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 "debug/HWPrefetch.hh"
41#include "mem/cache/prefetch/queued.hh"
42#include "mem/cache/base.hh"
43
44QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p)
45 : BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency),
46 queueSquash(p->queue_squash), queueFilter(p->queue_filter),
47 cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch)
48{
49
50}
51
52QueuedPrefetcher::~QueuedPrefetcher()
53{
54 // Delete the queued prefetch packets
55 for (DeferredPacket &p : pfq) {
56 delete p.pkt->req;
57 delete p.pkt;
58 }
59}
60
61Tick
62QueuedPrefetcher::notify(const PacketPtr &pkt)
63{
64 // Verify this access type is observed by prefetcher
65 if (observeAccess(pkt)) {
66 Addr blk_addr = pkt->getBlockAddr(blkSize);
67 bool is_secure = pkt->isSecure();
68
69 // Squash queued prefetches if demand miss to same line
70 if (queueSquash) {
71 auto itr = pfq.begin();
72 while (itr != pfq.end()) {
73 if (itr->pkt->getAddr() == blk_addr &&
74 itr->pkt->isSecure() == is_secure) {
75 delete itr->pkt->req;
76 delete itr->pkt;
77 itr = pfq.erase(itr);
78 } else {
79 ++itr;
80 }
81 }
82 }
83
84 // Calculate prefetches given this access
85 std::vector<AddrPriority> addresses;
86 calculatePrefetch(pkt, addresses);
87
88 // Queue up generated prefetches
89 for (AddrPriority& pf_info : addresses) {
90
91 // Block align prefetch address
92 pf_info.first &= ~(Addr)(blkSize - 1);
93
94 pfIdentified++;
95 DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
96 "inserting into prefetch queue.\n", pf_info.first);
97
98 // Create and insert the request
99 PacketPtr pf_pkt = insert(pf_info, is_secure);
100
101 if (pf_pkt != nullptr) {
102 if (tagPrefetch && pkt->req->hasPC()) {
103 // Tag prefetch packet with accessing pc
104 pf_pkt->req->setPC(pkt->req->getPC());
105 }
106 }
107 }
108 }
109
110 return pfq.empty() ? MaxTick : pfq.front().tick;
111}
112
113PacketPtr
114QueuedPrefetcher::getPacket()
115{
116 DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
117
118 if (pfq.empty()) {
119 DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
120 return NULL;
121 }
122
123 PacketPtr pkt = pfq.begin()->pkt;
124 pfq.pop_front();
125
126 pfIssued++;
127 assert(pkt != NULL);
128 DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
129 return pkt;
130}
131
132std::list<QueuedPrefetcher::DeferredPacket>::const_iterator
133QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
134{
135 for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
136 if ((*dp).pkt->getAddr() == address &&
137 (*dp).pkt->isSecure() == is_secure) return dp;
138 }
139
140 return pfq.end();
141}
142
143QueuedPrefetcher::iterator
144QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
145{
146 for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
147 if (dp->pkt->getAddr() == address &&
148 dp->pkt->isSecure() == is_secure) return dp;
149 }
150
151 return pfq.end();
152}
153
154void
155QueuedPrefetcher::regStats()
156{
157 BasePrefetcher::regStats();
158
159 pfIdentified
160 .name(name() + ".pfIdentified")
161 .desc("number of prefetch candidates identified");
162
163 pfBufferHit
164 .name(name() + ".pfBufferHit")
165 .desc("number of redundant prefetches already in prefetch queue");
166
167 pfInCache
168 .name(name() + ".pfInCache")
169 .desc("number of redundant prefetches already in cache/mshr dropped");
170
171 pfRemovedFull
172 .name(name() + ".pfRemovedFull")
173 .desc("number of prefetches dropped due to prefetch queue size");
174
175 pfSpanPage
176 .name(name() + ".pfSpanPage")
177 .desc("number of prefetches not generated due to page crossing");
178}
179
180PacketPtr
181QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
182{
183 if (queueFilter) {
184 iterator it = inPrefetch(pf_info.first, is_secure);
185 /* If the address is already in the queue, update priority and leave */
186 if (it != pfq.end()) {
187 pfBufferHit++;
188 if (it->priority < pf_info.second) {
189 /* Update priority value and position in the queue */
190 it->priority = pf_info.second;
191 iterator prev = it;
192 bool cont = true;
193 while (cont && prev != pfq.begin()) {
194 prev--;
195 /* If the packet has higher priority, swap */
196 if (*it > *prev) {
197 std::swap(*it, *prev);
198 it = prev;
199 }
200 }
201 DPRINTF(HWPrefetch, "Prefetch addr already in "
202 "prefetch queue, priority updated\n");
203 } else {
204 DPRINTF(HWPrefetch, "Prefetch addr already in "
205 "prefetch queue\n");
206 }
207 return nullptr;
208 }
209 }
210
211 if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
212 inMissQueue(pf_info.first, is_secure))) {
213 pfInCache++;
214 DPRINTF(HWPrefetch, "Dropping redundant in "
215 "cache/MSHR prefetch addr:%#x\n", pf_info.first);
216 return nullptr;
217 }
218
219 /* Create a prefetch memory request */
220 Request *pf_req =
221 new Request(pf_info.first, blkSize, 0, masterId);
222
223 if (is_secure) {
224 pf_req->setFlags(Request::SECURE);
225 }
226 pf_req->taskId(ContextSwitchTaskId::Prefetcher);
227 PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
228 pf_pkt->allocate();
229
230 /* Verify prefetch buffer space for request */
231 if (pfq.size() == queueSize) {
232 pfRemovedFull++;
233 /* Lowest priority packet */
234 iterator it = pfq.end();
235 panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
236 --it;
237 /* Look for oldest in that level of priority */
238 panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
239 iterator prev = it;
240 bool cont = true;
241 /* While not at the head of the queue */
242 while (cont && prev != pfq.begin()) {
243 prev--;
244 /* While at the same level of priority */
245 cont = (*prev).priority == (*it).priority;
246 if (cont)
247 /* update pointer */
248 it = prev;
249 }
250 DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
251 "oldest packet, addr: %#x", it->pkt->getAddr());
252 delete it->pkt->req;
253 delete it->pkt;
254 pfq.erase(it);
255 }
256
257 Tick pf_time = curTick() + clockPeriod() * latency;
258 DPRINTF(HWPrefetch, "Prefetch queued. "
259 "addr:%#x priority: %3d tick:%lld.\n",
260 pf_info.first, pf_info.second, pf_time);
261
262 /* Create the packet and find the spot to insert it */
263 DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
264 if (pfq.size() == 0) {
265 pfq.emplace_back(dpp);
266 } else {
267 iterator it = pfq.end();
268 while (it != pfq.begin() && dpp > *it)
269 --it;
270 /* If we reach the head, we have to see if the new element is new head
271 * or not */
272 if (it == pfq.begin() && dpp <= *it)
273 it++;
274 pfq.insert(it, dpp);
275 }
276
277 return pf_pkt;
278}