169    strides_per_pattern_entry = Param.Unsigned(4,
170        "Number of strides stored in each pattern entry")
171    pattern_table_indexing_policy = Param.BaseIndexingPolicy(
172        SetAssociative(entry_size = 1, assoc = Parent.pattern_table_assoc,
173        size = Parent.pattern_table_entries),
174        "Indexing policy of the pattern table")
175    pattern_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
176        "Replacement policy of the pattern table")
177
178    prefetch_confidence_threshold = Param.Float(0.5,
179        "Minimum confidence to issue prefetches")
180    lookahead_confidence_threshold = Param.Float(0.75,
181        "Minimum confidence to continue exploring lookahead entries")
182
183class SignaturePathPrefetcherV2(SignaturePathPrefetcher):
184    type = 'SignaturePathPrefetcherV2'
185    cxx_class = 'SignaturePathPrefetcherV2'
186    cxx_header = "mem/cache/prefetch/signature_path_v2.hh"
187
188    signature_table_entries = "256"
189    signature_table_assoc = 1
190    pattern_table_entries = "512"
191    pattern_table_assoc = 1
192    max_counter_value = 15
193    prefetch_confidence_threshold = 0.25
194    lookahead_confidence_threshold = 0.25
195
196    global_history_register_entries = Param.MemorySize("8",
197        "Number of entries of global history register")
198    global_history_register_indexing_policy = Param.BaseIndexingPolicy(
199        SetAssociative(entry_size = 1,
200        assoc = Parent.global_history_register_entries,
201        size = Parent.global_history_register_entries),
202        "Indexing policy of the global history register")
203    global_history_register_replacement_policy = Param.BaseReplacementPolicy(
204        LRURP(), "Replacement policy of the global history register")
205
206class AccessMapPatternMatchingPrefetcher(QueuedPrefetcher):
207    type = 'AccessMapPatternMatchingPrefetcher'
208    cxx_class = 'AccessMapPatternMatchingPrefetcher'
209    cxx_header = "mem/cache/prefetch/access_map_pattern_matching.hh"
210
211    start_degree = Param.Unsigned(4,
212        "Initial degree (Maximum number of prefetches generated")
213    hot_zone_size = Param.MemorySize("2kB", "Memory covered by a hot zone")
214    access_map_table_entries = Param.MemorySize("256",
215        "Number of entries in the access map table")
216    access_map_table_assoc = Param.Unsigned(8,
217        "Associativity of the access map table")
218    access_map_table_indexing_policy = Param.BaseIndexingPolicy(
219        SetAssociative(entry_size = 1, assoc = Parent.access_map_table_assoc,
220        size = Parent.access_map_table_entries),
221        "Indexing policy of the access map table")
222    access_map_table_replacement_policy = Param.BaseReplacementPolicy(LRURP(),
223        "Replacement policy of the access map table")
224    high_coverage_threshold = Param.Float(0.25,
225        "A prefetch coverage factor bigger than this is considered high")
226    low_coverage_threshold = Param.Float(0.125,
227        "A prefetch coverage factor smaller than this is considered low")
228    high_accuracy_threshold = Param.Float(0.5,
229        "A prefetch accuracy factor bigger than this is considered high")
230    low_accuracy_threshold = Param.Float(0.25,
231        "A prefetch accuracy factor smaller than this is considered low")
232    high_cache_hit_threshold = Param.Float(0.875,
233        "A cache hit ratio bigger than this is considered high")
234    low_cache_hit_threshold = Param.Float(0.75,
235        "A cache hit ratio smaller than this is considered low")
236    epoch_cycles = Param.Cycles(256000, "Cycles in an epoch period")
237    offchip_memory_latency = Param.Latency("30ns",
238        "Memory latency used to compute the required memory bandwidth")
239