| /* |
| * Copyright (c) 2013 ARM Limited |
| * All rights reserved |
| * |
| * The license below extends only to copyright in the software and shall |
| * not be construed as granting a license to any other intellectual |
| * property including but not limited to intellectual property relating |
| * to a hardware implementation of the functionality of the software |
| * licensed hereunder. You may use the software subject to the license |
| * terms below provided that you ensure that this notice is replicated |
| * unmodified and in its entirety in all distributions of the software, |
| * modified or unmodified, in source code or in binary form. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer; |
| * redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution; |
| * neither the name of the copyright holders nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * Authors: Stephan Diestelhorst <stephan.diestelhorst@arm.com> |
| */ |
| |
| /** |
| * @file |
| * Definition of a snoop filter. |
| */ |
| |
| #ifndef __MEM_SNOOP_FILTER_HH__ |
| #define __MEM_SNOOP_FILTER_HH__ |
| |
| #include <utility> |
| |
| #include "base/hashmap.hh" |
| #include "mem/packet.hh" |
| #include "mem/port.hh" |
| #include "mem/qport.hh" |
| #include "params/SnoopFilter.hh" |
| #include "sim/sim_object.hh" |
| #include "sim/system.hh" |
| |
| /** |
| * This snoop filter keeps track of which connected port has a |
| * particular line of data. It can be queried (through lookup*) on |
| * memory requests from above (reads / writes / ...); and also from |
| * below (snoops). The snoop filter precisely knows about the location |
| * of lines "above" it through a map from cache line address to |
| * sharers/ports. The snoop filter ties into the flows of requests |
| * (when they succeed at the lower interface), regular responses from |
| * below and also responses from sideway's caches (in update*). This |
| * allows the snoop filter to model cache-line residency by snooping |
| * the messages. |
| * |
| * The tracking happens in two fields to be able to distinguish |
| * between in-flight requests (in requested) and already pulled in |
| * lines (in holder). This distinction is used for producing tighter |
| * assertions and tracking request completion. For safety, (requested |
| * | holder) should be notified and the requesting MSHRs will take |
| * care of ordering. |
| * |
| * Overall, some trickery is required because: |
| * (1) snoops are not followed by an ACK, but only evoke a response if |
| * they need to (hit dirty) |
| * (2) side-channel information is funnelled through direct modifications of |
| * pkt, instead of proper messages through the bus |
| * (3) there are no clean evict messages telling the snoop filter that a local, |
| * upper cache dropped a line, making the snoop filter pessimistic for now |
| * (4) ordering: there is no single point of order in the system. Instead, |
| * requesting MSHRs track order between local requests and remote snoops |
| */ |
| class SnoopFilter : public SimObject { |
| public: |
| typedef std::vector<QueuedSlavePort*> SnoopList; |
| |
| SnoopFilter (const SnoopFilterParams *p) : SimObject(p), |
| linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency) |
| { |
| } |
| |
| /** |
| * Init a new snoop filter and tell it about all the slave ports of the |
| * enclosing bus. |
| * |
| * @param bus_slave_ports Vector of slave ports that the bus is attached to. |
| */ |
| void setSlavePorts(const SnoopList& bus_slave_ports) { |
| slavePorts = bus_slave_ports; |
| } |
| |
| /** |
| * Lookup a request (from a slave port) in the snoop filter and return a |
| * list of other slave ports that need forwarding of the resulting snoops. |
| * Additionally, update the tracking structures with new request |
| * information. |
| * |
| * @param cpkt Pointer to the request packet. Not changed. |
| * @param slave_port Slave port where the request came from. |
| * @return Pair of a vector of snoop target ports and lookup latency. |
| */ |
| std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt, |
| const SlavePort& slave_port); |
| |
| /** |
| * For a successful request, update all data structures in the snoop filter |
| * reflecting the changes caused by that request |
| * |
| * @param cpkt Pointer to the request packet. Not changed. |
| * @param slave_port Slave port where the request came from. |
| * @param will_retry This request will retry on this bus / snoop filter |
| */ |
| void updateRequest(const Packet* cpkt, const SlavePort& slave_port, |
| bool will_retry); |
| |
| /** |
| * Handle an incoming snoop from below (the master port). These can upgrade the |
| * tracking logic and may also benefit from additional steering thanks to the |
