1/*
2 * Copyright (c) 2005 The Regents of The University of Michigan
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 * Authors: Ron Dreslinski
29 */
30
31/**
32 * @file
33 * Hardware Prefetcher Definition.
34 */
35
36#include <list>
37
38#include "arch/isa_traits.hh"
39#include "base/trace.hh"
40#include "config/the_isa.hh"
41#include "mem/cache/prefetch/base.hh"
42#include "mem/cache/base.hh"
43#include "mem/request.hh"
44
45BasePrefetcher::BasePrefetcher(const BaseCacheParams *p)
46 : size(p->prefetcher_size), pageStop(!p->prefetch_past_page),
47 serialSquash(p->prefetch_serial_squash),
48 onlyData(p->prefetch_data_accesses_only)
49{
50}
51
52void
53BasePrefetcher::setCache(BaseCache *_cache)
54{
55 cache = _cache;
56 blkSize = cache->getBlockSize();
57 _name = cache->name() + "-pf";
58}
59
60void
61BasePrefetcher::regStats(const std::string &name)
62{
63 pfIdentified
64 .name(name + ".prefetcher.num_hwpf_identified")
65 .desc("number of hwpf identified")
66 ;
67
68 pfMSHRHit
69 .name(name + ".prefetcher.num_hwpf_already_in_mshr")
70 .desc("number of hwpf that were already in mshr")
71 ;
72
73 pfCacheHit
74 .name(name + ".prefetcher.num_hwpf_already_in_cache")
75 .desc("number of hwpf that were already in the cache")
76 ;
77
78 pfBufferHit
79 .name(name + ".prefetcher.num_hwpf_already_in_prefetcher")
80 .desc("number of hwpf that were already in the prefetch queue")
81 ;
82
83 pfRemovedFull
84 .name(name + ".prefetcher.num_hwpf_evicted")
85 .desc("number of hwpf removed due to no buffer left")
86 ;
87
88 pfRemovedMSHR
89 .name(name + ".prefetcher.num_hwpf_removed_MSHR_hit")
90 .desc("number of hwpf removed because MSHR allocated")
91 ;
92
93 pfIssued
94 .name(name + ".prefetcher.num_hwpf_issued")
95 .desc("number of hwpf issued")
96 ;
97
98 pfSpanPage
99 .name(name + ".prefetcher.num_hwpf_span_page")
100 .desc("number of hwpf spanning a virtual page")
101 ;
102
103 pfSquashed
104 .name(name + ".prefetcher.num_hwpf_squashed_from_miss")
105 .desc("number of hwpf that got squashed due to a miss "
106 "aborting calculation time")
107 ;
108}
109
110inline bool
111BasePrefetcher::inCache(Addr addr)
112{
113 if (cache->inCache(addr)) {
114 pfCacheHit++;
115 return true;
116 }
117 return false;
118}
119
120inline bool
121BasePrefetcher::inMissQueue(Addr addr)
122{
123 if (cache->inMissQueue(addr)) {
124 pfMSHRHit++;
125 return true;
126 }
127 return false;
128}
129
130PacketPtr
131BasePrefetcher::getPacket()
132{
133 DPRINTF(HWPrefetch, "Requesting a hw_pf to issue\n");
134
135 if (pf.empty()) {
136 DPRINTF(HWPrefetch, "No HW_PF found\n");
137 return NULL;
138 }
139
140 PacketPtr pkt;
141 bool keep_trying = false;
142 do {
143 pkt = *pf.begin();
144 pf.pop_front();
145
146 if (keep_trying) {
147 DPRINTF(HWPrefetch, "addr 0x%x in cache, skipping\n",
148 pkt->getAddr());
149 delete pkt->req;
150 delete pkt;
151 }
152
153 if (pf.empty()) {
154 cache->deassertMemSideBusRequest(BaseCache::Request_PF);
155 if (keep_trying) {
156 return NULL; // None left, all were in cache
157 }
158 }
159 } while (keep_trying);
160
161 pfIssued++;
162 assert(pkt != NULL);
163 DPRINTF(HWPrefetch, "returning 0x%x\n", pkt->getAddr());
164 return pkt;
165}
166
167
168Tick
169BasePrefetcher::notify(PacketPtr &pkt, Tick time)
170{
