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mem: Avoid adding and then removing empty snoop-filter items

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This patch tidies up how we access the snoop filter for snoops, and
avoids adding items only to later remove them.
This commit is contained in:
Andreas Hansson 2015-09-25 07:26:57 -04:00
parent ca163a80e2
commit 7d4e89d4e0
1 changed files with 26 additions and 30 deletions
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56
src/mem/snoop_filter.cc
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@ -174,12 +174,6 @@ SnoopFilter::lookupSnoop(const Packet* cpkt)
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 @@ SnoopFilter::lookupSnoop(const Packet* cpkt)
"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 @@ SnoopFilter::lookupSnoop(const Packet* cpkt)
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 @@ SnoopFilter::updateSnoopForward(const Packet* cpkt,
__func__, rsp_port.name(), req_port.name(), cpkt->getAddr(),
cpkt->cmdString());
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;
SnoopItem& sf_item = sf_it->second;
SnoopMask rsp_mask M5_VAR_USED = portToMask(rsp_port);
assert(cpkt->isResponse());
assert(cpkt->memInhibitAsserted());
Addr line_addr = cpkt->getBlockAddr(linesize);
auto sf_it = cachedLocations.find(line_addr);
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;
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 @@ SnoopFilter::updateSnoopForward(const Packet* cpkt,
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
__func__, sf_item.requested, sf_item.holder);
eraseIfNullEntry(sf_it);
}
void