base.cc revision 10318:98771a936b61 
1/*
2 * Copyright (c) 2013 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 * Copyright (c) 2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ron Dreslinski
41 */
42
43/**
44 * @file
45 * Hardware Prefetcher Definition.
46 */
47
48#include <list>
49
50#include "arch/isa_traits.hh"
51#include "base/trace.hh"
52#include "config/the_isa.hh"
53#include "debug/HWPrefetch.hh"
54#include "mem/cache/prefetch/base.hh"
55#include "mem/cache/base.hh"
56#include "mem/request.hh"
57#include "sim/system.hh"
58
59BasePrefetcher::BasePrefetcher(const Params *p)
60    : ClockedObject(p), size(p->size), latency(p->latency), degree(p->degree),
61      useMasterId(p->use_master_id), pageStop(!p->cross_pages),
62      serialSquash(p->serial_squash), onlyData(p->data_accesses_only),
63      onMissOnly(p->on_miss_only), onReadOnly(p->on_read_only),
64      onPrefetch(p->on_prefetch), system(p->sys),
65      masterId(system->getMasterId(name()))
66{
67}
68
69void
70BasePrefetcher::setCache(BaseCache *_cache)
71{
72    cache = _cache;
73    blkSize = cache->getBlockSize();
74}
75
76void
77BasePrefetcher::regStats()
78{
79    pfIdentified
80        .name(name() + ".prefetcher.num_hwpf_identified")
81        .desc("number of hwpf identified")
82        ;
83
84    pfMSHRHit
85        .name(name() + ".prefetcher.num_hwpf_already_in_mshr")
86        .desc("number of hwpf that were already in mshr")
87        ;
88
89    pfCacheHit
90        .name(name() + ".prefetcher.num_hwpf_already_in_cache")
91        .desc("number of hwpf that were already in the cache")
92        ;
93
94    pfBufferHit
95        .name(name() + ".prefetcher.num_hwpf_already_in_prefetcher")
96        .desc("number of hwpf that were already in the prefetch queue")
97        ;
98
99    pfRemovedFull
100        .name(name() + ".prefetcher.num_hwpf_evicted")
101        .desc("number of hwpf removed due to no buffer left")
102        ;
103
104    pfRemovedMSHR
105        .name(name() + ".prefetcher.num_hwpf_removed_MSHR_hit")
106        .desc("number of hwpf removed because MSHR allocated")
107        ;
108
109    pfIssued
110        .name(name() + ".prefetcher.num_hwpf_issued")
111        .desc("number of hwpf issued")
112        ;
113
114    pfSpanPage
115        .name(name() + ".prefetcher.num_hwpf_span_page")
116        .desc("number of hwpf spanning a virtual page")
117        ;
118
119    pfSquashed
120        .name(name() + ".prefetcher.num_hwpf_squashed_from_miss")
121        .desc("number of hwpf that got squashed due to a miss "
122              "aborting calculation time")
123        ;
124}
125
126inline bool
127BasePrefetcher::inCache(Addr addr, bool is_secure)
128{
129    if (cache->inCache(addr, is_secure)) {
130        pfCacheHit++;
131        return true;
132    }
133    return false;
134}
135
136inline bool
137BasePrefetcher::inMissQueue(Addr addr, bool is_secure)
138{
139    if (cache->inMissQueue(addr, is_secure)) {
140        pfMSHRHit++;
141        return true;
142    }
143    return false;
144}
145
146PacketPtr
147BasePrefetcher::getPacket()
148{
149    DPRINTF(HWPrefetch, "Requesting a hw_pf to issue\n");
150
151    if (pf.empty()) {
152        DPRINTF(HWPrefetch, "No HW_PF found\n");
153        return NULL;
154    }
155
156    PacketPtr pkt = pf.begin()->pkt;
157    while (!pf.empty()) {
158        pkt = pf.begin()->pkt;
159        pf.pop_front();
160
161        Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize-1);
162        bool is_secure = pkt->isSecure();
163
164        if (!inCache(blk_addr, is_secure) && !inMissQueue(blk_addr, is_secure))
165            // we found a prefetch, return it
166            break;
167
168        DPRINTF(HWPrefetch, "addr 0x%x (%s) in cache, skipping\n",
169                pkt->getAddr(), is_secure ? "s" : "ns");
170        delete pkt->req;
171        delete pkt;
172
173        if (pf.empty()) {
174            cache->deassertMemSideBusRequest(BaseCache::Request_PF);
175            return NULL; // None left, all were in cache
176        }
177    }
178
179    pfIssued++;
180    assert(pkt != NULL);
181    DPRINTF(HWPrefetch, "returning 0x%x (%s)\n", pkt->getAddr(),
182            pkt->isSecure() ? "s" : "ns");
183    return pkt;
184}
185
186
187Tick
188BasePrefetcher::notify(PacketPtr &pkt, Tick tick)
189{
190    // Don't consult the prefetcher if any of the following conditons are true
191    // 1) The request is uncacheable
192    // 2) The request is a fetch, but we are only prefeching data
193    // 3) The request is a cache hit, but we are only training on misses
194    // 4) THe request is a write, but we are only training on reads
195    if (!pkt->req->isUncacheable() && !(pkt->req->isInstFetch() && onlyData) &&
196        !(onMissOnly && inCache(pkt->getAddr(), true)) &&
197        !(onReadOnly && !pkt->isRead())) {
198        // Calculate the blk address
