queued.cc revision 12727:56c23b54bcb1 
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->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}
285