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Diffstat (limited to 'src/mem/snoop_filter.cc')
| -rwxr-xr-x | src/mem/snoop_filter.cc | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/src/mem/snoop_filter.cc b/src/mem/snoop_filter.cc new file mode 100755 index 000000000..1acfbef6c --- /dev/null +++ b/src/mem/snoop_filter.cc @@ -0,0 +1,274 @@ +/* + * 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. + */ + +#include "base/misc.hh" +#include "base/trace.hh" +#include "debug/SnoopFilter.hh" +#include "mem/snoop_filter.hh" +#include "sim/system.hh" + +std::pair<SnoopFilter::SnoopList, Cycles> +SnoopFilter::lookupRequest(const Packet* cpkt, const SlavePort& slave_port) +{ + DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n", + __func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString()); + + Addr line_addr = cpkt->getAddr() & ~(linesize - 1); + SnoopMask req_port = portToMask(slave_port); + SnoopItem& sf_item = cachedLocations[line_addr]; + + DPRINTF(SnoopFilter, "%s: SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + + if (cpkt->needsResponse()) { + if (!cpkt->memInhibitAsserted()) { + // Max one request per address per port + panic_if(sf_item.requested & req_port, "double request :( "\ + "SF value %x.%x\n", sf_item.requested, sf_item.holder); + + // Mark in-flight requests to distinguish later on + sf_item.requested |= req_port; + } else { + // NOTE: The memInhibit might have been asserted by a cache closer + // to the CPU, already -> the response will not be seen by this + // filter -> we do not need to keep the in-flight request, but make + // sure that we know that that cluster has a copy + panic_if(!(sf_item.holder & req_port), "Need to hold the value!"); + DPRINTF(SnoopFilter, "%s: not marking request. SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + } + DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + } + SnoopMask interested = (sf_item.holder | sf_item.requested) & ~req_port; + return snoopSelected(maskToPortList(interested), lookupLatency); +} + +void +SnoopFilter::updateRequest(const Packet* cpkt, const SlavePort& slave_port, + bool will_retry) +{ + DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n", + __func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString()); + + Addr line_addr = cpkt->getAddr() & ~(linesize - 1); + SnoopMask req_port = portToMask(slave_port); + SnoopItem& sf_item = cachedLocations[line_addr]; + + DPRINTF(SnoopFilter, "%s: old SF value %x.%x retry: %i\n", + __func__, sf_item.requested, sf_item.holder, will_retry); + + if (will_retry) { + // Unmark a request that will come again. + sf_item.requested &= ~req_port; + return; + } + + // will_retry == false + if (!cpkt->needsResponse()) { + // Packets that will not evoke a response but still need updates of the + // snoop filter; WRITEBACKs for now only + if (cpkt->cmd == MemCmd::Writeback) { + // make sure that the sender actually had the line + panic_if(sf_item.requested & req_port, "double request :( "\ + "SF value %x.%x\n", sf_item.requested, sf_item.holder); + panic_if(!(sf_item.holder & req_port), "requester %x is not a "\ + "holder :( SF value %x.%x\n", req_port, + sf_item.requested, sf_item.holder); + // Writebacks -> the sender does not have the line anymore + sf_item.holder &= ~req_port; + } else { + assert(0 == "Handle non-writeback, here"); + } + DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + } +} + +std::pair<SnoopFilter::SnoopList, Cycles> +SnoopFilter::lookupSnoop(const Packet* cpkt) +{ + DPRINTF(SnoopFilter, "%s: packet addr 0x%x cmd %s\n", + __func__, cpkt->getAddr(), cpkt->cmdString()); + + 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->getAddr() & ~(linesize - 1); + SnoopItem& sf_item = cachedLocations[line_addr]; + + DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + + SnoopMask interested = (sf_item.holder | sf_item.requested); + assert(cpkt->isInvalidate() == cpkt->needsExclusive()); + if (cpkt->isInvalidate() && !sf_item.requested) { + // Early clear of the holder, if no other request is currently going on + // @todo: This should possibly be updated even though we do not filter + // upward snoops + sf_item.holder = 0; + } + + DPRINTF(SnoopFilter, "%s: new SF value %x.