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/*
* Copyright (c) 2011-2015 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/tlb_coalescer.hh"
#include <cstring>
#include "arch/x86/isa_traits.hh"
#include "base/logging.hh"
#include "debug/GPUTLB.hh"
#include "sim/process.hh"
TLBCoalescer::TLBCoalescer(const Params &p)
: ClockedObject(p),
TLBProbesPerCycle(p.probesPerCycle),
coalescingWindow(p.coalescingWindow),
disableCoalescing(p.disableCoalescing),
probeTLBEvent([this]{ processProbeTLBEvent(); },
"Probe the TLB below",
false, Event::CPU_Tick_Pri),
cleanupEvent([this]{ processCleanupEvent(); },
"Cleanup issuedTranslationsTable hashmap",
false, Event::Maximum_Pri),
stats(this)
{
// create the response ports based on the number of connected ports
for (size_t i = 0; i < p.port_cpu_side_ports_connection_count; ++i) {
cpuSidePort.push_back(new CpuSidePort(csprintf("%s-port%d", name(), i),
this, i));
}
// create the request ports based on the number of connected ports
for (size_t i = 0; i < p.port_mem_side_ports_connection_count; ++i) {
memSidePort.push_back(new MemSidePort(csprintf("%s-port%d", name(), i),
this, i));
}
}
Port &
TLBCoalescer::getPort(const std::string &if_name, PortID idx)
{
if (if_name == "cpu_side_ports") {
if (idx >= static_cast<PortID>(cpuSidePort.size())) {
panic("TLBCoalescer::getPort: unknown index %d\n", idx);
}
return *cpuSidePort[idx];
} else if (if_name == "mem_side_ports") {
if (idx >= static_cast<PortID>(memSidePort.size())) {
panic("TLBCoalescer::getPort: unknown index %d\n", idx);
}
return *memSidePort[idx];
} else {
panic("TLBCoalescer::getPort: unknown port %s\n", if_name);
}
}
/*
* This method returns true if the <incoming_pkt>
* can be coalesced with <coalesced_pkt> and false otherwise.
* A given set of rules is checked.
* The rules can potentially be modified based on the TLB level.
*/
bool
TLBCoalescer::canCoalesce(PacketPtr incoming_pkt, PacketPtr coalesced_pkt)
{
if (disableCoalescing)
return false;
TheISA::GpuTLB::TranslationState *incoming_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(incoming_pkt->senderState);
TheISA::GpuTLB::TranslationState *coalesced_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(coalesced_pkt->senderState);
// Rule 1: Coalesce requests only if they
// fall within the same virtual page
Addr incoming_virt_page_addr = roundDown(incoming_pkt->req->getVaddr(),
X86ISA::PageBytes);
Addr coalesced_virt_page_addr = roundDown(coalesced_pkt->req->getVaddr(),
X86ISA::PageBytes);
if (incoming_virt_page_addr != coalesced_virt_page_addr)
return false;
//* Rule 2: Coalesce requests only if they
// share a TLB Mode, i.e. they are both read
// or write requests.
BaseTLB::Mode incoming_mode = incoming_state->tlbMode;
BaseTLB::Mode coalesced_mode = coalesced_state->tlbMode;
if (incoming_mode != coalesced_mode)
return false;
// when we can coalesce a packet update the reqCnt
// that is the number of packets represented by
// this coalesced packet
if (!incoming_state->prefetch)
coalesced_state->reqCnt.back() += incoming_state->reqCnt.back();
return true;
}
/*
* We need to update the physical addresses of all the translation requests
* that were coalesced into the one that just returned.
*/
void
TLBCoalescer::updatePhysAddresses(PacketPtr pkt)
{
Addr virt_page_addr = roundDown(pkt->req->getVaddr(), X86ISA::PageBytes);
DPRINTF(GPUTLB, "Update phys. addr. for %d coalesced reqs for page %#x\n",
issuedTranslationsTable[virt_page_addr].size(), virt_page_addr);
TheISA::GpuTLB::TranslationState *sender_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(pkt->senderState);
TheISA::TlbEntry *tlb_entry = sender_state->tlbEntry;
assert(tlb_entry);
Addr first_entry_vaddr = tlb_entry->vaddr;
Addr first_entry_paddr = tlb_entry->paddr;
int page_size = tlb_entry->size();
bool uncacheable = tlb_entry->uncacheable;
int first_hit_level = sender_state->hitLevel;
// Get the physical page address of the translated request
// Using the page_size specified in the TLBEntry allows us
// to support different page sizes.
