From e2b3f0b8e4e50e40637361fe095ca2cfef914430 Mon Sep 17 00:00:00 2001
From: Yu-hsin Wang <yuhsingw@google.com>
Date: Wed, 6 Dec 2023 13:25:02 +0800
Subject: [PATCH] mem: Add a flag on AbstractMemory to control statistics
 collection

The stats initialization in the AbstractMemory allocates the space
according to the max requestors of the System. This may cause issues in
multiple system simulation.
Given there are two system A and B. A has one requestor and a memory,
while B has two requestors. When the requestor with requestor id 2
sending requests to the meomry in A, the simulator would crash because
requestor id 2 is out of the allocated space.

Current solution is adding a SysBridge between across A and B which
would rewrite the requestor id to a valid one. This solution works but
it needs to the bridge at the correct boundary which may not easy. In
addition, the stats would record a mapped data which may not accurate.

To reduce the complexity, we add an flag to AbstractMemory to control
the stats. If users don't want the statistics and want to solve the
cross system issue simply, users can disable the statistics collection.
We also makes the flag by default True to not disturb current users.

Change-Id: Ibb46a63d216d4f310b3e920815a295073496ea6e
---
 src/mem/AbstractMemory.py |  2 ++
 src/mem/abstract_mem.cc   | 23 ++++++++++++++---------
 src/mem/abstract_mem.hh   |  3 +++
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/mem/AbstractMemory.py b/src/mem/AbstractMemory.py
index 57e47adcb1..32d18adab2 100644
--- a/src/mem/AbstractMemory.py
+++ b/src/mem/AbstractMemory.py
@@ -76,3 +76,5 @@ class AbstractMemory(ClockedObject):
     )
 
     writeable = Param.Bool(True, "Allow writes to this memory")
+
+    collect_stats = Param.Bool(True, "Collect traffic statistics")
diff --git a/src/mem/abstract_mem.cc b/src/mem/abstract_mem.cc
index 9340f7e96f..f22ea35527 100644
--- a/src/mem/abstract_mem.cc
+++ b/src/mem/abstract_mem.cc
@@ -63,8 +63,8 @@ AbstractMemory::AbstractMemory(const Params &p) :
                  MemBackdoor::Readable | MemBackdoor::Writeable :
                  MemBackdoor::Readable)),
     confTableReported(p.conf_table_reported), inAddrMap(p.in_addr_map),
-    kvmMap(p.kvm_map), writeable(p.writeable), _system(NULL),
-    stats(*this)
+    kvmMap(p.kvm_map), writeable(p.writeable), collectStats(p.collect_stats),
+    _system(NULL), stats(*this)
 {
     panic_if(!range.valid() || !range.size(),
              "Memory range %s must be valid with non-zero size.",
@@ -433,7 +433,8 @@ AbstractMemory::access(PacketPtr pkt)
 
             assert(!pkt->req->isInstFetch());
             TRACE_PACKET("Read/Write");
-            stats.numOther[pkt->req->requestorId()]++;
+            if (collectStats)
+                stats.numOther[pkt->req->requestorId()]++;
         }
     } else if (pkt->isRead()) {
         assert(!pkt->isWrite());
@@ -447,10 +448,12 @@ AbstractMemory::access(PacketPtr pkt)
             pkt->setData(host_addr);
         }
         TRACE_PACKET(pkt->req->isInstFetch() ? "IFetch" : "Read");
-        stats.numReads[pkt->req->requestorId()]++;
-        stats.bytesRead[pkt->req->requestorId()] += pkt->getSize();
-        if (pkt->req->isInstFetch())
-            stats.bytesInstRead[pkt->req->requestorId()] += pkt->getSize();
+        if (collectStats) {
+            stats.numReads[pkt->req->requestorId()]++;
+            stats.bytesRead[pkt->req->requestorId()] += pkt->getSize();
+            if (pkt->req->isInstFetch())
+                stats.bytesInstRead[pkt->req->requestorId()] += pkt->getSize();
+        }
     } else if (pkt->isInvalidate() || pkt->isClean()) {
         assert(!pkt->isWrite());
         // in a fastmem system invalidating and/or cleaning packets
@@ -466,8 +469,10 @@ AbstractMemory::access(PacketPtr pkt)
             }
             assert(!pkt->req->isInstFetch());
             TRACE_PACKET("Write");
-            stats.numWrites[pkt->req->requestorId()]++;
-            stats.bytesWritten[pkt->req->requestorId()] += pkt->getSize();
+            if (collectStats) {
+                stats.numWrites[pkt->req->requestorId()]++;
+                stats.bytesWritten[pkt->req->requestorId()] += pkt->getSize();
+            }
         }
     } else {
         panic("Unexpected packet %s", pkt->print());
diff --git a/src/mem/abstract_mem.hh b/src/mem/abstract_mem.hh
index 7f12487421..8c85f4503e 100644
--- a/src/mem/abstract_mem.hh
+++ b/src/mem/abstract_mem.hh
@@ -132,6 +132,9 @@ class AbstractMemory : public ClockedObject
     // Are writes allowed to this memory
     const bool writeable;
 
+    // Should collect traffic statistics
+    const bool collectStats;
+
     std::list<LockedAddr> lockedAddrList;
 
     // helper function for checkLockedAddrs(): we really want to