queued.cc revision 13551:f352df8e2863 
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, const PrefetchInfo &pfi)
68{
69    Addr blk_addr = blockAddress(pfi.getAddr());
70    bool is_secure = pfi.isSecure();
71
72    // Squash queued prefetches if demand miss to same line
73    if (queueSquash) {
74        auto itr = pfq.begin();
75        while (itr != pfq.end()) {
76            if (itr->pfInfo.getAddr() == blk_addr &&
77                itr->pfInfo.isSecure() == is_secure) {
78                delete itr->pkt;
79                itr = pfq.erase(itr);
80            } else {
81                ++itr;
82            }
83        }
84    }
85
86    // Calculate prefetches given this access
87    std::vector<AddrPriority> addresses;
88    calculatePrefetch(pfi, addresses);
89
90    // Queue up generated prefetches
91    for (AddrPriority& addr_prio : addresses) {
92
93        // Block align prefetch address
94        addr_prio.first = blockAddress(addr_prio.first);
95
96        PrefetchInfo new_pfi(pfi,addr_prio.first);
97
98        pfIdentified++;
99        DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
100                "inserting into prefetch queue.\n", new_pfi.getAddr());
101
102        // Create and insert the request
103        insert(pkt, new_pfi, addr_prio.second);
104    }
105}
106
107PacketPtr
108QueuedPrefetcher::getPacket()
109{
110    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
111
112    if (pfq.empty()) {
113        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
114        return nullptr;
115    }
116
117    PacketPtr pkt = pfq.front().pkt;
118    pfq.pop_front();
119
120    pfIssued++;
121    assert(pkt != nullptr);
122    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
123    return pkt;
124}
125
126QueuedPrefetcher::const_iterator
127QueuedPrefetcher::inPrefetch(const PrefetchInfo &pfi) const
128{
129    for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
130        if (dp->pfInfo.sameAddr(pfi)) return dp;
131    }
132
133    return pfq.end();
134}
135
136QueuedPrefetcher::iterator
137QueuedPrefetcher::inPrefetch(const PrefetchInfo &pfi)
138{
139    for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
140        if (dp->pfInfo.sameAddr(pfi)) return dp;
141    }
142
143    return pfq.end();
144}
145
146void
147QueuedPrefetcher::regStats()
148{
149    BasePrefetcher::regStats();
150
151    pfIdentified
152        .name(name() + ".pfIdentified")
153        .desc("number of prefetch candidates identified");
154
155    pfBufferHit
156        .name(name() + ".pfBufferHit")
157        .desc("number of redundant prefetches already in prefetch queue");
158
159    pfInCache
160        .name(name() + ".pfInCache")
161        .desc("number of redundant prefetches already in cache/mshr dropped");
162
163    pfRemovedFull
164        .name(name() + ".pfRemovedFull")
165        .desc("number of prefetches dropped due to prefetch queue size");
166
167    pfSpanPage
168        .name(name() + ".pfSpanPage")
169        .desc("number of prefetches not generated due to page crossing");
170}
171
172void
173QueuedPrefetcher::insert(const PacketPtr &pkt, PrefetchInfo &new_pfi,
174                         int32_t priority)
175{
176    if (queueFilter) {
177        iterator it = inPrefetch(new_pfi);
178        /* If the address is already in the queue, update priority and leave */
179        if (it != pfq.end()) {
180            pfBufferHit++;
181            if (it->priority < priority) {
182                /* Update priority value and position in the queue */
183                it->priority = priority;
184                iterator prev = it;
185                bool cont = true;
186                while (cont && prev != pfq.begin()) {
187                    prev--;
188                    /* If the packet has higher priority, swap */
189                    if (*it > *prev) {
190                        std::swap(*it, *prev);
191                        it = prev;
192                    }
193                }
194                DPRINTF(HWPrefetch, "Prefetch addr already in "
195                    "prefetch queue, priority updated\n");
196            } else {
197                DPRINTF(HWPrefetch, "Prefetch addr already in "
198                    "prefetch queue\n");
199            }
200            return;
201        }
202    }
203
204    Addr target_addr = new_pfi.getAddr();
205    if (useVirtualAddresses) {
206        assert(pkt->req->hasPaddr());
207        //if we trained with virtual addresses, compute the phsysical address
208        if (new_pfi.getAddr() >= pkt->req->getVaddr()) {
209            //positive stride
210            target_addr = pkt->req->getPaddr() +
211                (new_pfi.getAddr() - pkt->req->getVaddr());
212        } else {
213            //negative stride
214            target_addr = pkt->req->getPaddr() -
215                (pkt->req->getVaddr() - new_pfi.getAddr());
216        }
217    }
218
219    if (cacheSnoop && (inCache(target_addr, new_pfi.isSecure()) ||
220                inMissQueue(target_addr, new_pfi.isSecure()))) {
221        pfInCache++;
222        DPRINTF(HWPrefetch, "Dropping redundant in "
223                "cache/MSHR prefetch addr:%#x\n", target_addr);
224        return;
225    }
226
227    /* Create a prefetch memory request */
228    RequestPtr pf_req =
229        std::make_shared<Request>(target_addr, blkSize, 0, masterId);
230
231    if (new_pfi.isSecure()) {
232        pf_req->setFlags(Request::SECURE);
233    }
234    pf_req->taskId(ContextSwitchTaskId::Prefetcher);
235    PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
236    pf_pkt->allocate();
237    if (tagPrefetch && new_pfi.hasPC()) {
238        // Tag prefetch packet with  accessing pc
239        pf_pkt->req->setPC(new_pfi.getPC());
240    }
241
242    /* Verify prefetch buffer space for request */
243    if (pfq.size() == queueSize) {
244        pfRemovedFull++;
245        /* Lowest priority packet */
246        iterator it = pfq.end();
247        panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
248        --it;
249        /* Look for oldest in that level of priority */
250        panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
251        iterator prev = it;
252        bool cont = true;
253        /* While not at the head of the queue */
254        while (cont && prev != pfq.begin()) {
255            prev--;
256            /* While at the same level of priority */
257            cont = prev->priority == it->priority;
258            if (cont)
259                /* update pointer */
260                it = prev;
261        }
262        DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
263                            "oldest packet, addr: %#x", it->pfInfo.getAddr());
264        delete it->pkt;
265        pfq.erase(it);
266    }
267
268    Tick pf_time = curTick() + clockPeriod() * latency;
269    DPRINTF(HWPrefetch, "Prefetch queued. "
270            "addr:%#x priority: %3d tick:%lld.\n",
271            target_addr, priority, pf_time);
272
273    /* Create the packet and find the spot to insert it */
274    DeferredPacket dpp(new_pfi, pf_time, pf_pkt, priority);
275    if (pfq.size() == 0) {
276        pfq.emplace_back(dpp);
277    } else {
278        iterator it = pfq.end();
279        do {
280            --it;
281        } while (it != pfq.begin() && dpp > *it);
282        /* If we reach the head, we have to see if the new element is new head
283         * or not */
284        if (it == pfq.begin() && dpp <= *it)
285            it++;
286        pfq.insert(it, dpp);
287    }
288}
289