Prefetcher.hh revision 11025:4872dbdea907 
1/*
2 * Copyright (c) 1999-2012 Mark D. Hill and David A. Wood
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef __MEM_RUBY_STRUCTURES_PREFETCHER_HH__
30#define __MEM_RUBY_STRUCTURES_PREFETCHER_HH__
31
32// Implements Power 4 like prefetching
33
34#include <bitset>
35
36#include "base/statistics.hh"
37#include "mem/ruby/common/Address.hh"
38#include "mem/ruby/network/MessageBuffer.hh"
39#include "mem/ruby/slicc_interface/AbstractController.hh"
40#include "mem/ruby/slicc_interface/RubyRequest.hh"
41#include "mem/ruby/system/System.hh"
42#include "params/Prefetcher.hh"
43#include "sim/sim_object.hh"
44#include "sim/system.hh"
45
46#define MAX_PF_INFLIGHT 8
47
48class PrefetchEntry
49{
50    public:
51        /// constructor
52        PrefetchEntry()
53        {
54            // default: 1 cache-line stride
55            m_stride   = (1 << RubySystem::getBlockSizeBits());
56            m_use_time = Cycles(0);
57            m_is_valid = false;
58        }
59
60        //! The base address for the stream prefetch
61        Addr m_address;
62
63        //! stride distance to get next address from
64        int m_stride;
65
66        //! the last time that any prefetched request was used
67        Cycles m_use_time;
68
69        //! valid bit for each stream
70        bool m_is_valid;
71
72        //! L1D prefetches loads and stores
73        RubyRequestType m_type;
74
75        //! Bitset for tracking prefetches for which addresses have been
76        //! issued, which ones have completed.
77        std::bitset<MAX_PF_INFLIGHT> requestIssued;
78        std::bitset<MAX_PF_INFLIGHT> requestCompleted;
79};
80
81class Prefetcher : public SimObject
82{
83    public:
84        typedef PrefetcherParams Params;
85        Prefetcher(const Params *p);
86        ~Prefetcher();
87
88        void issueNextPrefetch(Addr address, PrefetchEntry *stream);
89        /**
90         * Implement the prefetch hit(miss) callback interface.
91         * These functions are called by the cache when it hits(misses)
92         * on a line with the line's prefetch bit set. If this address
93         * hits in m_array we will continue prefetching the stream.
94         */
95        void observePfHit(Addr address);
96        void observePfMiss(Addr address);
97
98        /**
99         * Observe a memory miss from the cache.
100         *
101         * @param address   The physical address that missed out of the cache.
102         */
103        void observeMiss(Addr address, const RubyRequestType& type);
104
105        /**
106         * Print out some statistics
107         */
108        void print(std::ostream& out) const;
109        void setController(AbstractController *_ctrl)
110        { m_controller = _ctrl; }
111
112        void regStats();
113
114    private:
115        /**
116         * Returns an unused stream buffer (or if all are used, returns the
117         * least recently used (accessed) stream buffer).
118         * @return  The index of the least recently used stream buffer.
119         */
120        uint32_t getLRUindex(void);
121
122        //! clear a non-unit stride prefetcher entry
123        void clearNonunitEntry(uint32_t index);
124
125        //! allocate a new stream buffer at a specific index
126        void initializeStream(Addr address, int stride,
127            uint32_t index, const RubyRequestType& type);
128
129        //! get pointer to the matching stream entry, returns NULL if not found
130        //! index holds the multiple of the stride this address is.
131        PrefetchEntry* getPrefetchEntry(Addr address,
132            uint32_t &index);
133
134        /// access a unit stride filter to determine if there is a hit
135        bool accessUnitFilter(std::vector<Addr>& filter_table,
136            uint32_t *hit_table, uint32_t &index, Addr address,
137            int stride, bool &alloc);
138
139        /// access a unit stride filter to determine if there is a hit
140        bool accessNonunitFilter(Addr address, int *stride,
141            bool &alloc);
142
143        /// determine the page aligned address
144        Addr pageAddress(Addr addr) const;
145
146        //! number of prefetch streams available
147        uint32_t m_num_streams;
148        //! an array of the active prefetch streams
149        std::vector<PrefetchEntry> m_array;
150
151        //! number of misses I must see before allocating a stream
152        uint32_t m_train_misses;
153        //! number of initial prefetches to startup a stream
154        uint32_t m_num_startup_pfs;
155        //! number of stride filters
156        uint32_t m_num_unit_filters;
157        //! number of non-stride filters
158        uint32_t m_num_nonunit_filters;
159
160        /// a unit stride filter array: helps reduce BW requirement of
161        /// prefetching
162        std::vector<Addr> m_unit_filter;
163        /// a round robin pointer into the unit filter group
164        uint32_t m_unit_filter_index;
165        //! An array used to count the of times particular filter entries
166        //! have been hit
167        uint32_t *m_unit_filter_hit;
168
169        //! a negative nit stride filter array: helps reduce BW requirement
170        //! of prefetching
171        std::vector<Addr> m_negative_filter;
172        /// a round robin pointer into the negative filter group
173        uint32_t m_negative_filter_index;
174        /// An array used to count the of times particular filter entries
175        /// have been hit
176        uint32_t *m_negative_filter_hit;
177
178        /// a non-unit stride filter array: helps reduce BW requirement of
179        /// prefetching
180        std::vector<Addr> m_nonunit_filter;
181        /// An array of strides (in # of cache lines) for the filter entries
182        int *m_nonunit_stride;
183        /// An array used to count the of times particular filter entries
184        /// have been hit
185        uint32_t *m_nonunit_hit;
186        /// a round robin pointer into the unit filter group
187        uint32_t m_nonunit_index;
188
189        /// Used for allowing prefetches across pages.
190        bool m_prefetch_cross_pages;
191
192        AbstractController *m_controller;
193
194        const Addr m_page_shift;
195
196        //! Count of accesses to the prefetcher
197        Stats::Scalar numMissObserved;
198        //! Count of prefetch streams allocated
199        Stats::Scalar numAllocatedStreams;
200        //! Count of prefetch requests made
201        Stats::Scalar numPrefetchRequested;
202        //! Count of prefetch requests accepted
203        Stats::Scalar numPrefetchAccepted;
204        //! Count of prefetches dropped
205        Stats::Scalar numDroppedPrefetches;
206        //! Count of successful prefetches
207        Stats::Scalar numHits;
208        //! Count of partial successful prefetches
209        Stats::Scalar numPartialHits;
210        //! Count of pages crossed
211        Stats::Scalar numPagesCrossed;
212        //! Count of misses incurred for blocks that were prefetched
213        Stats::Scalar numMissedPrefetchedBlocks;
214};
215
216#endif // __MEM_RUBY_STRUCTURES_PREFETCHER_HH__
217