src/mem/cache/prefetch/Prefetcher.py

   1 # Copyright (c) 2012, 2014 ARM Limited
   2 # All rights reserved.
   3 #
   4 # The license below extends only to copyright in the software and shall
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   7 # to a hardware implementation of the functionality of the software
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  11 # modified or unmodified, in source code or in binary form.
  12 #
  13 # Copyright (c) 2005 The Regents of The University of Michigan
  14 # All rights reserved.
  15 #
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  17 # modification, are permitted provided that the following conditions are
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  25 # this software without specific prior written permission.
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  27 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  30 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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  33 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  37 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  38 #
  39 # Authors: Ron Dreslinski
  40 #          Mitch Hayenga
  41
  42 from ClockedObject import ClockedObject
  43 from IndexingPolicies import *
  44 from m5.SimObject import *
  45 from m5.params import *
  46 from m5.proxy import *
  47 from ReplacementPolicies import *
  48
  49 class 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
  61 class 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
 101 class 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
 114 class 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
 137 class 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
 144 class 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")