queued.cc revision 11435:0f1b46dde3fa 
1/*
2 * Copyright (c) 2014 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->getAddr() & ~(Addr)(blkSize - 1);
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<Addr> addresses;
86        calculatePrefetch(pkt, addresses);
87
88        // Queue up generated prefetches
89        for (Addr pf_addr : addresses) {
90
91            // Block align prefetch address
92            pf_addr = pf_addr & ~(Addr)(blkSize - 1);
93
94            pfIdentified++;
95            DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
96                    "inserting into prefetch queue.\n", pf_addr);
97
98            if (queueFilter && inPrefetch(pf_addr, is_secure)) {
99                pfBufferHit++;
100                DPRINTF(HWPrefetch, "Prefetch addr already in "
101                        "prefetch queue\n");
102                continue;
103            }
104
105            if (cacheSnoop && (inCache(pf_addr, is_secure) ||
106                        inMissQueue(pf_addr, is_secure))) {
107                pfInCache++;
108                DPRINTF(HWPrefetch, "Dropping redundant in "
109                        "cache/MSHR prefetch addr:%#x\n", pf_addr);
110                continue;
111            }
112
113            // Create a prefetch memory request
114            Request *pf_req =
115                new Request(pf_addr, blkSize, 0, masterId);
116
117            if (is_secure) {
118                pf_req->setFlags(Request::SECURE);
119            }
120            pf_req->taskId(ContextSwitchTaskId::Prefetcher);
121            PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
122            pf_pkt->allocate();
123
124            if (pkt->req->hasContextId()) {
125                pf_req->setContext(pkt->req->contextId());
126            }
127
128            if (tagPrefetch && pkt->req->hasPC()) {
129                // Tag prefetch packet with  accessing pc
130                pf_pkt->req->setPC(pkt->req->getPC());
131            }
132
133            // Verify prefetch buffer space for request
134            if (pfq.size() == queueSize) {
135                pfRemovedFull++;
136                PacketPtr old_pkt = pfq.begin()->pkt;
137                DPRINTF(HWPrefetch, "Prefetch queue full, removing "
138                        "oldest packet addr: %#x", old_pkt->getAddr());
139                delete old_pkt->req;
140                delete old_pkt;
141                pfq.pop_front();
142            }
143
144            Tick pf_time = curTick() + clockPeriod() * latency;
145            DPRINTF(HWPrefetch, "Prefetch queued. "
146                    "addr:%#x tick:%lld.\n", pf_addr, pf_time);
147
148            pfq.emplace_back(pf_time, pf_pkt);
149        }
150    }
151
152    return pfq.empty() ? MaxTick : pfq.front().tick;
153}
154
155PacketPtr
156QueuedPrefetcher::getPacket()
157{
158    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
159
160    if (pfq.empty()) {
161        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
162        return NULL;
163    }
164
165    PacketPtr pkt = pfq.begin()->pkt;
166    pfq.pop_front();
167
168    pfIssued++;
169    assert(pkt != NULL);
170    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
171    return pkt;
172}
173
174bool
175QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
176{
177    for (const DeferredPacket &dp : pfq) {
178        if (dp.pkt->getAddr() == address &&
179            dp.pkt->isSecure() == is_secure) return true;
180    }
181
182    return false;
183}
184
185void
186QueuedPrefetcher::regStats()
187{
188    BasePrefetcher::regStats();
189
190    pfIdentified
191        .name(name() + ".pfIdentified")
192        .desc("number of prefetch candidates identified");
193
194    pfBufferHit
195        .name(name() + ".pfBufferHit")
196        .desc("number of redundant prefetches already in prefetch queue");
197
198    pfInCache
199        .name(name() + ".pfInCache")
200        .desc("number of redundant prefetches already in cache/mshr dropped");
201
202    pfRemovedFull
203        .name(name() + ".pfRemovedFull")
204        .desc("number of prefetches dropped due to prefetch queue size");
205
206    pfSpanPage
207        .name(name() + ".pfSpanPage")
208        .desc("number of prefetches not generated due to page crossing");
209}
210