Nikos Nikoleris has submitted this change and it was merged. (
https://gem5-review.googlesource.com/10422 )
Change subject: mem-cache: Determine if an MSHR has requests from another
cache
......................................................................
mem-cache: Determine if an MSHR has requests from another cache
To decide whether we allocate upon receiving a response we need to
determine if any of the currently serviced requests (non-deferred
targets) is comming from another cache. This change adds support for
tracking this information in the MSHR.
Change-Id: If1db93c12b6af5813b91b9d6b6e5e196d327f038
Reviewed-on: https://gem5-review.googlesource.com/10422
Reviewed-by: Jason Lowe-Power <ja...@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikole...@arm.com>
---
M src/mem/cache/cache.cc
M src/mem/cache/mshr.cc
M src/mem/cache/mshr.hh
3 files changed, 33 insertions(+), 11 deletions(-)
Approvals:
Jason Lowe-Power: Looks good to me, approved
Nikos Nikoleris: Looks good to me, approved
diff --git a/src/mem/cache/cache.cc b/src/mem/cache/cache.cc
index 73c7e19..e9aec49 100644
--- a/src/mem/cache/cache.cc
+++ b/src/mem/cache/cache.cc
@@ -1415,7 +1415,6 @@
// First offset for critical word first calculations
int initial_offset = initial_tgt->pkt->getOffset(blkSize);
- bool from_cache = false;
MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
for (auto &target: targets) {
Packet *tgt_pkt = target.pkt;
@@ -1437,10 +1436,6 @@
break; // skip response
}
- // keep track of whether we have responded to another
- // cache
- from_cache = from_cache || tgt_pkt->fromCache();
-
// unlike the other packet flows, where data is found in other
// caches or memory and brought back, write-line requests
always
// have the data right away, so the above check for "is fill?"
@@ -1572,7 +1567,7 @@
}
}
- maintainClusivity(from_cache, blk);
+ maintainClusivity(targets.hasFromCache, blk);
if (blk && blk->isValid()) {
// an invalidate response stemming from a write line request
diff --git a/src/mem/cache/mshr.cc b/src/mem/cache/mshr.cc
index cc26b56..4f170e6 100644
--- a/src/mem/cache/mshr.cc
+++ b/src/mem/cache/mshr.cc
@@ -68,7 +68,8 @@
}
MSHR::TargetList::TargetList()
- : needsWritable(false), hasUpgrade(false), allocOnFill(false)
+ : needsWritable(false), hasUpgrade(false), allocOnFill(false),
+ hasFromCache(false)
{}
@@ -91,6 +92,10 @@
// potentially re-evaluate whether we should allocate on a fill or
// not
allocOnFill = allocOnFill || alloc_on_fill;
+
+ if (source != Target::FromPrefetcher) {
+ hasFromCache = hasFromCache || pkt->fromCache();
+ }
}
}
@@ -590,7 +595,7 @@
void
MSHR::print(std::ostream &os, int verbosity, const std::string &prefix)
const
{
- ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n",
+ ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s %s\n",
prefix, blkAddr, blkAddr + blkSize - 1,
isSecure ? "s" : "ns",
isForward ? "Forward" : "",
@@ -600,7 +605,8 @@
inService ? "InSvc" : "",
downstreamPending ? "DwnPend" : "",
postInvalidate ? "PostInv" : "",
- postDowngrade ? "PostDowngr" : "");
+ postDowngrade ? "PostDowngr" : "",
+ hasFromCache() ? "HasFromCache" : "");
if (!targets.empty()) {
ccprintf(os, "%s Targets:\n", prefix);
diff --git a/src/mem/cache/mshr.hh b/src/mem/cache/mshr.hh
index 5fe0fb9..b4bf33a 100644
--- a/src/mem/cache/mshr.hh
+++ b/src/mem/cache/mshr.hh
@@ -162,6 +162,11 @@
bool hasUpgrade;
/** Set when the response should allocate on fill */
bool allocOnFill;
+ /**
+ * Determine whether there was at least one non-snooping
+ * target coming from another cache.
+ */
+ bool hasFromCache;
TargetList();
@@ -176,7 +181,12 @@
void updateFlags(PacketPtr pkt, Target::Source source,
bool alloc_on_fill);
- void resetFlags() { needsWritable = hasUpgrade = allocOnFill =
false; }
+ void resetFlags() {
+ needsWritable = false;
+ hasUpgrade = false;
+ allocOnFill = false;
+ hasFromCache = false;
+ }
/**
* Goes through the list of targets and uses them to populate
@@ -191,7 +201,8 @@
* values.
*/
bool isReset() const {
- return !needsWritable && !hasUpgrade && !allocOnFill;
+ return !needsWritable && !hasUpgrade && !allocOnFill &&
+ !hasFromCache;
}
/**
@@ -257,6 +268,16 @@
bool allocOnFill() const {
return targets.allocOnFill;
}
+
+ /**
+ * Determine if there are non-deferred requests from other caches
+ *
+ * @return true if any of the targets is from another cache
+ */
+ bool hasFromCache() const {
+ return targets.hasFromCache;
+ }
+
private:
/**
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: If1db93c12b6af5813b91b9d6b6e5e196d327f038
Gerrit-Change-Number: 10422
Gerrit-PatchSet: 5
Gerrit-Owner: Nikos Nikoleris <nikos.nikole...@arm.com>
Gerrit-Reviewer: Daniel Carvalho <oda...@yahoo.com.br>
Gerrit-Reviewer: Jason Lowe-Power <ja...@lowepower.com>
Gerrit-Reviewer: Nikos Nikoleris <nikos.nikole...@arm.com>
Gerrit-MessageType: merged
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