base.cc revision 5338:e75d02a09806 
1/*
2 * Copyright (c) 2005 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Ron Dreslinski
29 */
30
31/**
32 * @file
33 * Hardware Prefetcher Definition.
34 */
35
36#include "base/trace.hh"
37#include "mem/cache/base.hh"
38#include "mem/cache/prefetch/base.hh"
39#include "mem/request.hh"
40#include <list>
41
42BasePrefetcher::BasePrefetcher(const BaseCacheParams *p)
43    : size(p->prefetcher_size), pageStop(!p->prefetch_past_page),
44      serialSquash(p->prefetch_serial_squash),
45      cacheCheckPush(p->prefetch_cache_check_push),
46      only_data(p->prefetch_data_accesses_only)
47{
48}
49
50void
51BasePrefetcher::setCache(BaseCache *_cache)
52{
53    cache = _cache;
54    blkSize = cache->getBlockSize();
55}
56
57void
58BasePrefetcher::regStats(const std::string &name)
59{
60    pfIdentified
61        .name(name + ".prefetcher.num_hwpf_identified")
62        .desc("number of hwpf identified")
63        ;
64
65    pfMSHRHit
66        .name(name + ".prefetcher.num_hwpf_already_in_mshr")
67        .desc("number of hwpf that were already in mshr")
68        ;
69
70    pfCacheHit
71        .name(name + ".prefetcher.num_hwpf_already_in_cache")
72        .desc("number of hwpf that were already in the cache")
73        ;
74
75    pfBufferHit
76        .name(name + ".prefetcher.num_hwpf_already_in_prefetcher")
77        .desc("number of hwpf that were already in the prefetch queue")
78        ;
79
80    pfRemovedFull
81        .name(name + ".prefetcher.num_hwpf_evicted")
82        .desc("number of hwpf removed due to no buffer left")
83        ;
84
85    pfRemovedMSHR
86        .name(name + ".prefetcher.num_hwpf_removed_MSHR_hit")
87        .desc("number of hwpf removed because MSHR allocated")
88        ;
89
90    pfIssued
91        .name(name + ".prefetcher.num_hwpf_issued")
92        .desc("number of hwpf issued")
93        ;
94
95    pfSpanPage
96        .name(name + ".prefetcher.num_hwpf_span_page")
97        .desc("number of hwpf spanning a virtual page")
98        ;
99
100    pfSquashed
101        .name(name + ".prefetcher.num_hwpf_squashed_from_miss")
102        .desc("number of hwpf that got squashed due to a miss aborting calculation time")
103        ;
104}
105
106inline bool
107BasePrefetcher::inCache(Addr addr)
108{
109    if (cache->inCache(addr)) {
110        pfCacheHit++;
111        return true;
112    }
113    return false;
114}
115
116inline bool
117BasePrefetcher::inMissQueue(Addr addr)
118{
119    if (cache->inMissQueue(addr)) {
120        pfMSHRHit++;
121        return true;
122    }
123    return false;
124}
125
126PacketPtr
127BasePrefetcher::getPacket()
128{
129    DPRINTF(HWPrefetch, "%s:Requesting a hw_pf to issue\n", cache->name());
130
131    if (pf.empty()) {
132        DPRINTF(HWPrefetch, "%s:No HW_PF found\n", cache->name());
133        return NULL;
134    }
135
136    PacketPtr pkt;
137    bool keepTrying = false;
138    do {
139        pkt = *pf.begin();
140        pf.pop_front();
141        if (!cacheCheckPush) {
142            keepTrying = cache->inCache(pkt->getAddr());
143        }
144        if (pf.empty()) {
145            cache->deassertMemSideBusRequest(BaseCache::Request_PF);
146            if (keepTrying) return NULL; //None left, all were in cache
147        }
148    } while (keepTrying);
149
150    pfIssued++;
151    return pkt;
152}
153
154void
155BasePrefetcher::handleMiss(PacketPtr &pkt, Tick time)
156{
157    if (!pkt->req->isUncacheable() && !(pkt->req->isInstRead() && only_data))
158    {
159        //Calculate the blk address
160        Addr blkAddr = pkt->getAddr() & ~(Addr)(blkSize-1);
161
162        //Check if miss is in pfq, if so remove it
163        std::list<PacketPtr>::iterator iter = inPrefetch(blkAddr);
164        if (iter != pf.end()) {
