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/*
* Copyright (c) 2011-2015, 2018-2020 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.
*
* Copyright (c) 2006 The Regents of The University of Michigan
* All rights reserved.
*
* 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.
*
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* 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,
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* @file
* Definition of a crossbar object.
*/
#include "mem/xbar.hh"
#include "base/logging.hh"
#include "base/trace.hh"
#include "debug/AddrRanges.hh"
#include "debug/Drain.hh"
#include "debug/XBar.hh"
namespace gem5
{
BaseXBar::BaseXBar(const BaseXBarParams &p)
: ClockedObject(p),
frontendLatency(p.frontend_latency),
forwardLatency(p.forward_latency),
responseLatency(p.response_latency),
headerLatency(p.header_latency),
width(p.width),
gotAddrRanges(p.port_default_connection_count +
p.port_mem_side_ports_connection_count, false),
gotAllAddrRanges(false), defaultPortID(InvalidPortID),
useDefaultRange(p.use_default_range),
ADD_STAT(transDist, statistics::units::Count::get(),
"Transaction distribution"),
ADD_STAT(pktCount, statistics::units::Count::get(),
"Packet count per connected requestor and responder"),
ADD_STAT(pktSize, statistics::units::Byte::get(),
"Cumulative packet size per connected requestor and responder")
{
}
BaseXBar::~BaseXBar()
{
for (auto port: memSidePorts)
delete port;
for (auto port: cpuSidePorts)
delete port;
}
Port &
BaseXBar::getPort(const std::string &if_name, PortID idx)
{
if (if_name == "mem_side_ports" && idx < memSidePorts.size()) {
// the memory-side ports index translates directly to the vector
// position
return *memSidePorts[idx];
} else if (if_name == "default") {
return *memSidePorts[defaultPortID];
} else if (if_name == "cpu_side_ports" && idx < cpuSidePorts.size()) {
// the CPU-side ports index translates directly to the vector position
return *cpuSidePorts[idx];
} else {
return ClockedObject::getPort(if_name, idx);
}
}
void
BaseXBar::calcPacketTiming(PacketPtr pkt, Tick header_delay)
{
// the crossbar will be called at a time that is not necessarily
// coinciding with its own clock, so start by determining how long
// until the next clock edge (could be zero)
Tick offset = clockEdge() - curTick();
// the header delay depends on the path through the crossbar, and
// we therefore rely on the caller to provide the actual
// value
pkt->headerDelay += offset + header_delay;
// note that we add the header delay to the existing value, and
// align it to the crossbar clock
// do a quick sanity check to ensure the timings are not being
// ignored, note that this specific value may cause problems for
// slower interconnects
panic_if(pkt->headerDelay > sim_clock::as_int::us,
"Encountered header delay exceeding 1 us\n");
if (pkt->hasData()) {
// the payloadDelay takes into account the relative time to
// deliver the payload of the packet, after the header delay,
// we take the maximum since the payload delay could already
// be longer than what this parcitular crossbar enforces.
pkt->payloadDelay = std::max<Tick>(pkt->payloadDelay,
divCeil(pkt->getSize(), width) *
clockPeriod());
}
// the payload delay is not paying for the clock offset as that is
// already done using the header delay, and the payload delay is
// also used to determine how long the crossbar layer is busy and
// thus regulates throughput
}
template <typename SrcType, typename DstType>
BaseXBar::Layer<SrcType, DstType>::Layer(DstType& _port, BaseXBar& _xbar,
const std::string& _name) :
statistics::Group(&_xbar, _name.c_str()),
port(_port), xbar(_xbar), _name(xbar.name() + "." + _name), state(IDLE),
waitingForPeer(NULL), releaseEvent([this]{ releaseLayer(); }, name()),
ADD_STAT(occupancy, statistics::units::Tick::get(), "Layer occupancy (ticks)"),
ADD_STAT(utilization, statistics::units::Ratio::get(), "Layer utilization")
{
occupancy
.flags(statistics::nozero);
utilization
.precision(1)
.flags(statistics::nozero);
utilization = occupancy / simTicks;
}
template <typename SrcType, typename DstType>
void BaseXBar::Layer<SrcType, DstType>::occupyLayer(Tick until)
{
// ensure the state is busy at this point, as the layer should
// transition from idle as soon as it has decided to forward the
// packet to prevent any follow-on calls to sendTiming seeing an
