1/* 2 * Copyright (c) 2013-2015 ARM Limited 3 * All rights reserved 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software --- 20 unchanged lines hidden (view full) --- 29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 * |
37 * Authors: Stephan Diestelhorst |
38 */ 39 40/** 41 * @file 42 * Definition of a snoop filter. 43 */ 44 45#ifndef __MEM_SNOOP_FILTER_HH__ --- 45 unchanged lines hidden (view full) --- 91 SnoopFilter (const SnoopFilterParams *p) : 92 SimObject(p), reqLookupResult(cachedLocations.end()), retryItem{0, 0}, 93 linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency), 94 maxEntryCount(p->max_capacity / p->system->cacheLineSize()) 95 { 96 } 97 98 /** |
99 * Init a new snoop filter and tell it about all the slave ports 100 * of the enclosing bus. |
101 * 102 * @param slave_ports Slave ports that the bus is attached to. 103 */ 104 void setSlavePorts(const SnoopList& slave_ports) { 105 localSlavePortIds.resize(slave_ports.size(), InvalidPortID); 106 107 PortID id = 0; 108 for (const auto& p : slave_ports) { --- 13 unchanged lines hidden (view full) --- 122 /** 123 * Lookup a request (from a slave port) in the snoop filter and 124 * return a list of other slave ports that need forwarding of the 125 * resulting snoops. Additionally, update the tracking structures 126 * with new request information. Note that the caller must also 127 * call finishRequest once it is known if the request needs to 128 * retry or not. 129 * |
130 * @param cpkt Pointer to the request packet. Not changed. |
131 * @param slave_port Slave port where the request came from. 132 * @return Pair of a vector of snoop target ports and lookup latency. 133 */ 134 std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt, 135 const SlavePort& slave_port); 136 137 /** 138 * For an un-successful request, revert the change to the snoop 139 * filter. Also take care of erasing any null entries. This method 140 * relies on the result from lookupRequest being stored in 141 * reqLookupResult. 142 * 143 * @param will_retry This request will retry on this bus / snoop filter |
144 * @param cpkt Request packet, merely for sanity checking |
145 */ 146 void finishRequest(bool will_retry, const Packet* cpkt); 147 148 /** |
149 * Handle an incoming snoop from below (the master port). These 150 * can upgrade the tracking logic and may also benefit from 151 * additional steering thanks to the snoop filter. 152 * |
153 * @param cpkt Pointer to const Packet containing the snoop. 154 * @return Pair with a vector of SlavePorts that need snooping and a lookup 155 * latency. 156 */ 157 std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt); 158 159 /** |
160 * Let the snoop filter see any snoop responses that turn into 161 * request responses and indicate cache to cache transfers. These 162 * will update the corresponding state in the filter. |
163 * 164 * @param cpkt Pointer to const Packet holding the snoop response. 165 * @param rsp_port SlavePort that sends the response. 166 * @param req_port SlavePort that made the original request and is the 167 * destination of the snoop response. 168 */ 169 void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port, 170 const SlavePort& req_port); 171 172 /** |
173 * Pass snoop responses that travel downward through the snoop 174 * filter and let them update the snoop filter state. No 175 * additional routing happens. |
176 * 177 * @param cpkt Pointer to const Packet holding the snoop response. 178 * @param rsp_port SlavePort that sends the response. |
179 * @param req_port MasterPort through which the response is forwarded. |
180 */ 181 void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port, 182 const MasterPort& req_port); 183 184 /** |
185 * Update the snoop filter with a response from below (outer / 186 * other cache, or memory) and update the tracking information in 187 * the snoop filter. |
188 * 189 * @param cpkt Pointer to const Packet holding the snoop response. |
190 * @param slave_port SlavePort that made the original request and 191 * is the target of this response. |
192 */ 193 void updateResponse(const Packet *cpkt, const SlavePort& slave_port); 194 |
195 virtual void regStats(); 196 197 protected: 198 |
199 /** |
200 * The underlying type for the bitmask we use for tracking. This 201 * limits the number of snooping ports supported per crossbar. For 202 * the moment it is an uint64_t to offer maximum 203 * scalability. However, it is possible to use e.g. a uint16_t or 204 * uint32_to slim down the footprint of the hash map (and 205 * ultimately improve the simulation performance). |
206 */ |
207 typedef uint64_t SnoopMask; 208 209 /** 210 * Per cache line item tracking a bitmask of SlavePorts who have an 211 * outstanding request to this line (requested) or already share a 212 * cache line with this address (holder). 213 */ 214 struct SnoopItem { 215 SnoopMask requested; 216 SnoopMask holder; 217 }; 218 /** 219 * HashMap of SnoopItems indexed by line address 220 */ 221 typedef m5::hash_map<Addr, SnoopItem> SnoopFilterCache; 222 223 /** 224 * Simple factory methods for standard return values. 225 */ |
226 std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const 227 { 228 return std::make_pair(slavePorts, latency); 229 } 230 std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports, 231 Cycles latency) const 232 { 233 return std::make_pair(slave_ports, latency); 234 } 235 std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const 236 { 237 SnoopList empty; 238 return std::make_pair(empty , latency); 239 } 240 |
241 /** |
242 * Convert a single port to a corresponding, one-hot bitmask 243 * @param port SlavePort that should be converted. 244 * @return One-hot bitmask corresponding to the port. 245 */ 246 SnoopMask portToMask(const SlavePort& port) const; 247 /** 248 * Converts a bitmask of ports into the corresponing list of ports 249 * @param ports SnoopMask of the requested ports 250 * @return SnoopList containing all the requested SlavePorts 251 */ 252 SnoopList maskToPortList(SnoopMask ports) const; 253 254 private: 255 256 /** 257 * Removes snoop filter items which have no requesters and no holders. 258 */ 259 void eraseIfNullEntry(SnoopFilterCache::iterator& sf_it); |
260 |
261 /** Simple hash set of cached addresses. */ 262 SnoopFilterCache cachedLocations; 263 /** 264 * Iterator used to store the result from lookupRequest until we 265 * call finishRequest. 266 */ 267 SnoopFilterCache::iterator reqLookupResult; 268 /** --- 36 unchanged lines hidden (view full) --- 305SnoopFilter::maskToPortList(SnoopMask port_mask) const 306{ 307 SnoopList res; 308 for (const auto& p : slavePorts) 309 if (port_mask & portToMask(*p)) 310 res.push_back(p); 311 return res; 312} |
313 |
314#endif // __MEM_SNOOP_FILTER_HH__ |