0fcb376e5f
This patch changes the name of a bunch of packet flags and MSHR member functions and variables to make the coherency protocol easier to understand. In addition the patch adds and updates lots of descriptions, explicitly spelling out assumptions. The following name changes are made: * the packet memInhibit flag is renamed to cacheResponding * the packet sharedAsserted flag is renamed to hasSharers * the packet NeedsExclusive attribute is renamed to NeedsWritable * the packet isSupplyExclusive is renamed responderHadWritable * the MSHR pendingDirty is renamed to pendingModified The cache states, Modified, Owned, Exclusive, Shared are also called out in the cache and MSHR code to make it easier to understand.
438 lines
14 KiB
C++
438 lines
14 KiB
C++
/*
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* Copyright (c) 2011-2013 ARM Limited
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* All rights reserved
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*
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* The license below extends only to copyright in the software and shall
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* not be construed as granting a license to any other intellectual
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* property including but not limited to intellectual property relating
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* to a hardware implementation of the functionality of the software
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* licensed hereunder. You may use the software subject to the license
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* terms below provided that you ensure that this notice is replicated
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* unmodified and in its entirety in all distributions of the software,
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* modified or unmodified, in source code or in binary form.
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*
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* Copyright (c) 2006 The Regents of The University of Michigan
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* Copyright (c) 2015 The University of Bologna
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Ali Saidi
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* Steve Reinhardt
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* Andreas Hansson
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* Erfan Azarkhish
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*/
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/**
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* @file
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* Implementation of the SerialLink Class, modeling Hybrid-Memory-Cube's
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* serial interface.
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*/
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#include "mem/serial_link.hh"
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#include "base/trace.hh"
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#include "debug/SerialLink.hh"
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#include "params/SerialLink.hh"
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SerialLink::SerialLinkSlavePort::SerialLinkSlavePort(const std::string& _name,
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SerialLink& _serial_link,
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SerialLinkMasterPort& _masterPort,
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Cycles _delay, int _resp_limit,
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const std::vector<AddrRange>&
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_ranges)
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: SlavePort(_name, &_serial_link), serial_link(_serial_link),
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masterPort(_masterPort), delay(_delay),
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ranges(_ranges.begin(), _ranges.end()),
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outstandingResponses(0), retryReq(false),
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respQueueLimit(_resp_limit), sendEvent(*this)
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{
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}
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SerialLink::SerialLinkMasterPort::SerialLinkMasterPort(const std::string&
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_name, SerialLink& _serial_link,
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SerialLinkSlavePort& _slavePort,
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Cycles _delay, int _req_limit)
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: MasterPort(_name, &_serial_link), serial_link(_serial_link),
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slavePort(_slavePort), delay(_delay), reqQueueLimit(_req_limit),
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sendEvent(*this)
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{
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}
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SerialLink::SerialLink(SerialLinkParams *p)
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: MemObject(p),
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slavePort(p->name + ".slave", *this, masterPort,
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ticksToCycles(p->delay), p->resp_size, p->ranges),
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masterPort(p->name + ".master", *this, slavePort,
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ticksToCycles(p->delay), p->req_size),
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num_lanes(p->num_lanes)
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{
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}
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BaseMasterPort&
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SerialLink::getMasterPort(const std::string &if_name, PortID idx)
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{
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if (if_name == "master")
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return masterPort;
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else
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// pass it along to our super class
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return MemObject::getMasterPort(if_name, idx);
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}
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BaseSlavePort&
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SerialLink::getSlavePort(const std::string &if_name, PortID idx)
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{
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if (if_name == "slave")
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return slavePort;
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else
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// pass it along to our super class
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return MemObject::getSlavePort(if_name, idx);
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}
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void
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SerialLink::init()
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{
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// make sure both sides are connected and have the same block size
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if (!slavePort.isConnected() || !masterPort.isConnected())
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fatal("Both ports of a serial_link must be connected.\n");
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// notify the master side of our address ranges
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slavePort.sendRangeChange();
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}
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bool
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SerialLink::SerialLinkSlavePort::respQueueFull() const
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{
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return outstandingResponses == respQueueLimit;
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}
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bool
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SerialLink::SerialLinkMasterPort::reqQueueFull() const
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{
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return transmitList.size() == reqQueueLimit;
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}
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bool
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SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt)
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{
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// all checks are done when the request is accepted on the slave
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// side, so we are guaranteed to have space for the response
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DPRINTF(SerialLink, "recvTimingResp: %s addr 0x%x\n",
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pkt->cmdString(), pkt->getAddr());
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DPRINTF(SerialLink, "Request queue size: %d\n", transmitList.size());
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// @todo: We need to pay for this and not just zero it out
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pkt->headerDelay = pkt->payloadDelay = 0;
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// This is similar to what happens for the request packets:
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// The serializer will start serialization as soon as it receives the
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// first flit, but the deserializer (at the host side in this case), will
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// have to wait to receive the whole packet. So we only account for the
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// deserialization latency.
