queued.cc revision 12749:223c83ed9979 
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
66Tick
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    return pfq.empty() ? MaxTick : pfq.front().tick;
115}
116
117PacketPtr
118QueuedPrefetcher::getPacket()
119{
120    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
121
122    if (pfq.empty()) {
123        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
124        return nullptr;
125    }
126
127    PacketPtr pkt = pfq.begin()->pkt;
128    pfq.pop_front();
129
130    pfIssued++;
131    assert(pkt != nullptr);
132    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
133    return pkt;
134}
135
136std::list<QueuedPrefetcher::DeferredPacket>::const_iterator
137QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
138{
139    for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
140        if ((*dp).pkt->getAddr() == address &&
141            (*dp).pkt->isSecure() == is_secure) return dp;
142    }
143
144    return pfq.end();
145}
146
147QueuedPrefetcher::iterator
148QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
149{
150    for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
151        if (dp->pkt->getAddr() == address &&
152            dp->pkt->isSecure() == is_secure) return dp;
153    }
154
155    return pfq.end();
156}
157
158void
159QueuedPrefetcher::regStats()
160{
161    BasePrefetcher::regStats();
162
163    pfIdentified
164        .name(name() + ".pfIdentified")
165        .desc("number of prefetch candidates identified");
166
167    pfBufferHit
168        .name(name() + ".pfBufferHit")
169        .desc("number of redundant prefetches already in prefetch queue");
170
171    pfInCache
172        .name(name() + ".pfInCache")
173        .desc("number of redundant prefetches already in cache/mshr dropped");
174
175    pfRemovedFull
176        .name(name() + ".pfRemovedFull")
177        .desc("number of prefetches dropped due to prefetch queue size");
178
179    pfSpanPage
180        .name(name() + ".pfSpanPage")
181        .desc("number of prefetches not generated due to page crossing");
182}
183
184PacketPtr
185QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
186{
187    if (queueFilter) {
188        iterator it = inPrefetch(pf_info.first, is_secure);
189        /* If the address is already in the queue, update priority and leave */
190        if (it != pfq.end()) {
191            pfBufferHit++;
192            if (it->priority < pf_info.second) {
193                /* Update priority value and position in the queue */
194                it->priority = pf_info.second;
195                iterator prev = it;
196                bool cont = true;
197                while (cont && prev != pfq.begin()) {
198                    prev--;
199                    /* If the packet has higher priority, swap */
200                    if (*it > *prev) {
201                        std::swap(*it, *prev);
202                        it = prev;
203                    }
204                }
205                DPRINTF(HWPrefetch, "Prefetch addr already in "
206                    "prefetch queue, priority updated\n");
207            } else {
208                DPRINTF(HWPrefetch, "Prefetch addr already in "
209                    "prefetch queue\n");
210            }
211            return nullptr;
212        }
213    }
214
215    if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
216                inMissQueue(pf_info.first, is_secure))) {
217        pfInCache++;
218        DPRINTF(HWPrefetch, "Dropping redundant in "
219                "cache/MSHR prefetch addr:%#x\n", pf_info.first);
220        return nullptr;
221    }
222
223    /* Create a prefetch memory request */
224    RequestPtr pf_req =
225        std::make_shared<Request>(pf_info.first, blkSize, 0, masterId);
226
227    if (is_secure) {
228        pf_req->setFlags(Request::SECURE);
229    }
230    pf_req->taskId(ContextSwitchTaskId::Prefetcher);
231    PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
232    pf_pkt->allocate();
233
234    /* Verify prefetch buffer space for request */
235    if (pfq.size() == queueSize) {
236        pfRemovedFull++;
237        /* Lowest priority packet */
238        iterator it = pfq.end();
239        panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
240        --it;
241        /* Look for oldest in that level of priority */
242        panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
243        iterator prev = it;
244        bool cont = true;
245        /* While not at the head of the queue */
246        while (cont && prev != pfq.begin()) {
247            prev--;
248            /* While at the same level of priority */
249            cont = (*prev).priority == (*it).priority;
250            if (cont)
251                /* update pointer */
252                it = prev;
253        }
254        DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
255                            "oldest packet, addr: %#x", it->pkt->getAddr());
256        delete it->pkt;
257        pfq.erase(it);
258    }
259
260    Tick pf_time = curTick() + clockPeriod() * latency;
261    DPRINTF(HWPrefetch, "Prefetch queued. "
262            "addr:%#x priority: %3d tick:%lld.\n",
263            pf_info.first, pf_info.second, pf_time);
264
265    /* Create the packet and find the spot to insert it */
266    DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
267    if (pfq.size() == 0) {
268        pfq.emplace_back(dpp);
269    } else {
270        iterator it = pfq.end();
271        while (it != pfq.begin() && dpp > *it)
272            --it;
273        /* If we reach the head, we have to see if the new element is new head
274         * or not */
275        if (it == pfq.begin() && dpp <= *it)
276            it++;
277        pfq.insert(it, dpp);
278    }
279
280    return pf_pkt;
281}
282