Nikos Nikoleris has uploaded this change for review. (
https://gem5-review.googlesource.com/11017
Change subject: mem-cache: Promote targets that don't require writable
......................................................................
mem-cache: Promote targets that don't require writable
Until now, all deferred targets of an MSHR would be promoted together
as soon as the targets were serviced. Due to the way we handle cache
clean operations we might need to promote only deferred targets that
don't require writable, leaving some targets as deferred. This change
adds support for this selective promotion.
Change-Id: I502e523dc9adbaf394955cbacea8286ab6a9b6bc
---
M src/mem/cache/mshr.cc
M src/mem/cache/mshr.hh
2 files changed, 65 insertions(+), 16 deletions(-)
diff --git a/src/mem/cache/mshr.cc b/src/mem/cache/mshr.cc
index daa2eff..d973dcc 100644
--- a/src/mem/cache/mshr.cc
+++ b/src/mem/cache/mshr.cc
@@ -547,6 +547,45 @@
return true;
}
+void
+MSHR::promoteIf(const std::function<bool (Target &)>& pred)
+{
+ // if any of the deferred targets were upper-level cache
+ // requests marked downstreamPending, need to clear that
+ assert(!downstreamPending); // not pending here anymore
+
+ auto last_it = std::find_if_not(deferredTargets.begin(),
+ deferredTargets.end(),
+ pred);
+ deferredTargets.clearDownstreamPending(deferredTargets.begin(),
+ last_it);
+ targets.splice(targets.end(), deferredTargets,
+ deferredTargets.begin(), last_it);
+ // We need to update the flags for the target lists after the
+ // modifications
+ deferredTargets.populateFlags();
+}
+
+void
+MSHR::promoteReadable()
+{
+ if (!deferredTargets.empty() && !hasPostInvalidate()) {
+ // We got a non invalidating response, and we have the block
+ // but we have deferred targets which are waiting and they do
+ // not need writable. This can happen if the original request
+ // was for a cache clean operation and we had a copy of the
+ // block. Since we serviced the cache clean operation and we
+ // have the block, there's no need to defer the targets, so
+ // move them up to the regular target list.
+
+ auto pred = [](Target &t) {
+ assert(t.source == Target::FromCPU);
+ return !t.pkt->req->isCacheInvalidate() &&
+ !t.pkt->needsWritable();
+ };
+ promoteIf(pred);
+ }
+}
void
MSHR::promoteWritable()
@@ -562,23 +601,13 @@
// target list.
assert(!targets.needsWritable);
targets.needsWritable = true;
- // if any of the deferred targets were upper-level cache
- // requests marked downstreamPending, need to clear that
- assert(!downstreamPending); // not pending here anymore
- auto last_it = std::find_if(
- deferredTargets.begin(), deferredTargets.end(),
- [](MSHR::Target &t) {
- assert(t.source == Target::FromCPU);
- return t.pkt->req->isCacheInvalidate();
- });
- deferredTargets.clearDownstreamPending(deferredTargets.begin(),
- last_it);
- targets.splice(targets.end(), deferredTargets,
- deferredTargets.begin(), last_it);
- // We need to update the flags for the target lists after the
- // modifications
- deferredTargets.populateFlags();
+ auto pred = [](Target &t) {
+ assert(t.source == Target::FromCPU);
+ return !t.pkt->req->isCacheInvalidate();
+ };
+
+ promoteIf(pred);
}
}
diff --git a/src/mem/cache/mshr.hh b/src/mem/cache/mshr.hh
index 71c2da2..d78cb9e 100644
--- a/src/mem/cache/mshr.hh
+++ b/src/mem/cache/mshr.hh
@@ -386,6 +386,26 @@
bool promoteDeferredTargets();
/**
+ * Promotes deferred targets that satisfy a predicate
+ *
+ * Deferred targets are promoted to the target if the satisfy a
+ * give condition. The operation stop at the first deferred target
+ * that doesn't satisfy the condition.
+ *
+ * @param pred A condition on a Target
+ */
+ void promoteIf(const std::function<bool (Target &)>& pred);
+
+ /**
+ * Promotes deferred targets that do not require writable
+ *
+ * Requests in the deferred target list are moved to the target
+ * list up until the first target that is a cache maintenance
+ * operation or needs a writable copy of the block
+ */
+ void promoteReadable();
+
+ /**
* Promotes deferred targets that do not require writable
*
* Requests in the deferred target list are moved to the target
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: I502e523dc9adbaf394955cbacea8286ab6a9b6bc
Gerrit-Change-Number: 11017
Gerrit-PatchSet: 1
Gerrit-Owner: Nikos Nikoleris <[email protected]>
Gerrit-MessageType: newchange
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