From 6279eaf1f7d28b370ede16d52475a7da372d2dde Mon Sep 17 00:00:00 2001
From: Andreas Hansson <andreas.hansson@arm.com>
Date: Mon, 19 Aug 2013 03:52:32 -0400
Subject: [PATCH] mem: Use STL deque in favour of list for DRAM queues

This patch changes the data structure used for the DRAM read, write
and response queues from an STL list to deque. This optimisation is
based on the observation that the size is small (and fixed), and that
the structures are frequently iterated over in a linear fashion.
---
 src/mem/simple_dram.cc | 19 +++++++------------
 src/mem/simple_dram.hh |  6 +++---
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/src/mem/simple_dram.cc b/src/mem/simple_dram.cc
index e8c1dfbcd..033ccbb26 100644
--- a/src/mem/simple_dram.cc
+++ b/src/mem/simple_dram.cc
@@ -310,8 +310,7 @@ SimpleDRAM::addToReadQueue(PacketPtr pkt, unsigned int pktCount)
         // First check write buffer to see if the data is already at
         // the controller
         bool foundInWrQ = false;
-        list<DRAMPacket*>::const_iterator i;
-        for (i = writeQueue.begin(); i != writeQueue.end(); ++i) {
+        for (auto i = writeQueue.begin(); i != writeQueue.end(); ++i) {
             // check if the read is subsumed in the write entry we are
             // looking at
             if ((*i)->addr <= addr &&
@@ -662,19 +661,16 @@ SimpleDRAM::printParams() const
 
 void
 SimpleDRAM::printQs() const {
-
-    list<DRAMPacket*>::const_iterator i;
-
     DPRINTF(DRAM, "===READ QUEUE===\n\n");
-    for (i = readQueue.begin() ;  i != readQueue.end() ; ++i) {
+    for (auto i = readQueue.begin() ;  i != readQueue.end() ; ++i) {
         DPRINTF(DRAM, "Read %lu\n", (*i)->addr);
     }
     DPRINTF(DRAM, "\n===RESP QUEUE===\n\n");
-    for (i = respQueue.begin() ;  i != respQueue.end() ; ++i) {
+    for (auto i = respQueue.begin() ;  i != respQueue.end() ; ++i) {
         DPRINTF(DRAM, "Response %lu\n", (*i)->addr);
     }
     DPRINTF(DRAM, "\n===WRITE QUEUE===\n\n");
-    for (i = writeQueue.begin() ;  i != writeQueue.end() ; ++i) {
+    for (auto i = writeQueue.begin() ;  i != writeQueue.end() ; ++i) {
         DPRINTF(DRAM, "Write %lu\n", (*i)->addr);
     }
 }
@@ -829,7 +825,7 @@ SimpleDRAM::chooseNextWrite()
     if (memSchedPolicy == Enums::fcfs) {
         // Do nothing, since the correct request is already head
     } else if (memSchedPolicy == Enums::frfcfs) {
-        list<DRAMPacket*>::iterator i = writeQueue.begin();
+        auto i = writeQueue.begin();
         bool foundRowHit = false;
         while (!foundRowHit && i != writeQueue.end()) {
             DRAMPacket* dram_pkt = *i;
@@ -870,8 +866,7 @@ SimpleDRAM::chooseNextRead()
         // Do nothing, since the request to serve is already the first
         // one in the read queue
     } else if (memSchedPolicy == Enums::frfcfs) {
-        for (list<DRAMPacket*>::iterator i = readQueue.begin();
-             i != readQueue.end() ; ++i) {
+        for (auto i = readQueue.begin(); i != readQueue.end() ; ++i) {
             DRAMPacket* dram_pkt = *i;
             const Bank& bank = dram_pkt->bank_ref;
             // Check if it is a row hit
@@ -1153,7 +1148,7 @@ SimpleDRAM::moveToRespQ()
         schedule(respondEvent, dram_pkt->readyTime);
     } else {
         bool done = false;
-        list<DRAMPacket*>::iterator i = respQueue.begin();
+        auto i = respQueue.begin();
         while (!done && i != respQueue.end()) {
             if ((*i)->readyTime > dram_pkt->readyTime) {
                 respQueue.insert(i, dram_pkt);
diff --git a/src/mem/simple_dram.hh b/src/mem/simple_dram.hh
index 9473f010f..abc64c3cd 100644
--- a/src/mem/simple_dram.hh
+++ b/src/mem/simple_dram.hh
@@ -406,8 +406,8 @@ class SimpleDRAM : public AbstractMemory
     /**
      * The controller's main read and write queues
      */
-    std::list<DRAMPacket*> readQueue;
-    std::list<DRAMPacket*> writeQueue;
+    std::deque<DRAMPacket*> readQueue;
+    std::deque<DRAMPacket*> writeQueue;
 
     /**
      * Response queue where read packets wait after we're done working
@@ -417,7 +417,7 @@ class SimpleDRAM : public AbstractMemory
      * as sizing the read queue, this and the main read queue need to
      * be added together.
      */
-    std::list<DRAMPacket*> respQueue;
+    std::deque<DRAMPacket*> respQueue;
 
     /**
      * If we need to drain, keep the drain manager around until we're
-- 
2.30.2