changeset 33b4ea05c261 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=33b4ea05c261
description:
mem: Tie in the snoop filter in the coherent bus
diffstat:
src/mem/Bus.py | 1 +
src/mem/coherent_bus.cc | 181 +++++++++++++++++++++++++++++++++++++++--------
src/mem/coherent_bus.hh | 43 ++++++++++-
3 files changed, 191 insertions(+), 34 deletions(-)
diffs (truncated from 387 to 300 lines):
diff -r 3ab6c2a5a407 -r 33b4ea05c261 src/mem/Bus.py
--- a/src/mem/Bus.py Thu Apr 24 13:28:47 2014 +0100
+++ b/src/mem/Bus.py Sat Sep 20 17:18:29 2014 -0400
@@ -75,6 +75,7 @@
cxx_header = "mem/coherent_bus.hh"
system = Param.System(Parent.any, "System that the bus belongs to.")
+ snoop_filter = Param.SnoopFilter(NULL, "Selected snoop filter for the
bus.")
class SnoopFilter(SimObject):
type = 'SnoopFilter'
diff -r 3ab6c2a5a407 -r 33b4ea05c261 src/mem/coherent_bus.cc
--- a/src/mem/coherent_bus.cc Thu Apr 24 13:28:47 2014 +0100
+++ b/src/mem/coherent_bus.cc Sat Sep 20 17:18:29 2014 -0400
@@ -55,7 +55,7 @@
#include "sim/system.hh"
CoherentBus::CoherentBus(const CoherentBusParams *p)
- : BaseBus(p), system(p->system)
+ : BaseBus(p), system(p->system), snoopFilter(p->snoop_filter)
{
// create the ports based on the size of the master and slave
// vector ports, and the presence of the default port, the ports
@@ -95,6 +95,9 @@
snoopRespPorts.push_back(new SnoopRespPort(*bp, *this));
}
+ if (snoopFilter)
+ snoopFilter->setSlavePorts(slavePorts);
+
clearPortCache();
}
@@ -171,7 +174,18 @@
if (!pkt->req->isUncacheable() && !system->bypassCaches()) {
// the packet is a memory-mapped request and should be
// broadcasted to our snoopers but the source
- forwardTiming(pkt, slave_port_id);
+ if (snoopFilter) {
+ // check with the snoop filter where to forward this packet
+ auto sf_res = snoopFilter->lookupRequest(pkt, *src_port);
+ packetFinishTime += sf_res.second * clockPeriod();
+ DPRINTF(CoherentBus, "recvTimingReq: src %s %s 0x%x"\
+ " SF size: %i lat: %i\n", src_port->name(),
+ pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),
+ sf_res.second);
+ forwardTiming(pkt, slave_port_id, sf_res.first);
+ } else {
+ forwardTiming(pkt, slave_port_id);
+ }
}
// remember if we add an outstanding req so we can undo it if
@@ -190,9 +204,27 @@
outstandingReq.insert(pkt->req);
}
+ // Note: Cannot create a copy of the full packet, here.
+ MemCmd orig_cmd(pkt->cmd);
+
// since it is a normal request, attempt to send the packet
bool success = masterPorts[master_port_id]->sendTimingReq(pkt);
+ if (snoopFilter && !pkt->req->isUncacheable()
+ && !system->bypassCaches()) {
+ // The packet may already be overwritten by the sendTimingReq function.
+ // The snoop filter needs to see the original request *and* the return
+ // status of the send operation, so we need to recreate the original
+ // request. Atomic mode does not have the issue, as there the send
+ // operation and the response happen instantaneously and don't need two
+ // phase tracking.
