mem-cache: Make StridePrefetcher use Replacement Policies
Previously StridePrefetcher was only able to use random
replacement policy. This change allows all replacement
policies to be applied to the pc table.
Change-Id: I8714e71a6a4c9c31fbca49a07a456dcacd3e402c
Signed-off-by: Daniel <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/14360
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
diff --git a/src/mem/cache/prefetch/Prefetcher.py b/src/mem/cache/prefetch/Prefetcher.py
index 09717df..bae235d 100644
--- a/src/mem/cache/prefetch/Prefetcher.py
+++ b/src/mem/cache/prefetch/Prefetcher.py
@@ -43,6 +43,7 @@
from m5.SimObject import *
from m5.params import *
from m5.proxy import *
+from ReplacementPolicies import *
class HWPProbeEvent(object):
def __init__(self, prefetcher, obj, *listOfNames):
@@ -126,6 +127,10 @@
degree = Param.Int(4, "Number of prefetches to generate")
+ # Get replacement policy
+ replacement_policy = Param.BaseReplacementPolicy(RandomRP(),
+ "Replacement policy")
+
class TaggedPrefetcher(QueuedPrefetcher):
type = 'TaggedPrefetcher'
cxx_class = 'TaggedPrefetcher'
diff --git a/src/mem/cache/prefetch/stride.cc b/src/mem/cache/prefetch/stride.cc
index 4520f12..44849cd 100644
--- a/src/mem/cache/prefetch/stride.cc
+++ b/src/mem/cache/prefetch/stride.cc
@@ -1,4 +1,5 @@
/*
+ * Copyright (c) 2018 Inria
* Copyright (c) 2012-2013, 2015 ARM Limited
* All rights reserved
*
@@ -39,6 +40,7 @@
*
* Authors: Ron Dreslinski
* Steve Reinhardt
+ * Daniel Carvalho
*/
/**
@@ -55,6 +57,7 @@
#include "base/random.hh"
#include "base/trace.hh"
#include "debug/HWPrefetch.hh"
+#include "mem/cache/replacement_policies/base.hh"
#include "params/StridePrefetcher.hh"
StridePrefetcher::StrideEntry::StrideEntry()
@@ -81,7 +84,8 @@
pcTableAssoc(p->table_assoc),
pcTableSets(p->table_sets),
useMasterId(p->use_master_id),
- degree(p->degree)
+ degree(p->degree),
+ replacementPolicy(p->replacement_policy)
{
assert(isPowerOf2(pcTableSets));
}
@@ -103,7 +107,7 @@
{
// Create new table
auto insertion_result = pcTables.insert(std::make_pair(context,
- PCTable(pcTableAssoc, pcTableSets, name())));
+ PCTable(pcTableAssoc, pcTableSets, name(), replacementPolicy)));
DPRINTF(HWPrefetch, "Adding context %i with stride entries\n", context);
@@ -111,11 +115,21 @@
return &(insertion_result.first->second);
}
-StridePrefetcher::PCTable::PCTable(int assoc, int sets, const std::string name)
- : pcTableAssoc(assoc), pcTableSets(sets), _name(name), entries(pcTableSets)
+StridePrefetcher::PCTable::PCTable(int assoc, int sets, const std::string name,
+ BaseReplacementPolicy* replacementPolicy)
+ : pcTableSets(sets), _name(name), entries(pcTableSets),
+ replacementPolicy(replacementPolicy)
{
- for (auto& set : entries) {
- set.resize(pcTableAssoc);
+ for (int set = 0; set < sets; set++) {
+ entries[set].resize(assoc);
+ for (int way = 0; way < assoc; way++) {
+ // Inform the entry its position
+ entries[set][way].setPosition(set, way);
+
+ // Initialize replacement policy data
+ entries[set][way].replacementData =
+ replacementPolicy->instantiateEntry();
+ }
}
}
@@ -200,12 +214,14 @@
// Invalidate victim
entry->invalidate();
+ replacementPolicy->invalidate(entry->replacementData);
// Insert new entry's data
entry->instAddr = pc;
entry->lastAddr = pkt_addr;
- entry->isSecure= is_secure;
+ entry->isSecure = is_secure;
entry->confidence = startConf;
+ replacementPolicy->reset(entry->replacementData);
}
}
@@ -222,23 +238,34 @@
{
// 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 &entries[set][way];
+ // Get possible entries to be victimized
+ std::vector<ReplaceableEntry*> possible_entries;
+ for (auto& entry : entries[set]) {
+ possible_entries.push_back(&entry);
+ }
+
+ // Choose victim based on replacement policy
+ StrideEntry* victim = static_cast<StrideEntry*>(
+ replacementPolicy->getVictim(possible_entries));
+
+ DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n",
+ victim->getSet(), victim->getWay());
+
+ return victim;
}
inline StridePrefetcher::StrideEntry*
StridePrefetcher::PCTable::findEntry(Addr pc, bool is_secure)
{
int set = pcHash(pc);
- std::vector<StrideEntry>& set_entries = entries[set];
- for (int way = 0; way < pcTableAssoc; way++) {
- StrideEntry* entry = &set_entries[way];
+ for (auto& entry : entries[set]) {
// Search ways for match
- if ((entry->instAddr == pc) && (entry->isSecure == is_secure)) {
- DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way);
- return entry;
+ if ((entry.instAddr == pc) && (entry.isSecure == is_secure)) {
+ DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", entry.getSet(),
+ entry.getWay());
+ replacementPolicy->touch(entry.replacementData);
+ return &entry;
}
}
return nullptr;
diff --git a/src/mem/cache/prefetch/stride.hh b/src/mem/cache/prefetch/stride.hh
index 772c3a5..aa02287 100644
--- a/src/mem/cache/prefetch/stride.hh
+++ b/src/mem/cache/prefetch/stride.hh
@@ -1,4 +1,5 @@
/*
+ * Copyright (c) 2018 Inria
* Copyright (c) 2012-2013, 2015 ARM Limited
* All rights reserved
*
@@ -38,6 +39,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Ron Dreslinski
+ * Daniel Carvalho
*/
/**
@@ -54,8 +56,10 @@
#include "base/types.hh"
#include "mem/cache/prefetch/queued.hh"
+#include "mem/cache/replacement_policies/replaceable_entry.hh"
#include "mem/packet.hh"
+class BaseReplacementPolicy;
struct StridePrefetcherParams;
class StridePrefetcher : public QueuedPrefetcher
@@ -73,7 +77,10 @@
const int degree;
- struct StrideEntry
+ /** Replacement policy used in the PC tables. */
+ BaseReplacementPolicy* replacementPolicy;
+
+ struct StrideEntry : public ReplaceableEntry
{
/** Default constructor */
StrideEntry();
@@ -97,8 +104,10 @@
* @param assoc Associativity of the table.
* @param sets Number of sets in the table.
* @param name Name of the prefetcher.
+ * @param replacementPolicy Replacement policy used by the table.
*/
- PCTable(int assoc, int sets, const std::string name);
+ PCTable(int assoc, int sets, const std::string name,
+ BaseReplacementPolicy* replacementPolicy);
/**
* Default destructor.
@@ -124,12 +133,16 @@
private:
const std::string name() {return _name; }
- const int pcTableAssoc;
const int pcTableSets;
const std::string _name;
std::vector<std::vector<StrideEntry>> entries;
/**
+ * Replacement policy used by StridePrefetcher.
+ */
+ BaseReplacementPolicy* replacementPolicy;
+
+ /**
* PC hashing function to index sets in the table.
*
* @param pc The PC value.
