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
42#include <cassert>
43
44#include "base/logging.hh"
45#include "base/trace.hh"
46#include "debug/HWPrefetch.hh"
47#include "mem/request.hh"
48#include "params/QueuedPrefetcher.hh"
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;
63 }
64}
65
66void
67QueuedPrefetcher::notify(const PacketPtr &pkt)
68{
69 // Verify this access type is observed by prefetcher
70 if (observeAccess(pkt)) {
71 Addr blk_addr = pkt->getBlockAddr(blkSize);
72 bool is_secure = pkt->isSecure();
73
74 // Squash queued prefetches if demand miss to same line
75 if (queueSquash) {
76 auto itr = pfq.begin();
77 while (itr != pfq.end()) {
78 if (itr->pkt->getAddr() == blk_addr &&
79 itr->pkt->isSecure() == is_secure) {
80 delete itr->pkt;
81 itr = pfq.erase(itr);
82 } else {
83 ++itr;
84 }
85 }
86 }
87
88 // Calculate prefetches given this access
89 std::vector<AddrPriority> addresses;
90 calculatePrefetch(pkt, addresses);
91
92 // Queue up generated prefetches
93 for (AddrPriority& pf_info : addresses) {
94
95 // Block align prefetch address
96 pf_info.first &= ~(Addr)(blkSize - 1);
97
98 pfIdentified++;
99 DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
100 "inserting into prefetch queue.\n", pf_info.first);
101
102 // Create and insert the request
103 PacketPtr pf_pkt = insert(pf_info, is_secure);
104
105 if (pf_pkt != nullptr) {
106 if (tagPrefetch && pkt->req->hasPC()) {
107 // Tag prefetch packet with accessing pc
108 pf_pkt->req->setPC(pkt->req->getPC());
109 }
110 }
111 }
112 }
113}
114
115PacketPtr
116QueuedPrefetcher::getPacket()
117{
118 DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
119
120 if (pfq.empty()) {
121 DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
122 return nullptr;
123 }
124
125 PacketPtr pkt = pfq.begin()->pkt;
126 pfq.pop_front();
127
128 pfIssued++;
129 assert(pkt != nullptr);
130 DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
131 return pkt;
132}
133
134std::list<QueuedPrefetcher::DeferredPacket>::const_iterator
135QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
136{
137 for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
138 if ((*dp).pkt->getAddr() == address &&
139 (*dp).pkt->isSecure() == is_secure) return dp;
140 }
141
142 return pfq.end();
143}
144
145QueuedPrefetcher::iterator
146QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
147{
148 for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
149 if (dp->pkt->getAddr() == address &&
150 dp->pkt->isSecure() == is_secure) return dp;
151 }
152
153 return pfq.end();
154}
155
156void
157QueuedPrefetcher::regStats()
158{
159 BasePrefetcher::regStats();
160
161 pfIdentified
162 .name(name() + ".pfIdentified")
163 .desc("number of prefetch candidates identified");
164
165 pfBufferHit
166 .name(name() + ".pfBufferHit")
167 .desc("number of redundant prefetches already in prefetch queue");
168
169 pfInCache
170 .name(name() + ".pfInCache")
171 .desc("number of redundant prefetches already in cache/mshr dropped");
172
173 pfRemovedFull
174 .name(name() + ".pfRemovedFull")
175 .desc("number of prefetches dropped due to prefetch queue size");
176
177 pfSpanPage
178 .name(name() + ".pfSpanPage")
179 .desc("number of prefetches not generated due to page crossing");
180}
181
182PacketPtr
183QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
184{
185 if (queueFilter) {
186 iterator it = inPrefetch(pf_info.first, is_secure);
187 /* If the address is already in the queue, update priority and leave */
188 if (it != pfq.end()) {
189 pfBufferHit++;
190 if (it->priority < pf_info.second) {
191 /* Update priority value and position in the queue */
192 it->priority = pf_info.second;
193 iterator prev = it;
194 bool cont = true;
195 while (cont && prev != pfq.begin()) {
196 prev--;
197 /* If the packet has higher priority, swap */
198 if (*it > *prev) {
199 std::swap(*it, *prev);
200 it = prev;
201 }
202 }
203 DPRINTF(HWPrefetch, "Prefetch addr already in "
204 "prefetch queue, priority updated\n");
205 } else {
206 DPRINTF(HWPrefetch, "Prefetch addr already in "
207 "prefetch queue\n");
208 }
209 return nullptr;
210 }
211 }
212
213 if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
214 inMissQueue(pf_info.first, is_secure))) {
215 pfInCache++;
216 DPRINTF(HWPrefetch, "Dropping redundant in "
217 "cache/MSHR prefetch addr:%#x\n", pf_info.first);
218 return nullptr;
219 }
220
221 /* Create a prefetch memory request */
222 RequestPtr pf_req =
223 std::make_shared<Request>(pf_info.first, blkSize, 0, masterId);
224
225 if (is_secure) {
226 pf_req->setFlags(Request::SECURE);
227 }
228 pf_req->taskId(ContextSwitchTaskId::Prefetcher);
229 PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
230 pf_pkt->allocate();
231
232 /* Verify prefetch buffer space for request */
233 if (pfq.size() == queueSize) {
234 pfRemovedFull++;
235 /* Lowest priority packet */
236 iterator it = pfq.end();
237 panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
238 --it;
239 /* Look for oldest in that level of priority */
240 panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
241 iterator prev = it;
242 bool cont = true;
243 /* While not at the head of the queue */
244 while (cont && prev != pfq.begin()) {
245 prev--;
246 /* While at the same level of priority */
247 cont = (*prev).priority == (*it).priority;
248 if (cont)
249 /* update pointer */
250 it = prev;
251 }
252 DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
253 "oldest packet, addr: %#x", it->pkt->getAddr());
254 delete it->pkt;
255 pfq.erase(it);
256 }
257
258 Tick pf_time = curTick() + clockPeriod() * latency;
259 DPRINTF(HWPrefetch, "Prefetch queued. "
260 "addr:%#x priority: %3d tick:%lld.\n",
261 pf_info.first, pf_info.second, pf_time);
262
263 /* Create the packet and find the spot to insert it */
264 DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
265 if (pfq.size() == 0) {
266 pfq.emplace_back(dpp);
267 } else {
268 iterator it = pfq.end();
269 while (it != pfq.begin() && dpp > *it)
270 --it;
271 /* If we reach the head, we have to see if the new element is new head
272 * or not */
273 if (it == pfq.begin() && dpp <= *it)
274 it++;
275 pfq.insert(it, dpp);
276 }
277
278 return pf_pkt;
279}