blob: ba4c940c1ca851d103d8933fa456025fb4aa8c08 [file] [log] [blame]
/*
* Copyright (c) 2014-2015 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.
*
* 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: Mitch Hayenga
*/
#include "mem/cache/prefetch/queued.hh"
#include <cassert>
#include "base/logging.hh"
#include "base/trace.hh"
#include "debug/HWPrefetch.hh"
#include "mem/request.hh"
#include "params/QueuedPrefetcher.hh"
QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p)
: BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency),
queueSquash(p->queue_squash), queueFilter(p->queue_filter),
cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch)
{
}
QueuedPrefetcher::~QueuedPrefetcher()
{
// Delete the queued prefetch packets
for (DeferredPacket &p : pfq) {
delete p.pkt;
}
}
void
QueuedPrefetcher::notify(const PacketPtr &pkt)
{
// Verify this access type is observed by prefetcher
if (observeAccess(pkt)) {
Addr blk_addr = pkt->getBlockAddr(blkSize);
bool is_secure = pkt->isSecure();
// Squash queued prefetches if demand miss to same line
if (queueSquash) {
auto itr = pfq.begin();
while (itr != pfq.end()) {
if (itr->pkt->getAddr() == blk_addr &&
itr->pkt->isSecure() == is_secure) {
delete itr->pkt;
itr = pfq.erase(itr);
} else {
++itr;
}
}
}
// Calculate prefetches given this access
std::vector<AddrPriority> addresses;
calculatePrefetch(pkt, addresses);
// Queue up generated prefetches
for (AddrPriority& pf_info : addresses) {
// Block align prefetch address
pf_info.first = blockAddress(pf_info.first);
pfIdentified++;
DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
"inserting into prefetch queue.\n", pf_info.first);
// Create and insert the request
PacketPtr pf_pkt = insert(pf_info, is_secure);
if (pf_pkt != nullptr) {
if (tagPrefetch && pkt->req->hasPC()) {
// Tag prefetch packet with accessing pc
pf_pkt->req->setPC(pkt->req->getPC());
}
}
}
}
}
PacketPtr
QueuedPrefetcher::getPacket()
{
DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
if (pfq.empty()) {
DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
return nullptr;
}
PacketPtr pkt = pfq.begin()->pkt;
pfq.pop_front();
pfIssued++;
assert(pkt != nullptr);
DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
return pkt;
}
QueuedPrefetcher::const_iterator
QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
{
for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
if ((*dp).pkt->getAddr() == address &&
(*dp).pkt->isSecure() == is_secure) return dp;
}
return pfq.end();
}
QueuedPrefetcher::iterator
QueuedPrefetcher::inPrefetch(Addr address, bool is_secure)
{
for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) {
if (dp->pkt->getAddr() == address &&
dp->pkt->isSecure() == is_secure) return dp;
}
return pfq.end();
}
void
QueuedPrefetcher::regStats()
{
BasePrefetcher::regStats();
pfIdentified
.name(name() + ".pfIdentified")
.desc("number of prefetch candidates identified");
pfBufferHit
.name(name() + ".pfBufferHit")
.desc("number of redundant prefetches already in prefetch queue");
pfInCache
.name(name() + ".pfInCache")
.desc("number of redundant prefetches already in cache/mshr dropped");
pfRemovedFull
.name(name() + ".pfRemovedFull")
.desc("number of prefetches dropped due to prefetch queue size");
pfSpanPage
.name(name() + ".pfSpanPage")
.desc("number of prefetches not generated due to page crossing");
}
PacketPtr
QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
{
if (queueFilter) {
iterator it = inPrefetch(pf_info.first, is_secure);
/* If the address is already in the queue, update priority and leave */
if (it != pfq.end()) {
pfBufferHit++;
if (it->priority < pf_info.second) {
/* Update priority value and position in the queue */
it->priority = pf_info.second;
iterator prev = it;
bool cont = true;
while (cont && prev != pfq.begin()) {
prev--;
/* If the packet has higher priority, swap */
if (*it > *prev) {
std::swap(*it, *prev);
it = prev;
}
}
DPRINTF(HWPrefetch, "Prefetch addr already in "
"prefetch queue, priority updated\n");
} else {
DPRINTF(HWPrefetch, "Prefetch addr already in "
"prefetch queue\n");
}
return nullptr;
}
}
if (cacheSnoop && (inCache(pf_info.first, is_secure) ||
inMissQueue(pf_info.first, is_secure))) {
pfInCache++;
DPRINTF(HWPrefetch, "Dropping redundant in "
"cache/MSHR prefetch addr:%#x\n", pf_info.first);
return nullptr;
}
/* Create a prefetch memory request */
RequestPtr pf_req =
std::make_shared<Request>(pf_info.first, blkSize, 0, masterId);
if (is_secure) {
pf_req->setFlags(Request::SECURE);
}
pf_req->taskId(ContextSwitchTaskId::Prefetcher);
PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
pf_pkt->allocate();
/* Verify prefetch buffer space for request */
if (pfq.size() == queueSize) {
pfRemovedFull++;
/* Lowest priority packet */
iterator it = pfq.end();
panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!");
--it;
/* Look for oldest in that level of priority */
panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!");
iterator prev = it;
bool cont = true;
/* While not at the head of the queue */
while (cont && prev != pfq.begin()) {
prev--;
/* While at the same level of priority */
cont = (*prev).priority == (*it).priority;
if (cont)
/* update pointer */
it = prev;
}
DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority "
"oldest packet, addr: %#x", it->pkt->getAddr());
delete it->pkt;
pfq.erase(it);
}
Tick pf_time = curTick() + clockPeriod() * latency;
DPRINTF(HWPrefetch, "Prefetch queued. "
"addr:%#x priority: %3d tick:%lld.\n",
pf_info.first, pf_info.second, pf_time);
/* Create the packet and find the spot to insert it */
DeferredPacket dpp(pf_time, pf_pkt, pf_info.second);
if (pfq.size() == 0) {
pfq.emplace_back(dpp);
} else {
iterator it = pfq.end();
do {
--it;
} while (it != pfq.begin() && dpp > *it);
/* If we reach the head, we have to see if the new element is new head
* or not */
if (it == pfq.begin() && dpp <= *it)
it++;
pfq.insert(it, dpp);
}
return pf_pkt;
}