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Cycles cycles = delay;
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cycles += Cycles(divCeil(pkt->getSize() * 8, serial_link.num_lanes));
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Tick t = serial_link.clockEdge(cycles);
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//@todo: If the processor sends two uncached requests towards HMC and the
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// second one is smaller than the first one. It may happen that the second
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// one crosses this link faster than the first one (because the packet
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// waits in the link based on its size). This can reorder the received
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// response.
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slavePort.schedTimingResp(pkt, t);
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return true;
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}
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bool
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SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt)
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{
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DPRINTF(SerialLink, "recvTimingReq: %s addr 0x%x\n",
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pkt->cmdString(), pkt->getAddr());
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// we should not see a timing request if we are already in a retry
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assert(!retryReq);
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DPRINTF(SerialLink, "Response queue size: %d outresp: %d\n",
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transmitList.size(), outstandingResponses);
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// if the request queue is full then there is no hope
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if (masterPort.reqQueueFull()) {
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DPRINTF(SerialLink, "Request queue full\n");
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retryReq = true;
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} else if ( !retryReq ) {
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// look at the response queue if we expect to see a response
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bool expects_response = pkt->needsResponse() &&
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!pkt->cacheResponding();
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if (expects_response) {
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if (respQueueFull()) {
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DPRINTF(SerialLink, "Response queue full\n");
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retryReq = true;
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} else {
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// ok to send the request with space for the response
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DPRINTF(SerialLink, "Reserving space for response\n");
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assert(outstandingResponses != respQueueLimit);
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++outstandingResponses;
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// no need to set retryReq to false as this is already the
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// case
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}
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}
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if (!retryReq) {
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// @todo: We need to pay for this and not just zero it out
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pkt->headerDelay = pkt->payloadDelay = 0;
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// We assume that the serializer component at the transmitter side
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// does not need to receive the whole packet to start the
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// serialization (this assumption is consistent with the HMC
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// standard). But the deserializer waits for the complete packet
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// to check its integrity first. So everytime a packet crosses a
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// serial link, we should account for its deserialization latency
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// only.
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Cycles cycles = delay;
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cycles += Cycles(divCeil(pkt->getSize() * 8,
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serial_link.num_lanes));
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Tick t = serial_link.clockEdge(cycles);
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//@todo: If the processor sends two uncached requests towards HMC
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// and the second one is smaller than the first one. It may happen
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// that the second one crosses this link faster than the first one
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// (because the packet waits in the link based on its size).
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// This can reorder the received response.
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masterPort.schedTimingReq(pkt, t);
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}
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}
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// remember that we are now stalling a packet and that we have to
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// tell the sending master to retry once space becomes available,
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// we make no distinction whether the stalling is due to the
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// request queue or response queue being full
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return !retryReq;
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}
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void
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SerialLink::SerialLinkSlavePort::retryStalledReq()
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{
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if (retryReq) {
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DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
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retryReq = false;
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sendRetryReq();
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}
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}
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void
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SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
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{
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// If we're about to put this packet at the head of the queue, we
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// need to schedule an event to do the transmit. Otherwise there
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// should already be an event scheduled for sending the head
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// packet.
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if (transmitList.empty()) {
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serial_link.schedule(sendEvent, when);
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}
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assert(transmitList.size() != reqQueueLimit);
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transmitList.emplace_back(DeferredPacket(pkt, when));
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}
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void
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SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
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{
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// If we're about to put this packet at the head of the queue, we
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// need to schedule an event to do the transmit. Otherwise there
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// should already be an event scheduled for sending the head
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// packet.