165            DPRINTF(HWPrefetch, "%s:Saw a miss to a queued prefetch, removing it\n", cache->name());
166            pfRemovedMSHR++;
167            pf.erase(iter);
168            if (pf.empty())
169                cache->deassertMemSideBusRequest(BaseCache::Request_PF);
170        }
171
172        //Remove anything in queue with delay older than time
173        //since everything is inserted in time order, start from end
174        //and work until pf.empty() or time is earlier
175        //This is done to emulate Aborting the previous work on a new miss
176        //Needed for serial calculators like GHB
177        if (serialSquash) {
178            iter = pf.end();
179            iter--;
180            while (!pf.empty() && ((*iter)->time >= time)) {
181                pfSquashed++;
182                pf.pop_back();
183                iter--;
184            }
185            if (pf.empty())
186                cache->deassertMemSideBusRequest(BaseCache::Request_PF);
187        }
188
189
190        std::list<Addr> addresses;
191        std::list<Tick> delays;
192        calculatePrefetch(pkt, addresses, delays);
193
194        std::list<Addr>::iterator addr = addresses.begin();
195        std::list<Tick>::iterator delay = delays.begin();
196        while (addr != addresses.end())
197        {
198            DPRINTF(HWPrefetch, "%s:Found a pf canidate, inserting into prefetch queue\n", cache->name());
199            //temp calc this here...
200            pfIdentified++;
201            //create a prefetch memreq
202            Request * prefetchReq = new Request(*addr, blkSize, 0);
203            PacketPtr prefetch;
204            prefetch = new Packet(prefetchReq, MemCmd::HardPFReq, -1);
205            prefetch->allocate();
206            prefetch->req->setThreadContext(pkt->req->getCpuNum(),
207                                            pkt->req->getThreadNum());
208
209            prefetch->time = time + (*delay); //@todo ADD LATENCY HERE
210            //... initialize
211
212            //Check if it is already in the cache
213            if (cacheCheckPush) {
214                if (cache->inCache(prefetch->getAddr())) {
215                    addr++;
216                    delay++;
217                    continue;
218                }
219            }
220
221            //Check if it is already in the miss_queue
222            if (cache->inMissQueue(prefetch->getAddr())) {
223                addr++;
224                delay++;
225                continue;
226            }
227
228            //Check if it is already in the pf buffer
229            if (inPrefetch(prefetch->getAddr()) != pf.end()) {
230                pfBufferHit++;
231                addr++;
232                delay++;
233                continue;
234            }
235
236            //We just remove the head if we are full
237            if (pf.size() == size)
238            {
239                DPRINTF(HWPrefetch, "%s:Inserting into prefetch queue, it was full removing oldest\n", cache->name());
240                pfRemovedFull++;
241                pf.pop_front();
242            }
243
244            pf.push_back(prefetch);
245
246            //Make sure to request the bus, with proper delay
247            cache->requestMemSideBus(BaseCache::Request_PF, prefetch->time);
248
249            //Increment through the list
250            addr++;
251            delay++;
252        }
253    }
254}
255
256std::list<PacketPtr>::iterator
257BasePrefetcher::inPrefetch(Addr address)
258{
259    //Guaranteed to only be one match, we always check before inserting
260    std::list<PacketPtr>::iterator iter;
261    for (iter=pf.begin(); iter != pf.end(); iter++) {
262        if (((*iter)->getAddr() & ~(Addr)(blkSize-1)) == address) {
263            return iter;
264        }
265    }
266    return pf.end();
267}
268
269
270