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/*
* Copyright (c) 2014-2015 Advanced Micro Devices, Inc.
* All rights reserved.
*
* For use for simulation and test purposes only
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. Neither the name of the copyright holder 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 HOLDER 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.
*/
#include "gpu-compute/lds_state.hh"
#include <array>
#include <cstdio>
#include <cstdlib>
#include "gpu-compute/compute_unit.hh"
#include "gpu-compute/gpu_dyn_inst.hh"
#include "gpu-compute/shader.hh"
namespace gem5
{
/**
* the default constructor that works with SWIG
*/
LdsState::LdsState(const Params &params) :
ClockedObject(params),
tickEvent(this),
cuPort(name() + ".port", this),
maximumSize(params.size),
range(params.range),
bankConflictPenalty(params.bankConflictPenalty),
banks(params.banks)
{
fatal_if(params.banks <= 0,
"Number of LDS banks should be positive number");
fatal_if((params.banks & (params.banks - 1)) != 0,
"Number of LDS banks should be a power of 2");
fatal_if(params.size <= 0,
"cannot allocate an LDS with a size less than 1");
fatal_if(params.size % 2,
"the LDS should be an even number");
}
/**
* set the parent and name based on the parent
*/
void
LdsState::setParent(ComputeUnit *x_parent)
{
// check that this gets assigned to the same thing each time
fatal_if(!x_parent, "x_parent should not be nullptr");
fatal_if(x_parent == parent,
"should not be setting the parent twice");
parent = x_parent;
_name = x_parent->name() + ".LdsState";
}
/**
* derive the gpu mem packet from the packet and then count the bank conflicts
*/
unsigned
LdsState::countBankConflicts(PacketPtr packet, unsigned *bankAccesses)
{
Packet::SenderState *baseSenderState = packet->senderState;
while (baseSenderState->predecessor) {
baseSenderState = baseSenderState->predecessor;
}
const ComputeUnit::LDSPort::SenderState *senderState =
dynamic_cast<ComputeUnit::LDSPort::SenderState *>(baseSenderState);
fatal_if(!senderState,
"did not get the right sort of sender state");
GPUDynInstPtr gpuDynInst = senderState->getMemInst();
return countBankConflicts(gpuDynInst, bankAccesses);
}
// Count the total number of bank conflicts for the local memory packet
unsigned
LdsState::countBankConflicts(GPUDynInstPtr gpuDynInst,
unsigned *numBankAccesses)
{
int bank_conflicts = 0;
std::vector<int> bank;
// the number of LDS banks being touched by the memory instruction
int numBanks = std::min(parent->wfSize(), banks);
// if the wavefront size is larger than the number of LDS banks, we
// need to iterate over all work items to calculate the total
// number of bank conflicts
int groups = (parent->wfSize() > numBanks) ?
(parent->wfSize() / numBanks) : 1;
for (int i = 0; i < groups; i++) {
// Address Array holding all the work item addresses of an instruction
std::vector<Addr> addr_array;
addr_array.resize(numBanks, 0);
bank.clear();
bank.resize(banks, 0);
int max_bank = 0;
// populate the address array for all active work items
for (int j = 0; j < numBanks; j++) {
if (gpuDynInst->exec_mask[(i*numBanks)+j]) {
addr_array[j] = gpuDynInst->addr[(i*numBanks)+j];
} else {
addr_array[j] = std::numeric_limits<Addr>::max();
}
}
if (gpuDynInst->isLoad() || gpuDynInst->isStore()) {
// mask identical addresses
for (int j = 0; j < numBanks; ++j) {
for (int j0 = 0; j0 < j; j0++) {
if (addr_array[j] != std::numeric_limits<Addr>::max()
&& addr_array[j] == addr_array[j0]) {
addr_array[j] = std::numeric_limits<Addr>::max();
}
}
}
}
// calculate bank conflicts
for (int j = 0; j < numBanks; ++j) {
if (addr_array[j] != std::numeric_limits<Addr>::max()) {
int bankId = addr_array[j] % banks;
bank[bankId]++;
max_bank = std::max(max_bank, bank[bankId]);
// Count the number of LDS banks accessed.
