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mem-cache: Use CircularQueue in PIF prefetcher

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Use CircularQueue for PIF's history buffer, and change the indexing
storage to a CQ iterator.

Change-Id: I75bbb75a6be41bd063f662baedbd4c9de33644de
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24540
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.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 18:43:47 +01:00
committed by Daniel Carvalho
parent 2d5ae09fb3
commit feb2042cb1
2 changed files with 13 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
src/mem/cache/prefetch/pif.cc vendored
View File

@@ -41,12 +41,11 @@ PIF::PIF(const PIFPrefetcherParams *p)
precSize(p->prec_spatial_region_bits),
succSize(p->succ_spatial_region_bits),
maxCompactorEntries(p->compactor_entries),
maxStreamAddressBufferEntries(p->stream_address_buffer_entries),
historyBuffer(p->history_buffer_size),
historyBufferTail(0),
index(p->index_assoc, p->index_entries, p->index_indexing_policy,
p->index_replacement_policy),
streamAddressBuffer(), listenersPC()
streamAddressBuffer(p->stream_address_buffer_entries),
listenersPC()
{
}
@@ -169,8 +168,8 @@ PIF::notifyRetiredInst(const Addr pc)
// updating the trigger address and resetting the vector bits
if (!is_in_temporal_compactor) {
// Insert the spatial entry into the history buffer and update
// the 'index' table to point to the new entry
historyBuffer[historyBufferTail] = spatialCompactor;
// the 'iterator' table to point to the new entry
historyBuffer.push_back(spatialCompactor);
IndexEntry *idx_entry =
index.findEntry(spatialCompactor.trigger, false);
@@ -182,12 +181,8 @@ PIF::notifyRetiredInst(const Addr pc)
index.insertEntry(spatialCompactor.trigger, false,
idx_entry);
}
idx_entry->historyIndex = historyBufferTail;
historyBufferTail++;
if (historyBufferTail == historyBuffer.size()) {
historyBufferTail = 0;
}
idx_entry->historyIt =
historyBuffer.getIterator(historyBuffer.tail());
// Reset the spatial compactor fields with the new address
spatialCompactor = CompactorEntry(pc, precSize, succSize);
@@ -206,13 +201,7 @@ PIF::calculatePrefetch(const PrefetchInfo &pfi,
// comparing the access against the active Stream Address Buffers
for (auto &sabEntry : streamAddressBuffer) {
if (sabEntry->hasAddress(addr, lBlkSize)) {
// Advance to the next entry (first check if we have reached the
// end of the history buffer)
if (sabEntry == &(historyBuffer[historyBuffer.size() - 1])) {
sabEntry = &(historyBuffer[0]);
} else {
sabEntry++;
}
sabEntry++;
sabEntry->getPredictedAddresses(lBlkSize, addresses);
// We are done
return;
@@ -227,13 +216,9 @@ PIF::calculatePrefetch(const PrefetchInfo &pfi,
index.accessEntry(idx_entry);
// Trigger address from the 'index' table and index to the history
// buffer
const unsigned int hb_entry = idx_entry->historyIndex;
CompactorEntry *entry = &historyBuffer[hb_entry];
auto entry = idx_entry->historyIt;
// Track the block in the Stream Address Buffer
if (streamAddressBuffer.size() == maxStreamAddressBufferEntries) {
streamAddressBuffer.pop_front();
}
streamAddressBuffer.push_back(entry);
entry->getPredictedAddresses(lBlkSize, addresses);

11
src/mem/cache/prefetch/pif.hh vendored
View File

@@ -40,6 +40,7 @@
#include <deque>
#include <vector>
#include "base/circular_queue.hh"
#include "mem/cache/prefetch/associative_set.hh"
#include "mem/cache/prefetch/queued.hh"
@@ -55,8 +56,6 @@ class PIF : public Queued
const unsigned int succSize;
/** Number of entries used for the temporal compactor */
const unsigned int maxCompactorEntries;
/** Max number of entries to be used in the Stream Address Buffer */
const unsigned int maxStreamAddressBufferEntries;
/**
* The compactor tracks retired instructions addresses, leveraging the
@@ -127,12 +126,12 @@ class PIF : public Queued
* History buffer is a circular buffer that stores the sequence of
* retired instructions in FIFO order.
*/
std::vector<CompactorEntry> historyBuffer;
unsigned int historyBufferTail;
using HistoryBuffer = CircularQueue<CompactorEntry>;
HistoryBuffer historyBuffer;
struct IndexEntry : public TaggedEntry
{
unsigned int historyIndex;
HistoryBuffer::iterator historyIt;
};
/**
* The index table is a small cache-like structure that facilitates
@@ -146,7 +145,7 @@ class PIF : public Queued
* history buffer, initiallly set to the pointer taken from the index
* table
*/
std::deque<CompactorEntry*> streamAddressBuffer;
CircularQueue<HistoryBuffer::iterator> streamAddressBuffer;
/**
* Updates the prefetcher structures upon an instruction retired