From 0c5a98f9d18c6fdae287b1b608d1ffb1c13fb9c9 Mon Sep 17 00:00:00 2001 From: Andreas Hansson Date: Fri, 25 Sep 2015 07:26:57 -0400 Subject: mem: Store snoop filter lookup result to avoid second lookup This patch introduces a private member storing the iterator from the lookupRequest call, such that it can be re-used when the request eventually finishes. The method previously called updateRequest is renamed finishRequest to make it more clear that the two functions must be called together. --- src/mem/snoop_filter.cc | 48 +++++++++++++++++++++--------------------------- 1 file changed, 21 insertions(+), 27 deletions(-) (limited to 'src/mem/snoop_filter.cc') diff --git a/src/mem/snoop_filter.cc b/src/mem/snoop_filter.cc index a52d86380..f6e6ef1b4 100755 --- a/src/mem/snoop_filter.cc +++ b/src/mem/snoop_filter.cc @@ -70,8 +70,8 @@ SnoopFilter::lookupRequest(const Packet* cpkt, const SlavePort& slave_port) bool allocate = !cpkt->req->isUncacheable() && slave_port.isSnooping(); Addr line_addr = cpkt->getBlockAddr(linesize); SnoopMask req_port = portToMask(slave_port); - auto sf_it = cachedLocations.find(line_addr); - bool is_hit = (sf_it != cachedLocations.end()); + reqLookupResult = cachedLocations.find(line_addr); + bool is_hit = (reqLookupResult != cachedLocations.end()); // If the snoop filter has no entry, and we should not allocate, // do not create a new snoop filter entry, simply return a NULL @@ -79,8 +79,10 @@ SnoopFilter::lookupRequest(const Packet* cpkt, const SlavePort& slave_port) if (!is_hit && !allocate) return snoopDown(lookupLatency); - // Create a new element through operator[] and modify in-place - SnoopItem& sf_item = is_hit ? sf_it->second : cachedLocations[line_addr]; + // If no hit in snoop filter create a new element and update iterator + if (!is_hit) + reqLookupResult = cachedLocations.emplace(line_addr, SnoopItem()).first; + SnoopItem& sf_item = reqLookupResult->second; SnoopMask interested = sf_item.holder | sf_item.requested; // Store unmodified value of snoop filter item in temp storage in @@ -144,32 +146,24 @@ SnoopFilter::lookupRequest(const Packet* cpkt, const SlavePort& slave_port) } void -SnoopFilter::updateRequest(const Packet* cpkt, const SlavePort& slave_port, - bool will_retry) +SnoopFilter::finishRequest(bool will_retry, const Packet* cpkt) { - DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n", - __func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString()); - - // Ultimately we should check if the packet came from an - // allocating source, not just if the port is snooping - bool allocate = !cpkt->req->isUncacheable() && slave_port.isSnooping(); - if (!allocate) - return; + if (reqLookupResult != cachedLocations.end()) { + // since we rely on the caller, do a basic check to ensure + // that finishRequest is being called following lookupRequest + assert(reqLookupResult->first == cpkt->getBlockAddr(linesize)); + if (will_retry) { + // Undo any changes made in lookupRequest to the snoop filter + // entry if the request will come again. retryItem holds + // the previous value of the snoopfilter entry. + reqLookupResult->second = retryItem; + + DPRINTF(SnoopFilter, "%s: restored SF value %x.%x\n", + __func__, retryItem.requested, retryItem.holder); + } - Addr line_addr = cpkt->getBlockAddr(linesize); - auto sf_it = cachedLocations.find(line_addr); - assert(sf_it != cachedLocations.end()); - if (will_retry) { - // Undo any changes made in lookupRequest to the snoop filter - // entry if the request will come again. retryItem holds - // the previous value of the snoopfilter entry. - sf_it->second = retryItem; - - DPRINTF(SnoopFilter, "%s: restored SF value %x.%x\n", - __func__, retryItem.requested, retryItem.holder); + eraseIfNullEntry(reqLookupResult); } - - eraseIfNullEntry(sf_it); } std::pair -- cgit v1.2.3