+ MemCmd tmp_cmd(pkt->cmd);
+ pkt->cmd = orig_cmd;
+ // Let the snoop filter know about the success of the send operation
+ snoopFilter->updateRequest(pkt, *src_port, !success);
+ pkt->cmd = tmp_cmd;
+ }
+
// if this is an express snoop, we are done at this point
if (is_express_snoop) {
assert(success);
@@ -267,6 +299,11 @@
// have seen passing through the bus
assert(outstandingReq.find(pkt->req) != outstandingReq.end());
+ if (snoopFilter && !pkt->req->isUncacheable() && !system->bypassCaches()) {
+ // let the snoop filter inspect the response and update its state
+ snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]);
+ }
+
// remove it as outstanding
outstandingReq.erase(pkt->req);
@@ -306,8 +343,20 @@
// set the source port for routing of the response
pkt->setSrc(master_port_id);
- // forward to all snoopers
- forwardTiming(pkt, InvalidPortID);
+ if (snoopFilter) {
+ // let the Snoop Filter work its magic and guide probing
+ auto sf_res = snoopFilter->lookupSnoop(pkt);
+ // No timing here: packetFinishTime += sf_res.second * clockPeriod();
+ DPRINTF(CoherentBus, "recvTimingSnoopReq: src %s %s 0x%x"\
+ " SF size: %i lat: %i\n", masterPorts[master_port_id]->name(),
+ pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),
+ sf_res.second);
+
+ // forward to all snoopers
+ forwardTiming(pkt, InvalidPortID, sf_res.first);
+ } else {
+ forwardTiming(pkt, InvalidPortID);
+ }
// a snoop request came from a connected slave device (one of
// our master ports), and if it is not coming from the slave
@@ -372,6 +421,13 @@
// this is a snoop response to a snoop request we forwarded,
// e.g. coming from the L1 and going to the L2, and it should
// be forwarded as a snoop response
+
+ if (snoopFilter) {
+ // update the probe filter so that it can properly track the line
+ snoopFilter->updateSnoopForward(pkt, *slavePorts[slave_port_id],
+ *masterPorts[dest_port_id]);
+ }
+
bool success M5_VAR_USED =
masterPorts[dest_port_id]->sendTimingSnoopResp(pkt);
pktCount[slave_port_id][dest_port_id]++;
@@ -393,6 +449,16 @@
// original request came from
assert(slave_port_id != dest_port_id);
+ if (snoopFilter) {
+ // update the probe filter so that it can properly track the line
+ snoopFilter->updateSnoopResponse(pkt, *slavePorts[slave_port_id],
+ *slavePorts[dest_port_id]);
+ }
+
+ DPRINTF(CoherentBus, "recvTimingSnoopResp: src %s %s 0x%x"\
+ " FWD RESP\n", src_port->name(), pkt->cmdString(),
+ pkt->getAddr());
+
// as a normal response, it should go back to a master through
// one of our slave ports, at this point we are ignoring the
// fact that the response layer could be busy and do not touch
@@ -420,7 +486,8 @@
void
-CoherentBus::forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id)
+CoherentBus::forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
+ const std::vector<SlavePort*>& dests)
{
DPRINTF(CoherentBus, "%s for %s address %x size %d\n", __func__,
pkt->cmdString(), pkt->getAddr(), pkt->getSize());
@@ -430,7 +497,7 @@
unsigned fanout = 0;
- for (SlavePortIter s = snoopPorts.begin(); s != snoopPorts.end(); ++s) {
+ for (SlavePortConstIter s = dests.begin(); s != dests.end(); ++s) {
SlavePort *p = *s;
// we could have gotten this request from a snooping master
// (corresponding to our own slave port that is also in
@@ -473,10 +540,23 @@
// uncacheable requests need never be snooped
if (!pkt->req->isUncacheable() && !system->bypassCaches()) {
// forward to all snoopers but the source
- std::pair<MemCmd, Tick> snoop_result =
- forwardAtomic(pkt, slave_port_id);
+ std::pair<MemCmd, Tick> snoop_result;
+ if (snoopFilter) {
+ // check with the snoop filter where to forward this packet
+ auto sf_res =
+ snoopFilter->lookupRequest(pkt, *slavePorts[slave_port_id]);
+ snoop_response_latency += sf_res.second * clockPeriod();
+ DPRINTF(CoherentBus, "%s: src %s %s 0x%x"\
+ " SF size: %i lat: %i\n", __func__,
+ slavePorts[slave_port_id]->name(), pkt->cmdString(),
+ pkt->getAddr(), sf_res.first.size(), sf_res.second);
+ snoop_result = forwardAtomic(pkt, slave_port_id, InvalidPortID,
+ sf_res.first);
+ } else {
