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gpu-compute,mem-ruby: Properly create/handle WriteCompletePkts

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There is a flow of packets as so:
WriteResp -> WriteReq -> WriteCompleteResp

These packets share some variables, in particular senderState and a
status vector.

One issue was the WriteResp packet decremented the status vector, which
was used by the WriteCompleteResp packets to determine when to handle
the global memory response. This could lead to multiple
WriteCompleteResp packets attempting to handle the global memory
response.

Because of that, the WriteCompleteResp packets needed to handle the
status vector. this patch moves WriteCompleteResp packet handling back
into ComputeUnit::DataPort::processMemRespEvent from
ComputeUnit::DataPort::recvTimingResp. This helps remove some redundant
code.

This patch has the WriteResp packet return without doing any status
vector handling, and without deleting the senderState, which had
previously caused a segfault.

Another issue was WriteCompleteResp packets weren't being issued for
each active lane, as the coalesced request was being issued too early.
In order to fix that, we have to ensure every active lane puts their
request into their applicable coalesced request before issuing the
coalesced request. Because of that change, we change the issuing of
CoalescedRequests from GPUCoalescer::coalescePacket to
GPUCoalescer::completeIssue.

That change involves adding a new variable to store the
CoalescedRequests that are created in the calls to coalescePacket. This
variable is a map from instruction sequence number to coalesced
requests.

Additionally, the WriteCompleteResp packet was attempting to access
physical memory in hitCallback while not having any data, which
caused a crash. This can be resolved either by not allowing
WriteCompleteResp packets to access memory, or by copying the data
from the WriteReq packet. This patch denies WriteCompleteResp packets
memory access in hitCallback.

Finally, in VIPERCoalescer::writeCompleteCallback there was a map
that held the WriteComplete packets, but no packets were ever being
removed. This patch removes packets that match the address that was
passed in to the function.

Change-Id: I9a064a0def2bf6c513f5295596c56b1b652b0ca4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33656
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Kyle Roarty
2020-08-28 17:42:10 -05:00
parent 41958f4afe
commit b20cc7e6d8
5 changed files with 57 additions and 56 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
src/gpu-compute/compute_unit.cc
View File

@@ -862,33 +862,6 @@ ComputeUnit::DataPort::recvTimingResp(PacketPtr pkt)
delete pkt->senderState;
delete pkt;
return true;
} else if (pkt->cmd == MemCmd::WriteCompleteResp) {
// this is for writeComplete callback
// we simply get decrement write-related wait counters
assert(gpuDynInst);
M5_VAR_USED Wavefront *w =
computeUnit->wfList[gpuDynInst->simdId][gpuDynInst->wfSlotId];
assert(w);
DPRINTF(GPUExec, "WriteCompleteResp: WF[%d][%d] WV%d %s decrementing "
"outstanding reqs %d => %d\n", gpuDynInst->simdId,
gpuDynInst->wfSlotId, gpuDynInst->wfDynId,
gpuDynInst->disassemble(), w->outstandingReqs,
w->outstandingReqs - 1);
if (gpuDynInst->allLanesZero()) {
// ask gm pipe to decrement request counters, instead of directly
// performing here, to avoid asynchronous counter update and
// instruction retirement (which may hurt waincnt effects)
computeUnit->globalMemoryPipe.handleResponse(gpuDynInst);
DPRINTF(GPUMem, "CU%d: WF[%d][%d]: write totally complete\n",
computeUnit->cu_id, gpuDynInst->simdId,
gpuDynInst->wfSlotId);
}
delete pkt->senderState;
delete pkt;
return true;
}
@@ -1319,10 +1292,16 @@ ComputeUnit::DataPort::processMemRespEvent(PacketPtr pkt)
Addr paddr = pkt->req->getPaddr();
// mem sync resp and write-complete callback must be handled already in
// mem sync resp callback must be handled already in
// DataPort::recvTimingResp
assert(pkt->cmd != MemCmd::MemSyncResp);
assert(pkt->cmd != MemCmd::WriteCompleteResp);
// The status vector and global memory response for WriteResp packets get
// handled by the WriteCompleteResp packets.
if (pkt->cmd == MemCmd::WriteResp) {
delete pkt;
return;
}
// this is for read, write and atomic
int index = gpuDynInst->memStatusVector[paddr].back();
@@ -1356,17 +1335,13 @@ ComputeUnit::DataPort::processMemRespEvent(PacketPtr pkt)
gpuDynInst->memStatusVector.clear();
// note: only handle read response here; for write, the response
// is separately handled when writeComplete callback is received
if (pkt->isRead()) {
gpuDynInst->
profileRoundTripTime(curTick(), InstMemoryHop::GMEnqueue);
compute_unit->globalMemoryPipe.handleResponse(gpuDynInst);
gpuDynInst->
profileRoundTripTime(curTick(), InstMemoryHop::GMEnqueue);
compute_unit->globalMemoryPipe.handleResponse(gpuDynInst);
DPRINTF(GPUMem, "CU%d: WF[%d][%d]: packet totally complete\n",
compute_unit->cu_id, gpuDynInst->simdId,
gpuDynInst->wfSlotId);
}
DPRINTF(GPUMem, "CU%d: WF[%d][%d]: packet totally complete\n",
compute_unit->cu_id, gpuDynInst->simdId,
gpuDynInst->wfSlotId);
} else {
if (pkt->isRead()) {
if (!compute_unit->headTailMap.count(gpuDynInst)) {

