1/*
2 * Copyright (c) 2014-2015 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 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Mitch Hayenga
38 */
39
40#include "mem/cache/prefetch/queued.hh"
41
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49
50QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p)
51 : BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency),
52 queueSquash(p->queue_squash), queueFilter(p->queue_filter),
53 cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch)
54{
55
56}
57
58QueuedPrefetcher::~QueuedPrefetcher()
59{
60 // Delete the queued prefetch packets
61 for (DeferredPacket &p : pfq) {
62 delete p.pkt->req;
63 delete p.pkt;
64 }
65}
66
67Tick
68QueuedPrefetcher::notify(const PacketPtr &pkt)
69{
70 // Verify this access type is observed by prefetcher
71 if (observeAccess(pkt)) {
72 Addr blk_addr = pkt->getBlockAddr(blkSize);
73 bool is_secure = pkt->isSecure();
74
75 // Squash queued prefetches if demand miss to same line
76 if (queueSquash) {
77 auto itr = pfq.begin();
78 while (itr != pfq.end()) {
79 if (itr->pkt->getAddr() == blk_addr &&
80 itr->pkt->isSecure() == is_secure) {
81 delete itr->pkt->req;
82 delete itr->pkt;
83 itr = pfq.erase(itr);
84 } else {
85 ++itr;
86 }
87 }
88 }
89
90 // Calculate prefetches given this access
91 std::vector<AddrPriority> addresses;
92 calculatePrefetch(pkt, addresses);
93
94 // Queue up generated prefetches
95 for (AddrPriority& pf_info : addresses) {
96
97 // Block align prefetch address
98 pf_info.first &= ~(Addr)(blkSize - 1);
99
100 pfIdentified++;
101 DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
102 "inserting into prefetch queue.\n", pf_info.first);
103
104 // Create and insert the request
105 PacketPtr pf_pkt = insert(pf_info, is_secure);
106
107 if (pf_pkt != nullptr) {
108 if (tagPrefetch && pkt->req->hasPC()) {
109 // Tag prefetch packet with accessing pc
110 pf_pkt->req->setPC(pkt->req->getPC());
111 }
112 }
113 }
114 }
115
116 return pfq.empty() ? MaxTick : pfq.front().tick;
117}
118
119PacketPtr
120QueuedPrefetcher::getPacket()
121{
122 DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
123
124 if (pfq.empty()) {
125 DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
126 return nullptr;
127 }
128
129 PacketPtr pkt = pfq.begin()->pkt;
130 pfq.pop_front();
131
132 pfIssued++;
133 assert(pkt != nullptr);
134 DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
135 return pkt;
136}
137
138std::list<QueuedPrefetcher::DeferredPacket>::const_iterator
139QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
140{
141 for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
142 if ((*dp).pkt->getAddr() == address &&
143 (*dp).pkt->isSecure() == is_secure) return dp;
144 }
145
146 return pfq.end();
147}
148
149QueuedPrefetcher::iterator
150QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
151{
152 for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
153 if (dp->pkt->getAddr() == address &&
154 dp->pkt->isSecure() == is_secure) return dp;
155 }
156
157 return pfq.end();
158}
159
160void
161QueuedPrefetcher::regStats()
162{
163 BasePrefetcher::regStats();
164
165 pfIdentified
166 .name(name() + ".pfIdentified")
167 .desc("number of prefetch candidates identified");
168
169 pfBufferHit
170 .name(name() + ".pfBufferHit")
171 .desc("number of redundant prefetches already in prefetch queue");
172
173 pfInCache
174 .name(name() + ".pfInCache")
175 .desc("number of redundant prefetches already in cache/mshr dropped");
176
177 pfRemovedFull
178 .name(name() + ".pfRemovedFull")
179 .desc("number of prefetches dropped due to prefetch queue size");
180
181 pfSpanPage
182 .name(name() + ".pfSpanPage")
183 .desc("number of prefetches not generated due to page crossing");
184}
185
186PacketPtr
187QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
188{
189 if (queueFilter) {
190 iterator it = inPrefetch(pf_info.first, is_secure);
191 /* If the address is already in the queue, update priority and leave */
192 if (it != pfq.end()) {
193 pfBufferHit++;
194 if (it->priority < pf_info.second) {
195 /* Update priority value and position in the queue */
196 it->priority = pf_info.second;
197 iterator prev = it;
198 bool cont = true;
199 while (cont && prev != pfq.begin()) {
200 prev--;
201 /* If the packet has higher priority, swap */
202 if (*it > *prev) {
203 std::swap(*it, *prev);
204 it = prev;
205 }
206 }
207 DPRINTF(HWPrefetch, "Prefetch addr already in "
208 "prefetch queue, priority updated\n");
209 } else {
210 DPRINTF(HWPrefetch, "Prefetch addr already in "
211 "prefetch queue\n");
212 }
213 return nullptr;
214 }
215 }
216
217 if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
218 inMissQueue(pf_info.first, is_secure))) {
219 pfInCache++;
220 DPRINTF(HWPrefetch, "Dropping redundant in "
221 "cache/MSHR prefetch addr:%#x\n", pf_info.first);
222 return nullptr;
223 }
224
225 /* Create a prefetch memory request */
226 Request *pf_req =
227 new Request(pf_info.first, blkSize, 0, masterId);
228
229 if (is_secure) {
230 pf_req->setFlags(Request::SECURE);
231 }
232 pf_req->taskId(ContextSwitchTaskId::Prefetcher);
233 PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
234 pf_pkt->allocate();
235
236 /* Verify prefetch buffer space for request */
237 if (pfq.size() == queueSize) {
238 pfRemovedFull++;
239 /* Lowest priority packet */
240 iterator it = pfq.end();
241 panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
242 --it;
243 /* Look for oldest in that level of priority */
244 panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
245 iterator prev = it;
246 bool cont = true;
247 /* While not at the head of the queue */
248 while (cont && prev != pfq.begin()) {
249 prev--;
250 /* While at the same level of priority */
251 cont = (*prev).priority == (*it).priority;
252 if (cont)
253 /* update pointer */
254 it = prev;
255 }
256 DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
257 "oldest packet, addr: %#x", it->pkt->getAddr());
258 delete it->pkt->req;
259 delete it->pkt;
260 pfq.erase(it);
261 }
262
263 Tick pf_time = curTick() + clockPeriod() * latency;
264 DPRINTF(HWPrefetch, "Prefetch queued. "
265 "addr:%#x priority: %3d tick:%lld.\n",
266 pf_info.first, pf_info.second, pf_time);
267
268 /* Create the packet and find the spot to insert it */
269 DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
270 if (pfq.size() == 0) {
271 pfq.emplace_back(dpp);
272 } else {
273 iterator it = pfq.end();
274 while (it != pfq.begin() && dpp > *it)
275 --it;
276 /* If we reach the head, we have to see if the new element is new head
277 * or not */
278 if (it == pfq.begin() && dpp <= *it)
279 it++;
280 pfq.insert(it, dpp);
281 }
282
283 return pf_pkt;
284}
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