// unoccupied layer
assert(state == BUSY);
// until should never be 0 as express snoops never occupy the layer
assert(until != 0);
xbar.schedule(releaseEvent, until);
// account for the occupied ticks
occupancy += until - curTick();
DPRINTF(BaseXBar, "The crossbar layer is now busy from tick %d to %d\n",
curTick(), until);
}
template <typename SrcType, typename DstType>
bool
BaseXBar::Layer<SrcType, DstType>::tryTiming(SrcType* src_port)
{
// if we are in the retry state, we will not see anything but the
// retrying port (or in the case of the snoop ports the snoop
// response port that mirrors the actual CPU-side port) as we leave
// this state again in zero time if the peer does not immediately
// call the layer when receiving the retry
// first we see if the layer is busy, next we check if the
// destination port is already engaged in a transaction waiting
// for a retry from the peer
if (state == BUSY || waitingForPeer != NULL) {
// the port should not be waiting already
assert(std::find(waitingForLayer.begin(), waitingForLayer.end(),
src_port) == waitingForLayer.end());
// put the port at the end of the retry list waiting for the
// layer to be freed up (and in the case of a busy peer, for
// that transaction to go through, and then the layer to free
// up)
waitingForLayer.push_back(src_port);
return false;
}
state = BUSY;
return true;
}
template <typename SrcType, typename DstType>
void
BaseXBar::Layer<SrcType, DstType>::succeededTiming(Tick busy_time)
{
// we should have gone from idle or retry to busy in the tryTiming
// test
assert(state == BUSY);
// occupy the layer accordingly
occupyLayer(busy_time);
}
template <typename SrcType, typename DstType>
void
BaseXBar::Layer<SrcType, DstType>::failedTiming(SrcType* src_port,
Tick busy_time)
{
// ensure no one got in between and tried to send something to
// this port
assert(waitingForPeer == NULL);
// if the source port is the current retrying one or not, we have
// failed in forwarding and should track that we are now waiting
// for the peer to send a retry
waitingForPeer = src_port;
// we should have gone from idle or retry to busy in the tryTiming
// test
assert(state == BUSY);
// occupy the bus accordingly
occupyLayer(busy_time);
}
template <typename SrcType, typename DstType>
void
BaseXBar::Layer<SrcType, DstType>::releaseLayer()
{
// releasing the bus means we should now be idle
assert(state == BUSY);
assert(!releaseEvent.scheduled());
// update the state
state = IDLE;
// bus layer is now idle, so if someone is waiting we can retry
if (!waitingForLayer.empty()) {
// there is no point in sending a retry if someone is still
// waiting for the peer
if (waitingForPeer == NULL)
retryWaiting();
} else if (waitingForPeer == NULL && drainState() == DrainState::Draining) {
DPRINTF(Drain, "Crossbar done draining, signaling drain manager\n");
//If we weren't able to drain before, do it now.
signalDrainDone();
}
}
template <typename SrcType, typename DstType>
void
BaseXBar::Layer<SrcType, DstType>::retryWaiting()
{
// this should never be called with no one waiting
assert(!waitingForLayer.empty());
// we always go to retrying from idle
assert(state == IDLE);
// update the state
state = RETRY;
// set the retrying port to the front of the retry list and pop it
// off the list
SrcType* retryingPort = waitingForLayer.front();
waitingForLayer.pop_front();
// tell the port to retry, which in some cases ends up calling the
// layer again
sendRetry(retryingPort);
// If the layer is still in the retry state, sendTiming wasn't
// called in zero time (e.g. the cache does this when a writeback
// is squashed)
if (state == RETRY) {
// update the state to busy and reset the retrying port, we
// have done our bit and sent the retry
state = BUSY;
// occupy the crossbar layer until the next clock edge
occupyLayer(xbar.clockEdge());
}
}
template <typename SrcType, typename DstType>
void
BaseXBar::Layer<SrcType, DstType>::recvRetry()
{
// we should never get a retry without having failed to forward
// something to this port
assert(waitingForPeer != NULL);
// add the port where the failed packet originated to the front of
// the waiting ports for the layer, this allows us to call retry
// on the port immediately if the crossbar layer is idle
waitingForLayer.push_front(waitingForPeer);