Addr phys_page_paddr = pkt->req->getPaddr();
phys_page_paddr &= ~(page_size - 1);
for (int i = 0; i < issuedTranslationsTable[virt_page_addr].size(); ++i) {
PacketPtr local_pkt = issuedTranslationsTable[virt_page_addr][i];
TheISA::GpuTLB::TranslationState *sender_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(
local_pkt->senderState);
// we are sending the packet back, so pop the reqCnt associated
// with this level in the TLB hiearchy
if (!sender_state->prefetch)
sender_state->reqCnt.pop_back();
/*
* Only the first packet from this coalesced request has been
* translated. Grab the translated phys. page addr and update the
* physical addresses of the remaining packets with the appropriate
* page offsets.
*/
if (i) {
Addr paddr = phys_page_paddr;
paddr |= (local_pkt->req->getVaddr() & (page_size - 1));
local_pkt->req->setPaddr(paddr);
if (uncacheable)
local_pkt->req->setFlags(Request::UNCACHEABLE);
// update senderState->tlbEntry, so we can insert
// the correct TLBEentry in the TLBs above.
auto p = sender_state->tc->getProcessPtr();
sender_state->tlbEntry =
new TheISA::TlbEntry(p->pid(), first_entry_vaddr,
first_entry_paddr, false, false);
// update the hitLevel for all uncoalesced reqs
// so that each packet knows where it hit
// (used for statistics in the CUs)
sender_state->hitLevel = first_hit_level;
}
ResponsePort *return_port = sender_state->ports.back();
sender_state->ports.pop_back();
// Translation is done - Convert to a response pkt if necessary and
// send the translation back
if (local_pkt->isRequest()) {
local_pkt->makeTimingResponse();
}
return_port->sendTimingResp(local_pkt);
}
// schedule clean up for end of this cycle
// This is a maximum priority event and must be on
// the same cycle as GPUTLB cleanup event to prevent
// race conditions with an IssueProbeEvent caused by
// MemSidePort::recvReqRetry
cleanupQueue.push(virt_page_addr);
if (!cleanupEvent.scheduled())
schedule(cleanupEvent, curTick());
}
// Receive translation requests, create a coalesced request,
// and send them to the TLB (TLBProbesPerCycle)
bool
TLBCoalescer::CpuSidePort::recvTimingReq(PacketPtr pkt)
{
// first packet of a coalesced request
PacketPtr first_packet = nullptr;
// true if we are able to do coalescing
bool didCoalesce = false;
// number of coalesced reqs for a given window
int coalescedReq_cnt = 0;
TheISA::GpuTLB::TranslationState *sender_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(pkt->senderState);
// push back the port to remember the path back
sender_state->ports.push_back(this);
bool update_stats = !sender_state->prefetch;
if (update_stats) {
// if reqCnt is empty then this packet does not represent
// multiple uncoalesced reqs(pkts) but just a single pkt.
// If it does though then the reqCnt for each level in the
// hierarchy accumulates the total number of reqs this packet
// represents
int req_cnt = 1;
if (!sender_state->reqCnt.empty())
req_cnt = sender_state->reqCnt.back();
sender_state->reqCnt.push_back(req_cnt);
// update statistics
coalescer->stats.uncoalescedAccesses++;
req_cnt = sender_state->reqCnt.back();
DPRINTF(GPUTLB, "receiving pkt w/ req_cnt %d\n", req_cnt);
coalescer->stats.queuingCycles -= (curTick() * req_cnt);
coalescer->stats.localqueuingCycles -= curTick();
}
// FIXME if you want to coalesce not based on the issueTime
// of the packets (i.e., from the compute unit's perspective)
// but based on when they reached this coalescer then
// remove the following if statement and use curTick() or
// coalescingWindow for the tick_index.
if (!sender_state->issueTime)
sender_state->issueTime = curTick();
// The tick index is used as a key to the coalescerFIFO hashmap.
// It is shared by all candidates that fall within the
// given coalescingWindow.
int64_t tick_index = sender_state->issueTime / coalescer->coalescingWindow;
if (coalescer->coalescerFIFO.count(tick_index)) {
coalescedReq_cnt = coalescer->coalescerFIFO[tick_index].size();
}
// see if we can coalesce the incoming pkt with another
// coalesced request with the same tick_index
for (int i = 0; i < coalescedReq_cnt; ++i) {
first_packet = coalescer->coalescerFIFO[tick_index][i][0];
if (coalescer->canCoalesce(pkt, first_packet)) {
coalescer->coalescerFIFO[tick_index][i].push_back(pkt);
DPRINTF(GPUTLB, "Coalesced req %i w/ tick_index %d has %d reqs\n",
i, tick_index,
coalescer->coalescerFIFO[tick_index][i].size());
didCoalesce = true;
break;
}
}
// if this is the first request for this tick_index
// or we did not manage to coalesce, update stats
// and make necessary allocations.
