Prefetcher.hh revision 9363:e2616dc035ce 
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 PREFETCHER_H
30#define PREFETCHER_H
31
32// Implements Power 4 like prefetching
33
34#include <bitset>
35
36#include "base/statistics.hh"
37#include "mem/ruby/buffers/MessageBuffer.hh"
38#include "mem/ruby/common/Address.hh"
39#include "mem/ruby/common/Global.hh"
40#include "mem/ruby/slicc_interface/AbstractController.hh"
41#include "mem/ruby/slicc_interface/RubyRequest.hh"
42#include "params/Prefetcher.hh"
43#include "sim/sim_object.hh"
44
45#define MAX_PF_INFLIGHT 8
46
47class PrefetchEntry
48{
49    public:
50        /// constructor
51        PrefetchEntry()
52        {
53            // default: 1 cache-line stride
54            m_stride   = (1 << RubySystem::getBlockSizeBits());
55            m_use_time = Cycles(0);
56            m_is_valid = false;
57        }
58
59        //! The base address for the stream prefetch
60        Address m_address;
61
62        //! stride distance to get next address from
63        int m_stride;
64
65        //! the last time that any prefetched request was used
66        Cycles m_use_time;
67
68        //! valid bit for each stream
69        bool m_is_valid;
70
71        //! L1D prefetches loads and stores
72        RubyRequestType m_type;
73
74        //! Bitset for tracking prefetches for which addresses have been
75        //! issued, which ones have completed.
76        std::bitset<MAX_PF_INFLIGHT> requestIssued;
77        std::bitset<MAX_PF_INFLIGHT> requestCompleted;
78};
79
80class Prefetcher : public SimObject
81{
82    public:
83        typedef PrefetcherParams Params;
84        Prefetcher(const Params *p);
85        ~Prefetcher();
86
87        void issueNextPrefetch(const Address &address, PrefetchEntry *stream);
88        /**
89         * Implement the prefetch hit(miss) callback interface.
90         * These functions are called by the cache when it hits(misses)
91         * on a line with the line's prefetch bit set. If this address
92         * hits in m_array we will continue prefetching the stream.
93         */
94        void observePfHit(const Address& address);
95        void observePfMiss(const Address& address);
96
97        /**
98         * Observe a memory miss from the cache.
99         *
100         * @param address   The physical address that missed out of the cache.
101         */
102        void observeMiss(const Address& address, const RubyRequestType& type);
103
104        /**
105         * Print out some statistics
106         */
107        void print(std::ostream& out) const;
108        void setController(AbstractController *_ctrl)
109        { m_controller = _ctrl; }
110
111        void regStats();
112
113    private:
114        /**
115         * Returns an unused stream buffer (or if all are used, returns the
116         * least recently used (accessed) stream buffer).
117         * @return  The index of the least recently used stream buffer.
118         */
119        uint32_t getLRUindex(void);
120
121        //! clear a non-unit stride prefetcher entry
122        void clearNonunitEntry(uint32_t index);
123
124        //! allocate a new stream buffer at a specific index
125        void initializeStream(const Address& address, int stride,
126            uint32_t index, const RubyRequestType& type);
127
128        //! get pointer to the matching stream entry, returns NULL if not found
129        //! index holds the multiple of the stride this address is.
130        PrefetchEntry* getPrefetchEntry(const Address &address,
131            uint32_t &index);
132
133        /// access a unit stride filter to determine if there is a hit
134        bool accessUnitFilter(std::vector<Address>& filter_table,
135            uint32_t *hit_table, uint32_t &index, const Address &address,
136            int stride, bool &alloc);
137
138        /// access a unit stride filter to determine if there is a hit
139        bool accessNonunitFilter(const Address& address, int *stride,
140            bool &alloc);
141
142        //! number of prefetch streams available
143        uint32_t m_num_streams;
144        //! an array of the active prefetch streams
145        std::vector<PrefetchEntry> m_array;
146
147        //! number of misses I must see before allocating a stream
148        uint32_t m_train_misses;
149        //! number of initial prefetches to startup a stream
150        uint32_t m_num_startup_pfs;
151        //! number of stride filters
152        uint32_t m_num_unit_filters;
153        //! number of non-stride filters
154        uint32_t m_num_nonunit_filters;
155
156        /// a unit stride filter array: helps reduce BW requirement of
157        /// prefetching
158        std::vector<Address> m_unit_filter;
159        /// a round robin pointer into the unit filter group
160        uint32_t m_unit_filter_index;
161        //! An array used to count the of times particular filter entries
162        //! have been hit
163        uint32_t *m_unit_filter_hit;
164
165        //! a negative nit stride filter array: helps reduce BW requirement
166        //! of prefetching
167        std::vector<Address> m_negative_filter;
168        /// a round robin pointer into the negative filter group
169        uint32_t m_negative_filter_index;
170        /// An array used to count the of times particular filter entries
171        /// have been hit
172        uint32_t *m_negative_filter_hit;
173
174        /// a non-unit stride filter array: helps reduce BW requirement of
175        /// prefetching
176        std::vector<Address> m_nonunit_filter;
177        /// An array of strides (in # of cache lines) for the filter entries
178        int *m_nonunit_stride;
179        /// An array used to count the of times particular filter entries
180        /// have been hit
181        uint32_t *m_nonunit_hit;
182        /// a round robin pointer into the unit filter group
183        uint32_t m_nonunit_index;
184
185        /// Used for allowing prefetches across pages.
186        bool m_prefetch_cross_pages;
187
188        AbstractController *m_controller;
189
190        //! Count of accesses to the prefetcher
191        Stats::Scalar numMissObserved;
192        //! Count of prefetch streams allocated
193        Stats::Scalar numAllocatedStreams;
194        //! Count of prefetch requests made
195        Stats::Scalar numPrefetchRequested;
196        //! Count of prefetch requests accepted
197        Stats::Scalar numPrefetchAccepted;
198        //! Count of prefetches dropped
199        Stats::Scalar numDroppedPrefetches;
200        //! Count of successful prefetches
201        Stats::Scalar numHits;
202        //! Count of partial successful prefetches
203        Stats::Scalar numPartialHits;
204        //! Count of pages crossed
205        Stats::Scalar numPagesCrossed;
206        //! Count of misses incurred for blocks that were prefetched
207        Stats::Scalar numMissedPrefetchedBlocks;
208};
209
210#endif // PREFETCHER_H
211