changeset dfa51840de1f in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=dfa51840de1f
description:
mem: Avoid adding and then removing empty snoop-filter items
This patch tidies up how we access the snoop filter for snoops, and
avoids adding items only to later remove them.
diffstat:
src/mem/snoop_filter.cc | 54 ++++++++++++++++++++++--------------------------
1 files changed, 25 insertions(+), 29 deletions(-)
diffs (102 lines):
diff -r 81e46b63daff -r dfa51840de1f src/mem/snoop_filter.cc
--- a/src/mem/snoop_filter.cc Fri Sep 25 07:26:57 2015 -0400
+++ b/src/mem/snoop_filter.cc Fri Sep 25 07:26:57 2015 -0400
@@ -174,12 +174,6 @@
assert(cpkt->isRequest());
- // Broadcast / filter upward snoops
- const bool filter_upward = true; // @todo: Make configurable
-
- if (!filter_upward)
- return snoopAll(lookupLatency);
-
Addr line_addr = cpkt->getBlockAddr(linesize);
auto sf_it = cachedLocations.find(line_addr);
bool is_hit = (sf_it != cachedLocations.end());
@@ -188,15 +182,12 @@
"snoop filter exceeded capacity of %d cache blocks\n",
maxEntryCount);
- // If the snoop filter has no entry and its an uncacheable
- // request, do not create a new snoop filter entry, simply return
- // a NULL portlist.
- if (!is_hit && cpkt->req->isUncacheable())
+ // If the snoop filter has no entry, simply return a NULL
+ // portlist, there is no point creating an entry only to remove it
+ // later
+ if (!is_hit)
return snoopDown(lookupLatency);
- // If no hit in snoop filter create a new element and update iterator
- if (!is_hit)
- sf_it = cachedLocations.emplace(line_addr, SnoopItem()).first;
SnoopItem& sf_item = sf_it->second;
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
@@ -205,13 +196,12 @@
SnoopMask interested = (sf_item.holder | sf_item.requested);
totSnoops++;
- if (is_hit) {
- // Single bit set -> value is a power of two
- if (isPow2(interested))
- hitSingleSnoops++;
- else
- hitMultiSnoops++;
- }
+ // Single bit set -> value is a power of two
+ if (isPow2(interested))
+ hitSingleSnoops++;
+ else
+ hitMultiSnoops++;
+
// ReadEx and Writes require both invalidation and exlusivity, while reads
// require neither. Writebacks on the other hand require exclusivity but
// not the invalidation. Previously Writebacks did not generate upward
@@ -296,23 +286,28 @@
__func__, rsp_port.name(), req_port.name(), cpkt->getAddr(),
cpkt->cmdString());
+ assert(cpkt->isResponse());
+ assert(cpkt->memInhibitAsserted());
+
Addr line_addr = cpkt->getBlockAddr(linesize);
auto sf_it = cachedLocations.find(line_addr);
- if (sf_it == cachedLocations.end())
- sf_it = cachedLocations.emplace(line_addr, SnoopItem()).first;
+ bool is_hit = sf_it != cachedLocations.end();
+
+ // Nothing to do if it is not a hit
+ if (!is_hit)
+ return;
+
SnoopItem& sf_item = sf_it->second;
- SnoopMask rsp_mask M5_VAR_USED = portToMask(rsp_port);
-
- assert(cpkt->isResponse());
- assert(cpkt->memInhibitAsserted());
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
__func__, sf_item.requested, sf_item.holder);
- // Remote (to this snoop filter) snoops update the filter already when they
- // arrive from below, because we may not see any response.
+ // Remote (to this snoop filter) snoops update the filter
+ // already when they arrive from below, because we may not see
+ // any response.
if (cpkt->needsExclusive()) {
- // If the request to this snoop response hit an in-flight transaction,
+ // If the request to this snoop response hit an in-flight
+ // transaction,
// the holder was not reset -> no assertion & do that here, now!
//assert(sf_item.holder == 0);
sf_item.holder = 0;
@@ -320,6 +315,7 @@
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
__func__, sf_item.requested, sf_item.holder);
eraseIfNullEntry(sf_it);
+
}
void
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