199        Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize-1);
200        bool is_secure = pkt->isSecure();
201
202        // Check if miss is in pfq, if so remove it
203        std::list<DeferredPacket>::iterator iter = inPrefetch(blk_addr,
204                                                              is_secure);
205        if (iter != pf.end()) {
206            DPRINTF(HWPrefetch, "Saw a miss to a queued prefetch addr: "
207                    "0x%x (%s), removing it\n", blk_addr,
208                    is_secure ? "s" : "ns");
209            pfRemovedMSHR++;
210            delete iter->pkt->req;
211            delete iter->pkt;
212            iter = pf.erase(iter);
213            if (pf.empty())
214                cache->deassertMemSideBusRequest(BaseCache::Request_PF);
215        }
216
217        // Remove anything in queue with delay older than time
218        // since everything is inserted in time order, start from end
219        // and work until pf.empty() or time is earlier
220        // This is done to emulate Aborting the previous work on a new miss
221        // Needed for serial calculators like GHB
222        if (serialSquash) {
223            iter = pf.end();
224            if (iter != pf.begin())
225                iter--;
226            while (!pf.empty() && iter->tick >= tick) {
227                pfSquashed++;
228                DPRINTF(HWPrefetch, "Squashing old prefetch addr: 0x%x\n",
229                        iter->pkt->getAddr());
230                delete iter->pkt->req;
231                delete iter->pkt;
232                iter = pf.erase(iter);
233                if (iter != pf.begin())
234                    iter--;
235            }
236            if (pf.empty())
237                cache->deassertMemSideBusRequest(BaseCache::Request_PF);
238        }
239
240
241        std::list<Addr> addresses;
242        std::list<Cycles> delays;
243        calculatePrefetch(pkt, addresses, delays);
244
245        std::list<Addr>::iterator addrIter = addresses.begin();
246        std::list<Cycles>::iterator delayIter = delays.begin();
247        for (; addrIter != addresses.end(); ++addrIter, ++delayIter) {
248            Addr addr = *addrIter;
249
250            pfIdentified++;
251
252            DPRINTF(HWPrefetch, "Found a pf candidate addr: 0x%x, "
253                    "inserting into prefetch queue with delay %d time %d\n",
254                    addr, *delayIter, time);
255
256            // Check if it is already in the pf buffer
257            if (inPrefetch(addr, is_secure) != pf.end()) {
258                pfBufferHit++;
259                DPRINTF(HWPrefetch, "Prefetch addr already in pf buffer\n");
260                continue;
261            }
262
263            // create a prefetch memreq
264            Request *prefetchReq = new Request(*addrIter, blkSize, 0, masterId);
265            if (is_secure)
266                prefetchReq->setFlags(Request::SECURE);
267            prefetchReq->taskId(ContextSwitchTaskId::Prefetcher);
268            PacketPtr prefetch =
269                new Packet(prefetchReq, MemCmd::HardPFReq);
270            prefetch->allocate();
271            prefetch->req->setThreadContext(pkt->req->contextId(),
272                                            pkt->req->threadId());
273
274            // Tag orefetch reqeuests with corresponding PC to train lower
275            // cache-level prefetchers
276            if (onPrefetch && pkt->req->hasPC())
277                prefetch->req->setPC(pkt->req->getPC());
278
279            // We just remove the head if we are full
280            if (pf.size() == size) {
281                pfRemovedFull++;
282                PacketPtr old_pkt = pf.begin()->pkt;
283                DPRINTF(HWPrefetch, "Prefetch queue full, "
284                        "removing oldest 0x%x\n", old_pkt->getAddr());
285                delete old_pkt->req;
286                delete old_pkt;
287                pf.pop_front();
288            }
289
290            pf.push_back(DeferredPacket(tick + clockPeriod() * *delayIter,
291                                        prefetch));
292        }
293    }
294
295    return pf.empty() ? 0 : pf.front().tick;
296}
297
298std::list<BasePrefetcher::DeferredPacket>::iterator
299BasePrefetcher::inPrefetch(Addr address, bool is_secure)
300{
301    // Guaranteed to only be one match, we always check before inserting
302    std::list<DeferredPacket>::iterator iter;
303    for (iter = pf.begin(); iter != pf.end(); iter++) {
304        if (((*iter).pkt->getAddr() & ~(Addr)(blkSize-1)) == address &&
305            (*iter).pkt->isSecure() == is_secure) {
306            return iter;
307        }
308    }
309    return pf.end();
310}
311
312bool
313BasePrefetcher::samePage(Addr a, Addr b)
314{
315    return roundDown(a, TheISA::PageBytes) == roundDown(b, TheISA::PageBytes);
316}
317
318
319