// Since we have masked identical addresses all remaining
// accesses will need to be serialized if they access
// the same bank (bank conflict).
(*numBankAccesses)++;
}
}
bank_conflicts += max_bank;
}
panic_if(bank_conflicts > parent->wfSize(),
"Max bank conflicts should match num of work items per instr");
return bank_conflicts;
}
/**
* receive the packet from the CU
*/
bool
LdsState::CuSidePort::recvTimingReq(PacketPtr packet)
{
return ownerLds->processPacket(packet);
}
GPUDynInstPtr
LdsState::getDynInstr(PacketPtr packet)
{
ComputeUnit::LDSPort::SenderState *ss =
dynamic_cast<ComputeUnit::LDSPort::SenderState *>(
packet->senderState);
return ss->getMemInst();
}
/**
* process an incoming packet, add it to the return queue
*/
bool
LdsState::processPacket(PacketPtr packet)
{
unsigned bankAccesses = 0;
// the number of conflicts this packet will have when accessing the LDS
unsigned bankConflicts = countBankConflicts(packet, &bankAccesses);
// count the total number of physical LDS bank accessed
parent->stats.ldsBankAccesses += bankAccesses;
// count the LDS bank conflicts. A number set to 1 indicates one
// access per bank maximum so there are no bank conflicts
parent->stats.ldsBankConflictDist.sample(bankConflicts-1);
GPUDynInstPtr dynInst = getDynInstr(packet);
// account for the LDS bank conflict overhead
int busLength = (dynInst->isLoad()) ? parent->loadBusLength() :
(dynInst->isStore()) ? parent->storeBusLength() :
parent->loadBusLength();
// delay for accessing the LDS
Tick processingTime =
parent->cyclesToTicks(Cycles(bankConflicts * bankConflictPenalty)) +
parent->cyclesToTicks(Cycles(busLength));
// choose (delay + last packet in queue) or (now + delay) as the time to
// return this
Tick doneAt = earliestReturnTime() + processingTime;
// then store it for processing
return returnQueuePush(std::make_pair(doneAt, packet));
}
/**
* add this to the queue of packets to be returned
*/
bool
LdsState::returnQueuePush(std::pair<Tick, PacketPtr> thePair)
{
// TODO add time limits (e.g. one packet per cycle) and queue size limits
// and implement flow control
returnQueue.push(thePair);
// if there is no set wakeup time, look through the queue
if (!tickEvent.scheduled()) {
process();
}
return true;
}
/**
* receive a packet in functional mode
*/
void
LdsState::CuSidePort::recvFunctional(PacketPtr pkt)
{
fatal("not implemented");
}
/**
* receive a retry for a response
*/
void
LdsState::CuSidePort::recvRespRetry()
{
// TODO verify that this is the right way to do this
assert(ownerLds->isRetryResp());
ownerLds->setRetryResp(false);
ownerLds->process();
}
/**
* receive a retry
*/
void
LdsState::CuSidePort::recvRetry()
{
fatal("not implemented");
}
/**
* look for packets to return at this time
*/
bool
LdsState::process()
{
Tick now = clockEdge();
// send back completed packets
while (!returnQueue.empty() && returnQueue.front().first <= now) {
PacketPtr packet = returnQueue.front().second;
ComputeUnit::LDSPort::SenderState *ss =
dynamic_cast<ComputeUnit::LDSPort::SenderState *>(
packet->senderState);
GPUDynInstPtr gpuDynInst = ss->getMemInst();
gpuDynInst->initiateAcc(gpuDynInst);
packet->makeTimingResponse();
returnQueue.pop();
bool success = cuPort.sendTimingResp(packet);
if (!success) {
retryResp = true;
panic("have not handled timing responses being NACK'd when sent"
"back");
}
}
// determine the next wakeup time
if (!returnQueue.empty()) {
Tick next = returnQueue.front().first;
if (tickEvent.scheduled()) {
if (next < tickEvent.when()) {
tickEvent.deschedule();
tickEvent.schedule(next);
}
} else {
tickEvent.schedule(next);
}
}
return true;
}
/**
* wake up at this time and perform specified actions
*/
void
LdsState::TickEvent::process()
{
ldsState->process();
}
} // namespace gem5