// we are no longer waiting for the peer
waitingForPeer = NULL;
// if the layer is idle, retry this port straight away, if we
// are busy, then simply let the port wait for its turn
if (state == IDLE) {
retryWaiting();
} else {
assert(state == BUSY);
}
}
PortID
BaseXBar::findPort(AddrRange addr_range)
{
// we should never see any address lookups before we've got the
// ranges of all connected CPU-side-port modules
assert(gotAllAddrRanges);
// Check the address map interval tree
auto i = portMap.contains(addr_range);
if (i != portMap.end()) {
return i->second;
}
// Check if this matches the default range
if (useDefaultRange) {
if (addr_range.isSubset(defaultRange)) {
DPRINTF(AddrRanges, " found addr %s on default\n",
addr_range.to_string());
return defaultPortID;
}
} else if (defaultPortID != InvalidPortID) {
DPRINTF(AddrRanges, "Unable to find destination for %s, "
"will use default port\n", addr_range.to_string());
return defaultPortID;
}
// we should use the range for the default port and it did not
// match, or the default port is not set
fatal("Unable to find destination for %s on %s\n", addr_range.to_string(),
name());
}
/** Function called by the port when the crossbar is receiving a range change.*/
void
BaseXBar::recvRangeChange(PortID mem_side_port_id)
{
DPRINTF(AddrRanges, "Received range change from cpu_side_ports %s\n",
memSidePorts[mem_side_port_id]->getPeer());
// remember that we got a range from this memory-side port and thus the
// connected CPU-side-port module
gotAddrRanges[mem_side_port_id] = true;
// update the global flag
if (!gotAllAddrRanges) {
// take a logical AND of all the ports and see if we got
// ranges from everyone
gotAllAddrRanges = true;
std::vector<bool>::const_iterator r = gotAddrRanges.begin();
while (gotAllAddrRanges && r != gotAddrRanges.end()) {
gotAllAddrRanges &= *r++;
}
if (gotAllAddrRanges)
DPRINTF(AddrRanges, "Got address ranges from all responders\n");
}
// note that we could get the range from the default port at any
// point in time, and we cannot assume that the default range is
// set before the other ones are, so we do additional checks once
// all ranges are provided
if (mem_side_port_id == defaultPortID) {
// only update if we are indeed checking ranges for the
// default port since the port might not have a valid range
// otherwise
if (useDefaultRange) {
AddrRangeList ranges = memSidePorts[mem_side_port_id]->
getAddrRanges();
if (ranges.size() != 1)
fatal("Crossbar %s may only have a single default range",
name());
defaultRange = ranges.front();
}
} else {
// the ports are allowed to update their address ranges
// dynamically, so remove any existing entries
if (gotAddrRanges[mem_side_port_id]) {
for (auto p = portMap.begin(); p != portMap.end(); ) {
if (p->second == mem_side_port_id)
// erasing invalidates the iterator, so advance it
// before the deletion takes place
portMap.erase(p++);
else
p++;
}
}
AddrRangeList ranges = memSidePorts[mem_side_port_id]->
getAddrRanges();
for (const auto& r: ranges) {
DPRINTF(AddrRanges, "Adding range %s for id %d\n",
r.to_string(), mem_side_port_id);
if (portMap.insert(r, mem_side_port_id) == portMap.end()) {
PortID conflict_id = portMap.intersects(r)->second;
fatal("%s has two ports responding within range "
"%s:\n\t%s\n\t%s\n",
name(),
r.to_string(),
memSidePorts[mem_side_port_id]->getPeer(),
memSidePorts[conflict_id]->getPeer());
}
}
}
// if we have received ranges from all our neighbouring CPU-side-port
// modules, go ahead and tell our connected memory-side-port modules in
// turn, this effectively assumes a tree structure of the system
if (gotAllAddrRanges) {
DPRINTF(AddrRanges, "Aggregating address ranges\n");
xbarRanges.clear();
// start out with the default range
if (useDefaultRange) {
if (!gotAddrRanges[defaultPortID])
fatal("Crossbar %s uses default range, but none provided",
name());
xbarRanges.push_back(defaultRange);
DPRINTF(AddrRanges, "-- Adding default %s\n",
defaultRange.to_string());
}
// merge all interleaved ranges and add any range that is not
// a subset of the default range
std::vector<AddrRange> intlv_ranges;
for (const auto& r: portMap) {
// if the range is interleaved then save it for now
if (r.first.interleaved()) {
// if we already got interleaved ranges that are not
// part of the same range, then first do a merge
// before we add the new one
if (!intlv_ranges.empty() &&
