queued.cc revision 13428:ceddb3964aea 
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            // Block align prefetch address
95            pf_info.first = blockAddress(pf_info.first);
96
97            pfIdentified++;
98            DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
99                    "inserting into prefetch queue.\n", pf_info.first);
100
101            // Create and insert the request
102            PacketPtr pf_pkt = insert(pf_info, is_secure);
103
104            if (pf_pkt != nullptr) {
105                if (tagPrefetch && pkt->req->hasPC()) {
106                    // Tag prefetch packet with  accessing pc
107                    pf_pkt->req->setPC(pkt->req->getPC());
108                }
109            }
110        }
111    }
112}
113
114PacketPtr
115QueuedPrefetcher::getPacket()
116{
117    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
118
119    if (pfq.empty()) {
120        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
121        return nullptr;
122    }
123
124    PacketPtr pkt = pfq.begin()->pkt;
125    pfq.pop_front();
126
127    pfIssued++;
128    assert(pkt != nullptr);
129    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
130    return pkt;
131}
132
133QueuedPrefetcher::const_iterator
134QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
135{
136    for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
137        if ((*dp).pkt->getAddr() == address &&
138            (*dp).pkt->isSecure() == is_secure) return dp;
139    }
140
141    return pfq.end();
142}
143
144QueuedPrefetcher::iterator
145QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
146{
147    for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
148        if (dp->pkt->getAddr() == address &&
149            dp->pkt->isSecure() == is_secure) return dp;
150    }
151
152    return pfq.end();
153}
154
155void
156QueuedPrefetcher::regStats()
157{
158    BasePrefetcher::regStats();
159
160    pfIdentified
161        .name(name() + ".pfIdentified")
162        .desc("number of prefetch candidates identified");
163
164    pfBufferHit
165        .name(name() + ".pfBufferHit")
166        .desc("number of redundant prefetches already in prefetch queue");
167
168    pfInCache
169        .name(name() + ".pfInCache")
170        .desc("number of redundant prefetches already in cache/mshr dropped");
171
172    pfRemovedFull
173        .name(name() + ".pfRemovedFull")
174        .desc("number of prefetches dropped due to prefetch queue size");
175
176    pfSpanPage
177        .name(name() + ".pfSpanPage")
178        .desc("number of prefetches not generated due to page crossing");
179}
180
181PacketPtr
182QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
183{
184    if (queueFilter) {
185        iterator it = inPrefetch(pf_info.first, is_secure);
186        /* If the address is already in the queue, update priority and leave */
187        if (it != pfq.end()) {
188            pfBufferHit++;
189            if (it->priority < pf_info.second) {
190                /* Update priority value and position in the queue */
191                it->priority = pf_info.second;
192                iterator prev = it;
193                bool cont = true;
194                while (cont && prev != pfq.begin()) {
195                    prev--;
196                    /* If the packet has higher priority, swap */
197                    if (*it > *prev) {
198                        std::swap(*it, *prev);
199                        it = prev;
200                    }
201                }
202                DPRINTF(HWPrefetch, "Prefetch addr already in "
203                    "prefetch queue, priority updated\n");
204            } else {
205                DPRINTF(HWPrefetch, "Prefetch addr already in "
206                    "prefetch queue\n");
207            }
208            return nullptr;
209        }
210    }
211
212    if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
213                inMissQueue(pf_info.first, is_secure))) {
214        pfInCache++;
215        DPRINTF(HWPrefetch, "Dropping redundant in "
216                "cache/MSHR prefetch addr:%#x\n", pf_info.first);
217        return nullptr;
218    }
219
220    /* Create a prefetch memory request */
221    RequestPtr pf_req =
222        std::make_shared<Request>(pf_info.first, blkSize, 0, masterId);
223
224    if (is_secure) {
225        pf_req->setFlags(Request::SECURE);
226    }
227    pf_req->taskId(ContextSwitchTaskId::Prefetcher);
228    PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
229    pf_pkt->allocate();
230
231    /* Verify prefetch buffer space for request */
232    if (pfq.size() == queueSize) {
233        pfRemovedFull++;
234        /* Lowest priority packet */
235        iterator it = pfq.end();
236        panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
237        --it;
238        /* Look for oldest in that level of priority */
239        panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
240        iterator prev = it;
241        bool cont = true;
242        /* While not at the head of the queue */
243        while (cont && prev != pfq.begin()) {
244            prev--;
245            /* While at the same level of priority */
246            cont = (*prev).priority == (*it).priority;
247            if (cont)
248                /* update pointer */
249                it = prev;
250        }
251        DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
252                            "oldest packet, addr: %#x", it->pkt->getAddr());
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        do {
269            --it;
270        } while (it != pfq.begin() && dpp > *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}
280