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if (transmitList.empty()) {
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serial_link.schedule(sendEvent, when);
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}
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transmitList.emplace_back(DeferredPacket(pkt, when));
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}
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void
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SerialLink::SerialLinkMasterPort::trySendTiming()
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{
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assert(!transmitList.empty());
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DeferredPacket req = transmitList.front();
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assert(req.tick <= curTick());
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PacketPtr pkt = req.pkt;
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DPRINTF(SerialLink, "trySend request addr 0x%x, queue size %d\n",
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pkt->getAddr(), transmitList.size());
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if (sendTimingReq(pkt)) {
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// send successful
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transmitList.pop_front();
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DPRINTF(SerialLink, "trySend request successful\n");
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// If there are more packets to send, schedule event to try again.
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if (!transmitList.empty()) {
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DeferredPacket next_req = transmitList.front();
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DPRINTF(SerialLink, "Scheduling next send\n");
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// Make sure bandwidth limitation is met
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Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
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serial_link.num_lanes));
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Tick t = serial_link.clockEdge(cycles);
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serial_link.schedule(sendEvent, std::max(next_req.tick, t));
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}
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// if we have stalled a request due to a full request queue,
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// then send a retry at this point, also note that if the
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// request we stalled was waiting for the response queue
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// rather than the request queue we might stall it again
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slavePort.retryStalledReq();
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}
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// if the send failed, then we try again once we receive a retry,
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// and therefore there is no need to take any action
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}
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void
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SerialLink::SerialLinkSlavePort::trySendTiming()
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{
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assert(!transmitList.empty());
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DeferredPacket resp = transmitList.front();
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assert(resp.tick <= curTick());
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PacketPtr pkt = resp.pkt;
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DPRINTF(SerialLink, "trySend response addr 0x%x, outstanding %d\n",
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pkt->getAddr(), outstandingResponses);
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if (sendTimingResp(pkt)) {
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// send successful
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transmitList.pop_front();
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DPRINTF(SerialLink, "trySend response successful\n");
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assert(outstandingResponses != 0);
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--outstandingResponses;
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// If there are more packets to send, schedule event to try again.
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if (!transmitList.empty()) {
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DeferredPacket next_resp = transmitList.front();
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DPRINTF(SerialLink, "Scheduling next send\n");
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// Make sure bandwidth limitation is met
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Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
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serial_link.num_lanes));
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Tick t = serial_link.clockEdge(cycles);
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serial_link.schedule(sendEvent, std::max(next_resp.tick, t));
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}
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// if there is space in the request queue and we were stalling
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// a request, it will definitely be possible to accept it now
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// since there is guaranteed space in the response queue
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if (!masterPort.reqQueueFull() && retryReq) {
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DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
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retryReq = false;
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sendRetryReq();
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}
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}
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// if the send failed, then we try again once we receive a retry,
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// and therefore there is no need to take any action
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}
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void
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SerialLink::SerialLinkMasterPort::recvReqRetry()
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{
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trySendTiming();
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}
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void
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SerialLink::SerialLinkSlavePort::recvRespRetry()
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{
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trySendTiming();
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}
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Tick
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SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt)
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{
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return delay * serial_link.clockPeriod() + masterPort.sendAtomic(pkt);
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}
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void
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SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt)
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{
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pkt->pushLabel(name());
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// check the response queue
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for (auto i = transmitList.begin(); i != transmitList.end(); ++i) {
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if (pkt->checkFunctional((*i).pkt)) {
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pkt->makeResponse();
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return;
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}
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}
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// also check the master port's request queue
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if (masterPort.checkFunctional(pkt)) {
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return;
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}
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pkt->popLabel();
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// fall through if pkt still not satisfied
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masterPort.sendFunctional(pkt);
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}
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bool
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SerialLink::SerialLinkMasterPort::checkFunctional(PacketPtr pkt)
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{
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bool found = false;
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auto i = transmitList.begin();
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while(i != transmitList.end() && !found) {
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if (pkt->checkFunctional((*i).pkt)) {
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pkt->makeResponse();
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found = true;
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}
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++i;
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}
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return found;
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}
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AddrRangeList
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SerialLink::SerialLinkSlavePort::getAddrRanges() const
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{
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return ranges;
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}
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SerialLink *
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SerialLinkParams::create()
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{
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return new SerialLink(this);
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}
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