!intlv_ranges.back().mergesWith(r.first)) {
DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
intlv_ranges.size());
AddrRange merged_range(intlv_ranges);
// next decide if we keep the merged range or not
if (!(useDefaultRange &&
merged_range.isSubset(defaultRange))) {
xbarRanges.push_back(merged_range);
DPRINTF(AddrRanges, "-- Adding merged range %s\n",
merged_range.to_string());
}
intlv_ranges.clear();
}
intlv_ranges.push_back(r.first);
} else {
// keep the current range if not a subset of the default
if (!(useDefaultRange &&
r.first.isSubset(defaultRange))) {
xbarRanges.push_back(r.first);
DPRINTF(AddrRanges, "-- Adding range %s\n",
r.first.to_string());
}
}
}
// if there is still interleaved ranges waiting to be merged,
// go ahead and do it
if (!intlv_ranges.empty()) {
DPRINTF(AddrRanges, "-- Merging range from %d ranges\n",
intlv_ranges.size());
AddrRange merged_range(intlv_ranges);
if (!(useDefaultRange && merged_range.isSubset(defaultRange))) {
xbarRanges.push_back(merged_range);
DPRINTF(AddrRanges, "-- Adding merged range %s\n",
merged_range.to_string());
}
}
// also check that no range partially intersects with the
// default range, this has to be done after all ranges are set
// as there are no guarantees for when the default range is
// update with respect to the other ones
if (useDefaultRange) {
for (const auto& r: xbarRanges) {
// see if the new range is partially
// overlapping the default range
if (r.intersects(defaultRange) &&
!r.isSubset(defaultRange))
fatal("Range %s intersects the " \
"default range of %s but is not a " \
"subset\n", r.to_string(), name());
}
}
// tell all our neighbouring memory-side ports that our address
// ranges have changed
for (const auto& port: cpuSidePorts)
port->sendRangeChange();
}
}
AddrRangeList
BaseXBar::getAddrRanges() const
{
// we should never be asked without first having sent a range
// change, and the latter is only done once we have all the ranges
// of the connected devices
assert(gotAllAddrRanges);
// at the moment, this never happens, as there are no cycles in
// the range queries and no devices on the memory side of a crossbar
// (CPU, cache, bridge etc) actually care about the ranges of the
// ports they are connected to
DPRINTF(AddrRanges, "Received address range request\n");
return xbarRanges;
}
void
BaseXBar::regStats()
{
ClockedObject::regStats();
using namespace statistics;
transDist
.init(MemCmd::NUM_MEM_CMDS)
.flags(nozero);
// get the string representation of the commands
for (int i = 0; i < MemCmd::NUM_MEM_CMDS; i++) {
MemCmd cmd(i);
const std::string &cstr = cmd.toString();
transDist.subname(i, cstr);
}
pktCount
.init(cpuSidePorts.size(), memSidePorts.size())
.flags(total | nozero | nonan);
pktSize
.init(cpuSidePorts.size(), memSidePorts.size())
.flags(total | nozero | nonan);
// both the packet count and total size are two-dimensional
// vectors, indexed by CPU-side port id and memory-side port id, thus the
// neighbouring memory-side ports and CPU-side ports, they do not
// differentiate what came from the memory-side ports and was forwarded to
// the CPU-side ports (requests and snoop responses) and what came from
// the CPU-side ports and was forwarded to the memory-side ports (responses
// and snoop requests)
for (int i = 0; i < cpuSidePorts.size(); i++) {
pktCount.subname(i, cpuSidePorts[i]->getPeer().name());
pktSize.subname(i, cpuSidePorts[i]->getPeer().name());
for (int j = 0; j < memSidePorts.size(); j++) {
pktCount.ysubname(j, memSidePorts[j]->getPeer().name());
pktSize.ysubname(j, memSidePorts[j]->getPeer().name());
}
}
}
template <typename SrcType, typename DstType>
DrainState
BaseXBar::Layer<SrcType, DstType>::drain()
{
//We should check that we're not "doing" anything, and that noone is
//waiting. We might be idle but have someone waiting if the device we
//contacted for a retry didn't actually retry.
if (state != IDLE) {
DPRINTF(Drain, "Crossbar not drained\n");
return DrainState::Draining;
} else {
return DrainState::Drained;
}
}
/**
* Crossbar layer template instantiations. Could be removed with _impl.hh
* file, but since there are only two given options (RequestPort and
* ResponsePort) it seems a bit excessive at this point.
*/
template class BaseXBar::Layer<ResponsePort, RequestPort>;
template class BaseXBar::Layer<RequestPort, ResponsePort>;
} // namespace gem5