+ snoop_result = forwardAtomic(pkt, slave_port_id);
+ }
snoop_response_cmd = snoop_result.first;
- snoop_response_latency = snoop_result.second;
+ snoop_response_latency += snoop_result.second;
}
// even if we had a snoop response, we must continue and also
@@ -486,6 +566,12 @@
// forward the request to the appropriate destination
Tick response_latency = masterPorts[dest_id]->sendAtomic(pkt);
+ // Lower levels have replied, tell the snoop filter
+ if (snoopFilter && !pkt->req->isUncacheable() && !system->bypassCaches() &&
+ pkt->isResponse()) {
+ snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]);
+ }
+
// if we got a response from a snooper, restore it here
if (snoop_response_cmd != MemCmd::InvalidCmd) {
// no one else should have responded
@@ -515,10 +601,21 @@
snoopsThroughBus++;
// forward to all snoopers
- std::pair<MemCmd, Tick> snoop_result =
- forwardAtomic(pkt, InvalidPortID);
+ std::pair<MemCmd, Tick> snoop_result;
+ Tick snoop_response_latency = 0;
+ if (snoopFilter) {
+ auto sf_res = snoopFilter->lookupSnoop(pkt);
+ snoop_response_latency += sf_res.second * clockPeriod();
+ DPRINTF(CoherentBus, "%s: src %s %s 0x%x SF size: %i lat: %i\n",
+ __func__, masterPorts[master_port_id]->name(),
pkt->cmdString(),
+ pkt->getAddr(), sf_res.first.size(), sf_res.second);
+ snoop_result = forwardAtomic(pkt, InvalidPortID, master_port_id,
+ sf_res.first);
+ } else {
+ snoop_result = forwardAtomic(pkt, InvalidPortID);
+ }
MemCmd snoop_response_cmd = snoop_result.first;
- Tick snoop_response_latency = snoop_result.second;
+ snoop_response_latency += snoop_result.second;
if (snoop_response_cmd != MemCmd::InvalidCmd)
pkt->cmd = snoop_response_cmd;
@@ -535,7 +632,9 @@
}
std::pair<MemCmd, Tick>
-CoherentBus::forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id)
+CoherentBus::forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id,
+ PortID source_master_port_id,
+ const std::vector<SlavePort*>& dests)
{
// the packet may be changed on snoops, record the original
// command to enable us to restore it between snoops so that
@@ -549,33 +648,51 @@
unsigned fanout = 0;
- for (SlavePortIter s = snoopPorts.begin(); s != snoopPorts.end(); ++s) {
+ for (SlavePortConstIter s = dests.begin(); s != dests.end(); ++s) {
SlavePort *p = *s;
// we could have gotten this request from a snooping master
// (corresponding to our own slave port that is also in
// snoopPorts) and should not send it back to where it came
// from
- if (exclude_slave_port_id == InvalidPortID ||
- p->getId() != exclude_slave_port_id) {
- Tick latency = p->sendAtomicSnoop(pkt);
- fanout++;
+ if (exclude_slave_port_id != InvalidPortID &&
+ p->getId() == exclude_slave_port_id)
+ continue;
- // in contrast to a functional access, we have to keep on
- // going as all snoopers must be updated even if we get a
- // response
- if (pkt->isResponse()) {
- // response from snoop agent
- assert(pkt->cmd != orig_cmd);
- assert(pkt->memInhibitAsserted());
- // should only happen once
- assert(snoop_response_cmd == MemCmd::InvalidCmd);
- // save response state
- snoop_response_cmd = pkt->cmd;
- snoop_response_latency = latency;
- // restore original packet state for remaining snoopers
- pkt->cmd = orig_cmd;
+ Tick latency = p->sendAtomicSnoop(pkt);
+ fanout++;
+
+ // in contrast to a functional access, we have to keep on
+ // going as all snoopers must be updated even if we get a
+ // response
+ if (!pkt->isResponse())
+ continue;
+
+ // response from snoop agent
+ assert(pkt->cmd != orig_cmd);
+ assert(pkt->memInhibitAsserted());
+ // should only happen once
+ assert(snoop_response_cmd == MemCmd::InvalidCmd);
+ // save response state
+ snoop_response_cmd = pkt->cmd;
+ snoop_response_latency = latency;
+
+ if (snoopFilter) {
+ // Handle responses by the snoopers and differentiate between
+ // responses to requests from above and snoops from below
+ if (source_master_port_id != InvalidPortID) {
+ // Getting a response for a snoop from below
+ assert(exclude_slave_port_id == InvalidPortID);
+ snoopFilter->updateSnoopForward(pkt, *p,
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