queued.cc revision 13416:d90887d0c889 
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
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
115PacketPtr
116QueuedPrefetcher::getPacket()
117{
118    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
119
120    if (pfq.empty()) {
121        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
122        return nullptr;
123    }
124
125    PacketPtr pkt = pfq.begin()->pkt;
126    pfq.pop_front();
127
128    pfIssued++;
129    assert(pkt != nullptr);
130    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
131    return pkt;
132}
133
134std::list<QueuedPrefetcher::DeferredPacket>::const_iterator
135QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
136{
137    for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
138        if ((*dp).pkt->getAddr() == address &&
139            (*dp).pkt->isSecure() == is_secure) return dp;
140    }
141
142    return pfq.end();
143}
144
145QueuedPrefetcher::iterator
146QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
147{
148    for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
149        if (dp->pkt->getAddr() == address &&
150            dp->pkt->isSecure() == is_secure) return dp;
151    }
152
153    return pfq.end();
154}
155
156void
157QueuedPrefetcher::regStats()
158{
159    BasePrefetcher::regStats();
160
161    pfIdentified
162        .name(name() + ".pfIdentified")
163        .desc("number of prefetch candidates identified");
164
165    pfBufferHit
166        .name(name() + ".pfBufferHit")
167        .desc("number of redundant prefetches already in prefetch queue");
168
169    pfInCache
170        .name(name() + ".pfInCache")
171        .desc("number of redundant prefetches already in cache/mshr dropped");
172
173    pfRemovedFull
174        .name(name() + ".pfRemovedFull")
175        .desc("number of prefetches dropped due to prefetch queue size");
176
177    pfSpanPage
178        .name(name() + ".pfSpanPage")
179        .desc("number of prefetches not generated due to page crossing");
180}
181
182PacketPtr
183QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
184{
185    if (queueFilter) {
186        iterator it = inPrefetch(pf_info.first, is_secure);
187        /* If the address is already in the queue, update priority and leave */
188        if (it != pfq.end()) {
189            pfBufferHit++;
190            if (it->priority < pf_info.second) {
191                /* Update priority value and position in the queue */
192                it->priority = pf_info.second;
193                iterator prev = it;
194                bool cont = true;
195                while (cont && prev != pfq.begin()) {
196                    prev--;
197                    /* If the packet has higher priority, swap */
198                    if (*it > *prev) {
199                        std::swap(*it, *prev);
200                        it = prev;
201                    }
202                }
203                DPRINTF(HWPrefetch, "Prefetch addr already in "
204                    "prefetch queue, priority updated\n");
205            } else {
206                DPRINTF(HWPrefetch, "Prefetch addr already in "
207                    "prefetch queue\n");
208            }
209            return nullptr;
210        }
211    }
212
213    if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
214                inMissQueue(pf_info.first, is_secure))) {
215        pfInCache++;
216        DPRINTF(HWPrefetch, "Dropping redundant in "
217                "cache/MSHR prefetch addr:%#x\n", pf_info.first);
218        return nullptr;
219    }
220
221    /* Create a prefetch memory request */
222    RequestPtr pf_req =
223        std::make_shared<Request>(pf_info.first, blkSize, 0, masterId);
224
225    if (is_secure) {
226        pf_req->setFlags(Request::SECURE);
227    }
228    pf_req->taskId(ContextSwitchTaskId::Prefetcher);
229    PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
230    pf_pkt->allocate();
231
232    /* Verify prefetch buffer space for request */
233    if (pfq.size() == queueSize) {
234        pfRemovedFull++;
235        /* Lowest priority packet */
236        iterator it = pfq.end();
237        panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
238        --it;
239        /* Look for oldest in that level of priority */
240        panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
241        iterator prev = it;
242        bool cont = true;
243        /* While not at the head of the queue */
244        while (cont && prev != pfq.begin()) {
245            prev--;
246            /* While at the same level of priority */
247            cont = (*prev).priority == (*it).priority;
248            if (cont)
249                /* update pointer */
250                it = prev;
251        }
252        DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
253                            "oldest packet, addr: %#x", it->pkt->getAddr());
254        delete it->pkt;
255        pfq.erase(it);
256    }
257
258    Tick pf_time = curTick() + clockPeriod() * latency;
259    DPRINTF(HWPrefetch, "Prefetch queued. "
260            "addr:%#x priority: %3d tick:%lld.\n",
261            pf_info.first, pf_info.second, pf_time);
262
263    /* Create the packet and find the spot to insert it */
264    DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
265    if (pfq.size() == 0) {
266        pfq.emplace_back(dpp);
267    } else {
268        iterator it = pfq.end();
269        while (it != pfq.begin() && dpp > *it)
270            --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