queued.cc revision 11439:d0368996f1e0 
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}
279