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mem-cache: Use CircularQueue for the STeMS's RMOB

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Replace rmobHead functionality with a CircularQueue. As a side
effect, RMOB entry's valid bit was removed.

Change-Id: If0b39cfe15de1e47dde0689a0ebc46b623ec1e55
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24539
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Javier Bueno Hedo <javier.bueno@metempsy.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Daniel R. Carvalho
2019-12-29 16:20:04 +01:00
committed by Daniel Carvalho
parent 01a8783d58
commit 2d5ae09fb3
2 changed files with 33 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
src/mem/cache/prefetch/spatio_temporal_memory_streaming.cc vendored
View File

@@ -50,7 +50,7 @@ STeMS::STeMS(const STeMSPrefetcherParams *p)
p->pattern_sequence_table_replacement_policy,
ActiveGenerationTableEntry(
spatialRegionSize / blkSize)),
rmob(p->region_miss_order_buffer_entries), rmobHead(0)
rmob(p->region_miss_order_buffer_entries)
{
fatal_if(!isPowerOf2(spatialRegionSize),
"The spatial region size must be a power of 2.");
@@ -106,13 +106,12 @@ STeMS::checkForActiveGenerationsEnd()
void
STeMS::addToRMOB(Addr sr_addr, Addr pst_addr, unsigned int delta)
{
RegionMissOrderBufferEntry &rmob_entry = rmob[rmobHead];
rmobHead = (rmobHead + 1) % rmob.size();
RegionMissOrderBufferEntry rmob_entry;
rmob_entry.srAddress = sr_addr;
rmob_entry.pstAddress = pst_addr;
rmob_entry.delta = delta;
rmob_entry.valid = true;
rmob.push_back(rmob_entry);
}
void
@@ -171,13 +170,12 @@ STeMS::calculatePrefetch(const PrefetchInfo &pfi,
// Prefetch generation: if this is a miss, search for the most recent
// entry in the RMOB, and reconstruct the registered access sequence
if (pfi.isCacheMiss()) {
for (unsigned int idx = (rmobHead - 1) % rmob.size();
idx != rmobHead && rmob[idx].valid;
idx = (idx - 1) % rmob.size())
{
if (rmob[idx].srAddress == sr_addr) {
auto it = rmob.end();
while (it != rmob.begin()) {
--it;
if (it->srAddress == sr_addr) {
// reconstruct the access sequence
reconstructSequence(idx, addresses);
reconstructSequence(it, addresses);
break;
}
}
@@ -185,37 +183,34 @@ STeMS::calculatePrefetch(const PrefetchInfo &pfi,
}
void
STeMS::reconstructSequence(unsigned int rmob_idx,
STeMS::reconstructSequence(
CircularQueue<RegionMissOrderBufferEntry>::iterator rmob_it,
std::vector<AddrPriority> &addresses)
{
std::vector<Addr> reconstruction(reconstructionEntries, MaxAddr);
unsigned int idx = 0;
// process rmob entries from rmob_idx (most recent with
// address = sr_addr) to the last one (rmobHead)
for (int i = rmob_idx;
i != rmobHead && idx < reconstructionEntries;
i = (i + 1) % rmob.size())
{
reconstruction[idx] = rmob[i].srAddress * spatialRegionSize;
unsigned int next_i = (i + 1) % rmob.size();
idx += rmob[next_i].delta + 1;
// Process rmob entries from rmob_it (most recent with address = sr_addr)
// to the latest one
for (auto it = rmob_it; it != rmob.end() && (idx < reconstructionEntries);
it++) {
reconstruction[idx] = it->srAddress * spatialRegionSize;
idx += (it+1)->delta + 1;
}
// Now query the PST with the PC of each RMOB entry
idx = 0;
for (int i = rmob_idx;
i != rmobHead && idx < reconstructionEntries;
i = (i + 1) % rmob.size())
{
for (auto it = rmob_it; it != rmob.end() && (idx < reconstructionEntries);
it++) {
ActiveGenerationTableEntry *pst_entry =
patternSequenceTable.findEntry(rmob[i].pstAddress,
false /* unused */);
patternSequenceTable.findEntry(it->pstAddress, false /* unused */);
if (pst_entry != nullptr) {
patternSequenceTable.accessEntry(pst_entry);
for (auto &seq_entry : pst_entry->sequence) {
if (seq_entry.counter > 1) {
// 2-bit counter: high enough confidence with a
// value greater than 1
Addr rec_addr = rmob[i].srAddress * spatialRegionSize +
Addr rec_addr = it->srAddress * spatialRegionSize +
seq_entry.offset;
unsigned ridx = idx + seq_entry.delta;
// Try to use the corresponding position, if it has been
@@ -241,9 +236,9 @@ STeMS::reconstructSequence(unsigned int rmob_idx,
}
}
}
unsigned int next_i = (i + 1) % rmob.size();
idx += rmob[next_i].delta + 1;
idx += (it+1)->delta + 1;
}
for (Addr pf_addr : reconstruction) {
if (pf_addr != MaxAddr) {
addresses.push_back(AddrPriority(pf_addr, 0));

16
src/mem/cache/prefetch/spatio_temporal_memory_streaming.hh vendored
View File

@@ -43,6 +43,7 @@
#include <vector>
#include "base/circular_queue.hh"
#include "base/sat_counter.hh"
#include "mem/cache/prefetch/associative_set.hh"
#include "mem/cache/prefetch/queued.hh"
@@ -161,14 +162,10 @@ class STeMS : public Queued
Addr pstAddress;
/** Delta within the global miss order sequence */
unsigned int delta;
/** Valid bit */
bool valid;
};
/** Region Miss Order Buffer (RMOB) */
std::vector<RegionMissOrderBufferEntry> rmob;
/** First free position (or older, if it is full) of the RMOB */
unsigned int rmobHead;
CircularQueue<RegionMissOrderBufferEntry> rmob;
/** Counter to keep the count of accesses between trigger accesses */
unsigned int lastTriggerCounter;
@@ -186,11 +183,14 @@ class STeMS : public Queued
/**
* Reconstructs a sequence of accesses and generates the prefetch
* addresses, adding them to the addresses vector
* @param rmob_idx rmob position to start generating from
*
* @param rmob_it rmob position to start generating from.
* @param addresses vector to add the addresses to be prefetched
*/
void reconstructSequence(unsigned int rmob_idx,
std::vector<AddrPriority> &addresses);
void reconstructSequence(
CircularQueue<RegionMissOrderBufferEntry>::iterator rmob_it,
std::vector<AddrPriority> &addresses);
public:
STeMS(const STeMSPrefetcherParams* p);
~STeMS() = default;