| /* |
| * Copyright (c) 2012-2013, 2015 ARM Limited |
| * All rights reserved |
| * |
| * The license below extends only to copyright in the software and shall |
| * not be construed as granting a license to any other intellectual |
| * property including but not limited to intellectual property relating |
| * to a hardware implementation of the functionality of the software |
| * licensed hereunder. You may use the software subject to the license |
| * terms below provided that you ensure that this notice is replicated |
| * unmodified and in its entirety in all distributions of the software, |
| * modified or unmodified, in source code or in binary form. |
| * |
| * Copyright (c) 2005 The Regents of The University of Michigan |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer; |
| * redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution; |
| * neither the name of the copyright holders nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * Authors: Ron Dreslinski |
| * Steve Reinhardt |
| */ |
| |
| /** |
| * @file |
| * Stride Prefetcher template instantiations. |
| */ |
| |
| #include "mem/cache/prefetch/stride.hh" |
| |
| #include "base/random.hh" |
| #include "base/trace.hh" |
| #include "debug/HWPrefetch.hh" |
| |
| StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p) |
| : QueuedPrefetcher(p), |
| maxConf(p->max_conf), |
| threshConf(p->thresh_conf), |
| minConf(p->min_conf), |
| startConf(p->start_conf), |
| pcTableAssoc(p->table_assoc), |
| pcTableSets(p->table_sets), |
| useMasterId(p->use_master_id), |
| degree(p->degree), |
| pcTable(pcTableAssoc, pcTableSets, name()) |
| { |
| // Don't consult stride prefetcher on instruction accesses |
| onInst = false; |
| |
| assert(isPowerOf2(pcTableSets)); |
| } |
| |
| StridePrefetcher::StrideEntry** |
| StridePrefetcher::PCTable::allocateNewContext(int context) |
| { |
| auto res = entries.insert(std::make_pair(context, |
| new StrideEntry*[pcTableSets])); |
| auto it = res.first; |
| chatty_assert(res.second, "Allocating an already created context\n"); |
| assert(it->first == context); |
| |
| DPRINTF(HWPrefetch, "Adding context %i with stride entries at %p\n", |
| context, it->second); |
| |
| StrideEntry** entry = it->second; |
| for (int s = 0; s < pcTableSets; s++) { |
| entry[s] = new StrideEntry[pcTableAssoc]; |
| } |
| return entry; |
| } |
| |
| StridePrefetcher::PCTable::~PCTable() { |
| for (auto entry : entries) { |
| for (int s = 0; s < pcTableSets; s++) { |
| delete[] entry.second[s]; |
| } |
| delete[] entry.second; |
| } |
| } |
| |
| void |
| StridePrefetcher::calculatePrefetch(const PacketPtr &pkt, |
| std::vector<AddrPriority> &addresses) |
| { |
| if (!pkt->req->hasPC()) { |
| DPRINTF(HWPrefetch, "Ignoring request with no PC.\n"); |
| return; |
| } |
| |
| // Get required packet info |
| Addr pkt_addr = pkt->getAddr(); |
| Addr pc = pkt->req->getPC(); |
| bool is_secure = pkt->isSecure(); |
| MasterID master_id = useMasterId ? pkt->req->masterId() : 0; |
| |
| // Lookup pc-based information |
| StrideEntry *entry; |
| |
| if (pcTableHit(pc, is_secure, master_id, entry)) { |
| // Hit in table |
| int new_stride = pkt_addr - entry->lastAddr; |
| bool stride_match = (new_stride == entry->stride); |
| |
| // Adjust confidence for stride entry |
| if (stride_match && new_stride != 0) { |
| if (entry->confidence < maxConf) |
| entry->confidence++; |
| } else { |
| if (entry->confidence > minConf) |
| entry->confidence--; |
| // If confidence has dropped below the threshold, train new stride |
| if (entry->confidence < threshConf) |
| entry->stride = new_stride; |
| } |
| |
| DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), " |
| "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride, |
| stride_match ? "match" : "change", |
| entry->confidence); |
| |
| entry->lastAddr = pkt_addr; |
| |
| // Abort prefetch generation if below confidence threshold |
| if (entry->confidence < threshConf) |
| return; |
| |
| // Generate up to degree prefetches |
| for (int d = 1; d <= degree; d++) { |
| // Round strides up to atleast 1 cacheline |
| int prefetch_stride = new_stride; |
| if (abs(new_stride) < blkSize) { |
| prefetch_stride = (new_stride < 0) ? -blkSize : blkSize; |
| } |
| |
| Addr new_addr = pkt_addr + d * prefetch_stride; |
| if (samePage(pkt_addr, new_addr)) { |
| DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr); |
| addresses.push_back(AddrPriority(new_addr, 0)); |
| } else { |
| // Record the number of page crossing prefetches generated |
| pfSpanPage += degree - d + 1; |
| DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n"); |
| return; |
| } |
| } |
| } else { |
| // Miss in table |
| DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr, |
| is_secure ? "s" : "ns"); |
| |
| StrideEntry* entry = pcTableVictim(pc, master_id); |
| entry->instAddr = pc; |
| entry->lastAddr = pkt_addr; |
| entry->isSecure= is_secure; |
| entry->stride = 0; |
| entry->confidence = startConf; |
| } |
| } |
| |
| inline Addr |
| StridePrefetcher::pcHash(Addr pc) const |
| { |
| Addr hash1 = pc >> 1; |
| Addr hash2 = hash1 >> floorLog2(pcTableSets); |
| return (hash1 ^ hash2) & (Addr)(pcTableSets - 1); |
| } |
| |
| inline StridePrefetcher::StrideEntry* |
| StridePrefetcher::pcTableVictim(Addr pc, int master_id) |
| { |
| // Rand replacement for now |
| int set = pcHash(pc); |
| int way = random_mt.random<int>(0, pcTableAssoc - 1); |
| |
| DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way); |
| return &pcTable[master_id][set][way]; |
| } |
| |
| inline bool |
| StridePrefetcher::pcTableHit(Addr pc, bool is_secure, int master_id, |
| StrideEntry* &entry) |
| { |
| int set = pcHash(pc); |
| StrideEntry* set_entries = pcTable[master_id][set]; |
| for (int way = 0; way < pcTableAssoc; way++) { |
| // Search ways for match |
| if (set_entries[way].instAddr == pc && |
| set_entries[way].isSecure == is_secure) { |
| DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way); |
| entry = &set_entries[way]; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| StridePrefetcher* |
| StridePrefetcherParams::create() |
| { |
| return new StridePrefetcher(this); |
| } |
