stride.cc (10627:63edd4a1243f) stride.cc (10771:ea35886cd847)
1/*
1/*
2 * Copyright (c) 2012-2013 ARM Limited
2 * Copyright (c) 2012-2013, 2015 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ron Dreslinski
41 * Steve Reinhardt
42 */
43
44/**
45 * @file
46 * Stride Prefetcher template instantiations.
47 */
48
49#include "base/random.hh"
50#include "debug/HWPrefetch.hh"
51#include "mem/cache/prefetch/stride.hh"
52
53StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p)
54 : QueuedPrefetcher(p),
55 maxConf(p->max_conf),
56 threshConf(p->thresh_conf),
57 minConf(p->min_conf),
58 startConf(p->start_conf),
59 pcTableAssoc(p->table_assoc),
60 pcTableSets(p->table_sets),
61 useMasterId(p->use_master_id),
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ron Dreslinski
41 * Steve Reinhardt
42 */
43
44/**
45 * @file
46 * Stride Prefetcher template instantiations.
47 */
48
49#include "base/random.hh"
50#include "debug/HWPrefetch.hh"
51#include "mem/cache/prefetch/stride.hh"
52
53StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p)
54 : QueuedPrefetcher(p),
55 maxConf(p->max_conf),
56 threshConf(p->thresh_conf),
57 minConf(p->min_conf),
58 startConf(p->start_conf),
59 pcTableAssoc(p->table_assoc),
60 pcTableSets(p->table_sets),
61 useMasterId(p->use_master_id),
62 degree(p->degree)
62 degree(p->degree),
63 pcTable(pcTableAssoc, pcTableSets, name())
63{
64 // Don't consult stride prefetcher on instruction accesses
65 onInst = false;
66
67 assert(isPowerOf2(pcTableSets));
64{
65 // Don't consult stride prefetcher on instruction accesses
66 onInst = false;
67
68 assert(isPowerOf2(pcTableSets));
69}
68
70
69 for (int c = 0; c < maxContexts; c++) {
70 pcTable[c] = new StrideEntry*[pcTableSets];
71 for (int s = 0; s < pcTableSets; s++) {
72 pcTable[c][s] = new StrideEntry[pcTableAssoc];
73 }
71StridePrefetcher::StrideEntry**
72StridePrefetcher::PCTable::allocateNewContext(int context)
73{
74 auto res = entries.insert(std::make_pair(context,
75 new StrideEntry*[pcTableSets]));
76 auto it = res.first;
77 chatty_assert(res.second, "Allocating an already created context\n");
78 assert(it->first == context);
79
80 DPRINTF(HWPrefetch, "Adding context %i with stride entries at %p\n",
81 context, it->second);
82
83 StrideEntry** entry = it->second;
84 for (int s = 0; s < pcTableSets; s++) {
85 entry[s] = new StrideEntry[pcTableAssoc];
74 }
86 }
87 return entry;
75}
76
88}
89
77StridePrefetcher::~StridePrefetcher()
78{
79 for (int c = 0; c < maxContexts; c++) {
90StridePrefetcher::PCTable::~PCTable() {
91 for (auto entry : entries) {
80 for (int s = 0; s < pcTableSets; s++) {
92 for (int s = 0; s < pcTableSets; s++) {
81 delete[] pcTable[c][s];
93 delete[] entry.second[s];
82 }
94 }
95 delete[] entry.second;
83 }
84}
85
86void
87StridePrefetcher::calculatePrefetch(const PacketPtr &pkt,
88 std::vector<Addr> &addresses)
89{
90 if (!pkt->req->hasPC()) {
91 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n");
92 return;
93 }
94
95 // Get required packet info
96 Addr pkt_addr = pkt->getAddr();
97 Addr pc = pkt->req->getPC();
98 bool is_secure = pkt->isSecure();
99 MasterID master_id = useMasterId ? pkt->req->masterId() : 0;
100
96 }
97}
98
99void
100StridePrefetcher::calculatePrefetch(const PacketPtr &pkt,
101 std::vector<Addr> &addresses)
102{
103 if (!pkt->req->hasPC()) {
104 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n");
105 return;
106 }
107
108 // Get required packet info
109 Addr pkt_addr = pkt->getAddr();
110 Addr pc = pkt->req->getPC();
111 bool is_secure = pkt->isSecure();
112 MasterID master_id = useMasterId ? pkt->req->masterId() : 0;
113
101 assert(master_id < maxContexts);
102
103 // Lookup pc-based information
104 StrideEntry *entry;
105
106 if(pcTableHit(pc, is_secure, master_id, entry)) {
107 // Hit in table
108 int new_stride = pkt_addr - entry->lastAddr;
109 bool stride_match = (new_stride == entry->stride);
110
111 // Adjust confidence for stride entry
112 if (stride_match && new_stride != 0) {
113 if (entry->confidence < maxConf)
114 entry->confidence++;
115 } else {
116 if (entry->confidence > minConf)
117 entry->confidence--;
118 // If confidence has dropped below the threshold, train new stride
119 if (entry->confidence < threshConf)
120 entry->stride = new_stride;
121 }
122
123 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), "
124 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride,
125 stride_match ? "match" : "change",
126 entry->confidence);
127
128 entry->lastAddr = pkt_addr;
129
130 // Abort prefetch generation if below confidence threshold
131 if (entry->confidence < threshConf)
132 return;
133
134 // Generate up to degree prefetches
135 for (int d = 1; d <= degree; d++) {
136 // Round strides up to atleast 1 cacheline
137 int prefetch_stride = new_stride;
138 if (abs(new_stride) < blkSize) {
139 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize;
140 }
141
142 Addr new_addr = pkt_addr + d * prefetch_stride;