| * snoop filter. |
| * @param cpkt Pointer to const Packet containing the snoop. |
| * @return Pair with a vector of SlavePorts that need snooping and a lookup |
| * latency. |
| */ |
| std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt); |
| |
| /** |
| * Let the snoop filter see any snoop responses that turn into request responses |
| * and indicate cache to cache transfers. These will update the corresponding |
| * state in the filter. |
| * |
| * @param cpkt Pointer to const Packet holding the snoop response. |
| * @param rsp_port SlavePort that sends the response. |
| * @param req_port SlavePort that made the original request and is the |
| * destination of the snoop response. |
| */ |
| void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port, |
| const SlavePort& req_port); |
| |
| /** |
| * Pass snoop responses that travel downward through the snoop filter and let |
| * them update the snoop filter state. No additional routing happens. |
| * |
| * @param cpkt Pointer to const Packet holding the snoop response. |
| * @param rsp_port SlavePort that sends the response. |
| * @param req_port MasterPort through which the response leaves this cluster. |
| */ |
| void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port, |
| const MasterPort& req_port); |
| |
| /** |
| * Update the snoop filter with a response from below (outer / other cache, |
| * or memory) and update the tracking information in the snoop filter. |
| * |
| * @param cpkt Pointer to const Packet holding the snoop response. |
| * @param slave_port SlavePort that made the original request and is the target |
| * of this response. |
| */ |
| void updateResponse(const Packet *cpkt, const SlavePort& slave_port); |
| |
| /** |
| * Simple factory methods for standard return values for lookupRequest |
| */ |
| std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const |
| { |
| return std::make_pair(slavePorts, latency); |
| } |
| std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports, |
| Cycles latency) const |
| { |
| return std::make_pair(slave_ports, latency); |
| } |
| std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const |
| { |
| SnoopList empty; |
| return std::make_pair(empty , latency); |
| } |
| |
| virtual void regStats(); |
| |
| protected: |
| typedef uint64_t SnoopMask; |
| /** |
| * Per cache line item tracking a bitmask of SlavePorts who have an |
| * outstanding request to this line (requested) or already share a cache line |
| * with this address (holder). |
| */ |
| struct SnoopItem { |
| SnoopMask requested; |
| SnoopMask holder; |
| }; |
| /** |
| * Convert a single port to a corresponding, one-hot bitmask |
| * @param port SlavePort that should be converted. |
| * @return One-hot bitmask corresponding to the port. |
| */ |
| SnoopMask portToMask(const SlavePort& port) const; |
| /** |
| * Convert multiple ports to a corresponding bitmask |
| * @param ports SnoopList that should be converted. |
| * @return Bitmask corresponding to the ports in the list. |
| */ |
| SnoopMask portListToMask(const SnoopList& ports) const; |
| /** |
| * Converts a bitmask of ports into the corresponing list of ports |
| * @param ports SnoopMask of the requested ports |
| * @return SnoopList containing all the requested SlavePorts |
| */ |
| SnoopList maskToPortList(SnoopMask ports) const; |
| |
| private: |
| /** Simple hash set of cached addresses. */ |
| m5::hash_map<Addr, SnoopItem> cachedLocations; |
| /** List of all attached slave ports. */ |
| SnoopList slavePorts; |
| /** Cache line size. */ |
| const unsigned linesize; |
| /** Latency for doing a lookup in the filter */ |
| const Cycles lookupLatency; |
| |
| /** Statistics */ |
| Stats::Scalar totRequests; |
| Stats::Scalar hitSingleRequests; |
| Stats::Scalar hitMultiRequests; |
| |
| Stats::Scalar totSnoops; |
| Stats::Scalar hitSingleSnoops; |
| Stats::Scalar hitMultiSnoops; |
| }; |
| |
| inline SnoopFilter::SnoopMask |
| SnoopFilter::portToMask(const SlavePort& port) const |
| { |
| unsigned id = (unsigned)port.getId(); |
| assert(id != (unsigned)InvalidPortID); |
| assert((int)id < 8 * sizeof(SnoopMask)); |
| |
| return ((SnoopMask)1) << id; |
| } |
| |
| inline SnoopFilter::SnoopMask |
| SnoopFilter::portListToMask(const SnoopList& ports) const |
| { |
| SnoopMask m = 0; |
| for (auto port = ports.begin(); port != ports.end(); ++port) |
| m |= portToMask(**port); |
| return m; |
| } |
| |
| inline SnoopFilter::SnoopList |
| SnoopFilter::maskToPortList(SnoopMask port_mask) const |
| { |
| SnoopList res; |
| for (auto port = slavePorts.begin(); port != slavePorts.end(); ++port) |
| if (port_mask & portToMask(**port)) |
| res.push_back(*port); |
| return res; |
| } |
| #endif // __MEM_SNOOP_FILTER_HH__ |