171 if (!pkt->req->isUncacheable() && !(pkt->req->isInstFetch() && onlyData)) {
172 // Calculate the blk address
173 Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize-1);
174
175 // Check if miss is in pfq, if so remove it
176 std::list<PacketPtr>::iterator iter = inPrefetch(blk_addr);
177 if (iter != pf.end()) {
178 DPRINTF(HWPrefetch, "Saw a miss to a queued prefetch addr: "
179 "0x%x, removing it\n", blk_addr);
180 pfRemovedMSHR++;
181 delete (*iter)->req;
182 delete (*iter);
183 pf.erase(iter);
184 if (pf.empty())
185 cache->deassertMemSideBusRequest(BaseCache::Request_PF);
186 }
187
188 // Remove anything in queue with delay older than time
189 // since everything is inserted in time order, start from end
190 // and work until pf.empty() or time is earlier
191 // This is done to emulate Aborting the previous work on a new miss
192 // Needed for serial calculators like GHB
193 if (serialSquash) {
194 iter = pf.end();
195 iter--;
196 while (!pf.empty() && ((*iter)->time >= time)) {
197 pfSquashed++;
198 DPRINTF(HWPrefetch, "Squashing old prefetch addr: 0x%x\n",
199 (*iter)->getAddr());
200 delete (*iter)->req;
201 delete (*iter);
202 pf.erase(iter);
203 iter--;
204 }
205 if (pf.empty())
206 cache->deassertMemSideBusRequest(BaseCache::Request_PF);
207 }
208
209
210 std::list<Addr> addresses;
211 std::list<Tick> delays;
212 calculatePrefetch(pkt, addresses, delays);
213
214 std::list<Addr>::iterator addrIter = addresses.begin();
215 std::list<Tick>::iterator delayIter = delays.begin();
216 for (; addrIter != addresses.end(); ++addrIter, ++delayIter) {
217 Addr addr = *addrIter;
218
219 pfIdentified++;
220
221 DPRINTF(HWPrefetch, "Found a pf candidate addr: 0x%x, "
222 "inserting into prefetch queue with delay %d time %d\n",
223 addr, *delayIter, time);
224
225 // Check if it is already in the pf buffer
226 if (inPrefetch(addr) != pf.end()) {
227 pfBufferHit++;
228 DPRINTF(HWPrefetch, "Prefetch addr already in pf buffer\n");
229 continue;
230 }
231
232 // create a prefetch memreq
233 Request *prefetchReq = new Request(*addrIter, blkSize, 0);
234 PacketPtr prefetch =
235 new Packet(prefetchReq, MemCmd::HardPFReq, Packet::Broadcast);
236 prefetch->allocate();
237 prefetch->req->setThreadContext(pkt->req->contextId(),
238 pkt->req->threadId());
239
240 prefetch->time = time + (*delayIter); // @todo ADD LATENCY HERE
241
242 // We just remove the head if we are full
243 if (pf.size() == size) {
244 pfRemovedFull++;
245 PacketPtr old_pkt = *pf.begin();
246 DPRINTF(HWPrefetch, "Prefetch queue full, "
247 "removing oldest 0x%x\n", old_pkt->getAddr());
248 delete old_pkt->req;
249 delete old_pkt;
250 pf.pop_front();
251 }
252
253 pf.push_back(prefetch);
254 }
255 }
256
257 return pf.empty() ? 0 : pf.front()->time;
258}
259
260std::list<PacketPtr>::iterator
261BasePrefetcher::inPrefetch(Addr address)
262{
263 // Guaranteed to only be one match, we always check before inserting
264 std::list<PacketPtr>::iterator iter;
265 for (iter = pf.begin(); iter != pf.end(); iter++) {
266 if (((*iter)->getAddr() & ~(Addr)(blkSize-1)) == address) {
267 return iter;
268 }
269 }
270 return pf.end();
271}
272
273bool
274BasePrefetcher::samePage(Addr a, Addr b)
275{
276 return roundDown(a, TheISA::VMPageSize) == roundDown(b, TheISA::VMPageSize);
277}