143 if (samePage(pkt_addr, new_addr)) {
144 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr);
145 addresses.push_back(new_addr);
146 } else {
147 // Record the number of page crossing prefetches generated
148 pfSpanPage += degree - d + 1;
149 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n");
150 return;
151 }
152 }
153 } else {
154 // Miss in table
155 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr,
156 is_secure ? "s" : "ns");
157
158 StrideEntry* entry = pcTableVictim(pc, master_id);
159 entry->instAddr = pc;
160 entry->lastAddr = pkt_addr;
161 entry->isSecure= is_secure;
162 entry->stride = 0;
163 entry->confidence = startConf;
164 }
165}
166
167inline Addr
168StridePrefetcher::pcHash(Addr pc) const
169{
170 Addr hash1 = pc >> 1;
171 Addr hash2 = hash1 >> floorLog2(pcTableSets);
172 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1);
173}
174
175inline StridePrefetcher::StrideEntry*
176StridePrefetcher::pcTableVictim(Addr pc, int master_id)
177{
178 // Rand replacement for now
179 int set = pcHash(pc);
180 int way = random_mt.random<int>(0, pcTableAssoc - 1);
181
182 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way);
183 return &pcTable[master_id][set][way];
184}
185
186inline bool
187StridePrefetcher::pcTableHit(Addr pc, bool is_secure, int master_id,
188 StrideEntry* &entry)
189{
190 int set = pcHash(pc);
191 StrideEntry* set_entries = pcTable[master_id][set];
192 for (int way = 0; way < pcTableAssoc; way++) {
193 // Search ways for match
194 if (set_entries[way].instAddr == pc &&
195 set_entries[way].isSecure == is_secure) {
196 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way);
197 entry = &set_entries[way];
198 return true;
199 }
200 }
201 return false;
202}
203
204StridePrefetcher*
205StridePrefetcherParams::create()
206{
207 return new StridePrefetcher(this);
208}
114 // Lookup pc-based information
115 StrideEntry *entry;
116
117 if(pcTableHit(pc, is_secure, master_id, entry)) {
118 // Hit in table
119 int new_stride = pkt_addr - entry->lastAddr;
120 bool stride_match = (new_stride == entry->stride);
121
122 // Adjust confidence for stride entry
123 if (stride_match && new_stride != 0) {
124 if (entry->confidence < maxConf)
125 entry->confidence++;
126 } else {
127 if (entry->confidence > minConf)
128 entry->confidence--;
129 // If confidence has dropped below the threshold, train new stride
130 if (entry->confidence < threshConf)
131 entry->stride = new_stride;
132 }
133
134 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), "
135 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride,
136 stride_match ? "match" : "change",
137 entry->confidence);
138
139 entry->lastAddr = pkt_addr;
140
141 // Abort prefetch generation if below confidence threshold
142 if (entry->confidence < threshConf)
143 return;
144
145 // Generate up to degree prefetches
146 for (int d = 1; d <= degree; d++) {
147 // Round strides up to atleast 1 cacheline
148 int prefetch_stride = new_stride;
149 if (abs(new_stride) < blkSize) {
150 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize;
151 }
152
153 Addr new_addr = pkt_addr + d * prefetch_stride;
154 if (samePage(pkt_addr, new_addr)) {
155 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr);
156 addresses.push_back(new_addr);
157 } else {
158 // Record the number of page crossing prefetches generated
159 pfSpanPage += degree - d + 1;
160 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n");
161 return;
162 }
163 }
164 } else {
165 // Miss in table
166 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr,
167 is_secure ? "s" : "ns");
168
169 StrideEntry* entry = pcTableVictim(pc, master_id);
170 entry->instAddr = pc;
171 entry->lastAddr = pkt_addr;
172 entry->isSecure= is_secure;
173 entry->stride = 0;
174 entry->confidence = startConf;
175 }
176}
177
178inline Addr
179StridePrefetcher::pcHash(Addr pc) const
180{
181 Addr hash1 = pc >> 1;
182 Addr hash2 = hash1 >> floorLog2(pcTableSets);
183 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1);
184}
185
186inline StridePrefetcher::StrideEntry*
187StridePrefetcher::pcTableVictim(Addr pc, int master_id)
188{
189 // Rand replacement for now
190 int set = pcHash(pc);
191 int way = random_mt.random<int>(0, pcTableAssoc - 1);
192
193 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way);
194 return &pcTable[master_id][set][way];
195}
196
197inline bool
198StridePrefetcher::pcTableHit(Addr pc, bool is_secure, int master_id,
199 StrideEntry* &entry)
200{
201 int set = pcHash(pc);
202 StrideEntry* set_entries = pcTable[master_id][set];
203 for (int way = 0; way < pcTableAssoc; way++) {
204 // Search ways for match
205 if (set_entries[way].instAddr == pc &&
206 set_entries[way].isSecure == is_secure) {
207 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way);
208 entry = &set_entries[way];
209 return true;
210 }
211 }
212 return false;
213}
214
215StridePrefetcher*
216StridePrefetcherParams::create()
217{
218 return new StridePrefetcher(this);
219}