%x interest: %x \n", + __func__, sf_item.requested, sf_item.holder, interested); + + return snoopSelected(maskToPortList(interested), lookupLatency); +} + +void +SnoopFilter::updateSnoopResponse(const Packet* cpkt, + const SlavePort& rsp_port, + const SlavePort& req_port) +{ + DPRINTF(SnoopFilter, "%s: packet rsp %s req %s addr 0x%x cmd %s\n", + __func__, rsp_port.name(), req_port.name(), cpkt->getAddr(), + cpkt->cmdString()); + + Addr line_addr = cpkt->getAddr() & ~(linesize - 1); + SnoopMask rsp_mask = portToMask(rsp_port); + SnoopMask req_mask = portToMask(req_port); + SnoopItem& sf_item = cachedLocations[line_addr]; + + assert(cpkt->isResponse()); + assert(cpkt->memInhibitAsserted()); + + DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + + // The source should have the line + panic_if(!(sf_item.holder & rsp_mask), "SF value %x.%x does not have "\ + "the line\n", sf_item.requested, sf_item.holder); + + // The destination should have had a request in + panic_if(!(sf_item.requested & req_mask), "SF value %x.%x missing "\ + "the original request\n", sf_item.requested, sf_item.holder); + + // Update the residency of the cache line. + if (cpkt->needsExclusive() || !cpkt->sharedAsserted()) { + DPRINTF(SnoopFilter, "%s: dropping %x because needs: %i shared: %i "\ + "SF val: %x.%x\n", __func__, rsp_mask, + cpkt->needsExclusive(), cpkt->sharedAsserted(), + sf_item.requested, sf_item.holder); + + sf_item.holder &= ~rsp_mask; + // The snoop filter does not see any ACKs from non-responding sharers + // that have been invalidated :( So below assert would be nice, but.. + //assert(sf_item.holder == 0); + sf_item.holder = 0; + } + assert(cpkt->cmd != MemCmd::Writeback); + sf_item.holder |= req_mask; + sf_item.requested &= ~req_mask; + DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); +} + +void +SnoopFilter::updateSnoopForward(const Packet* cpkt, + const SlavePort& rsp_port, const MasterPort& req_port) +{ + DPRINTF(SnoopFilter, "%s: packet rsp %s req %s addr 0x%x cmd %s\n", + __func__, rsp_port.name(), req_port.name(), cpkt->getAddr(), + cpkt->cmdString()); + + Addr line_addr = cpkt->getAddr() & ~(linesize - 1); + SnoopItem& sf_item = cachedLocations[line_addr]; + 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. + if (cpkt->needsExclusive()) { + // 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; + } + DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); +} + +void +SnoopFilter::updateResponse(const Packet* cpkt, const SlavePort& slave_port) +{ + DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n", + __func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString()); + + Addr line_addr = cpkt->getAddr() & ~(linesize - 1); + SnoopMask slave_mask = portToMask(slave_port); + SnoopItem& sf_item = cachedLocations[line_addr]; + + assert(cpkt->isResponse()); + + DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); + + // Make sure we have seen the actual request, too + panic_if(!(sf_item.requested & slave_mask), "SF value %x.%x missing "\ + "request bit\n", sf_item.requested, sf_item.holder); + + // Update the residency of the cache line. + if (cpkt->needsExclusive() || !cpkt->sharedAsserted()) + sf_item.holder = 0; + sf_item.holder |= slave_mask; + sf_item.requested &= ~slave_mask; + DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n", + __func__, sf_item.requested, sf_item.holder); +} + +SnoopFilter * +SnoopFilterParams::create() +{ + return new SnoopFilter(this); +} |