20
src/mem/ruby/system/GPUCoalescer.cc
View File

@@ -682,10 +682,11 @@ GPUCoalescer::coalescePacket(PacketPtr pkt)
// create a new coalecsed request and issue it immediately.
auto reqList = std::deque<CoalescedRequest*> { creq };
coalescedTable.insert(std::make_pair(line_addr, reqList));
DPRINTF(GPUCoalescer, "Issued req type %s seqNum %d\n",
RubyRequestType_to_string(creq->getRubyType()), seqNum);
issueRequest(creq);
if (!coalescedReqs.count(seqNum)) {
coalescedReqs.insert(std::make_pair(seqNum, reqList));
} else {
coalescedReqs.at(seqNum).push_back(creq);
}
} else {
// The request is for a line address that is already outstanding
// but for a different instruction. Add it as a new request to be
@@ -773,6 +774,17 @@ GPUCoalescer::completeIssue()
[&](PacketPtr pkt) { return coalescePacket(pkt); }
);
if (coalescedReqs.count(seq_num)) {
auto& creqs = coalescedReqs.at(seq_num);
for (auto creq : creqs) {
DPRINTF(GPUCoalescer, "Issued req type %s seqNum %d\n",
RubyRequestType_to_string(creq->getRubyType()),
seq_num);
issueRequest(creq);
}
coalescedReqs.erase(seq_num);
}
assert(pkt_list_size >= pkt_list->size());
size_t pkt_list_diff = pkt_list_size - pkt_list->size();

4
src/mem/ruby/system/GPUCoalescer.hh
View File

@@ -430,6 +430,10 @@ class GPUCoalescer : public RubyPort
// (typically the number of blocks in TCP). If there are duplicates of
// an address, the are serviced in age order.
std::map<Addr, std::deque<CoalescedRequest*>> coalescedTable;
// Map of instruction sequence number to coalesced requests that get
// created in coalescePacket, used in completeIssue to send the fully
// coalesced request
std::unordered_map<uint64_t, std::deque<CoalescedRequest*>> coalescedReqs;
// a map btw an instruction sequence number and PendingWriteInst
// this is used to do a final call back for each write when it is

3
src/mem/ruby/system/RubyPort.cc
View File

@@ -546,7 +546,8 @@ RubyPort::MemResponsePort::hitCallback(PacketPtr pkt)
}
// Flush, acquire, release requests don't access physical memory
if (pkt->isFlush() || pkt->cmd == MemCmd::MemSyncReq) {
if (pkt->isFlush() || pkt->cmd == MemCmd::MemSyncReq
|| pkt->cmd == MemCmd::WriteCompleteResp) {
accessPhysMem = false;
}

33
src/mem/ruby/system/VIPERCoalescer.cc
View File

@@ -238,19 +238,28 @@ VIPERCoalescer::writeCompleteCallback(Addr addr, uint64_t instSeqNum)
assert(m_writeCompletePktMap.count(key) == 1 &&
!m_writeCompletePktMap[key].empty());
for (auto writeCompletePkt : m_writeCompletePktMap[key]) {
if (makeLineAddress(writeCompletePkt->getAddr()) == addr) {
RubyPort::SenderState *ss =
safe_cast<RubyPort::SenderState *>
(writeCompletePkt->senderState);
MemResponsePort *port = ss->port;
assert(port != NULL);
m_writeCompletePktMap[key].erase(
std::remove_if(
m_writeCompletePktMap[key].begin(),
m_writeCompletePktMap[key].end(),
[addr](PacketPtr writeCompletePkt) -> bool {
if (makeLineAddress(writeCompletePkt->getAddr()) == addr) {
RubyPort::SenderState *ss =
safe_cast<RubyPort::SenderState *>
(writeCompletePkt->senderState);
MemResponsePort *port = ss->port;
assert(port != NULL);
writeCompletePkt->senderState = ss->predecessor;
delete ss;
port->hitCallback(writeCompletePkt);
}
}
writeCompletePkt->senderState = ss->predecessor;
delete ss;
port->hitCallback(writeCompletePkt);
return true;
}
return false;
}
),
m_writeCompletePktMap[key].end()
);
trySendRetries();