if (!coalescedReq_cnt || !didCoalesce) {
if (update_stats)
coalescer->stats.coalescedAccesses++;
std::vector<PacketPtr> new_array;
new_array.push_back(pkt);
coalescer->coalescerFIFO[tick_index].push_back(new_array);
DPRINTF(GPUTLB, "coalescerFIFO[%d] now has %d coalesced reqs after "
"push\n", tick_index,
coalescer->coalescerFIFO[tick_index].size());
}
//schedule probeTLBEvent next cycle to send the
//coalesced requests to the TLB
if (!coalescer->probeTLBEvent.scheduled()) {
coalescer->schedule(coalescer->probeTLBEvent,
curTick() + coalescer->clockPeriod());
}
return true;
}
void
TLBCoalescer::CpuSidePort::recvReqRetry()
{
panic("recvReqRetry called");
}
void
TLBCoalescer::CpuSidePort::recvFunctional(PacketPtr pkt)
{
TheISA::GpuTLB::TranslationState *sender_state =
safe_cast<TheISA::GpuTLB::TranslationState*>(pkt->senderState);
bool update_stats = !sender_state->prefetch;
if (update_stats)
coalescer->stats.uncoalescedAccesses++;
// If there is a pending timing request for this virtual address
// print a warning message. This is a temporary caveat of
// the current simulator where atomic and timing requests can
// coexist. FIXME remove this check/warning in the future.
Addr virt_page_addr = roundDown(pkt->req->getVaddr(), X86ISA::PageBytes);
int map_count = coalescer->issuedTranslationsTable.count(virt_page_addr);
if (map_count) {
DPRINTF(GPUTLB, "Warning! Functional access to addr %#x sees timing "
"req. pending\n", virt_page_addr);
}
coalescer->memSidePort[0]->sendFunctional(pkt);
}
AddrRangeList
TLBCoalescer::CpuSidePort::getAddrRanges() const
{
// currently not checked by the requestor
AddrRangeList ranges;
return ranges;
}
bool
TLBCoalescer::MemSidePort::recvTimingResp(PacketPtr pkt)
{
// a translation completed and returned
coalescer->updatePhysAddresses(pkt);
return true;
}
void
TLBCoalescer::MemSidePort::recvReqRetry()
{
//we've receeived a retry. Schedule a probeTLBEvent
if (!coalescer->probeTLBEvent.scheduled())
coalescer->schedule(coalescer->probeTLBEvent,
curTick() + coalescer->clockPeriod());
}
void
TLBCoalescer::MemSidePort::recvFunctional(PacketPtr pkt)
{
fatal("Memory side recvFunctional() not implemented in TLB coalescer.\n");
}
/*
* Here we scan the coalescer FIFO and issue the max
* number of permitted probes to the TLB below. We
* permit bypassing of coalesced requests for the same
* tick_index.
*
* We do not access the next tick_index unless we've
* drained the previous one. The coalesced requests
* that are successfully sent are moved to the
* issuedTranslationsTable table (the table which keeps
* track of the outstanding reqs)
*/
void
TLBCoalescer::processProbeTLBEvent()
{
// number of TLB probes sent so far
int sent_probes = 0;
// rejected denotes a blocking event
bool rejected = false;
// It is set to true either when the recvTiming of the TLB below
// returns false or when there is another outstanding request for the
// same virt. page.
DPRINTF(GPUTLB, "triggered TLBCoalescer %s\n", __func__);
for (auto iter = coalescerFIFO.begin();
iter != coalescerFIFO.end() && !rejected; ) {
int coalescedReq_cnt = iter->second.size();
int i = 0;
int vector_index = 0;
DPRINTF(GPUTLB, "coalescedReq_cnt is %d for tick_index %d\n",
coalescedReq_cnt, iter->first);
while (i < coalescedReq_cnt) {
++i;
PacketPtr first_packet = iter->second[vector_index][0];
// compute virtual page address for this request
Addr virt_page_addr = roundDown(first_packet->req->getVaddr(),
X86ISA::PageBytes);
// is there another outstanding request for the same page addr?
int pending_reqs =
issuedTranslationsTable.count(virt_page_addr);
if (pending_reqs) {
DPRINTF(GPUTLB, "Cannot issue - There are pending reqs for "
"page %#x\n", virt_page_addr);
++vector_index;
rejected = true;
continue;
}
// send the coalesced request for virt_page_addr
if (!memSidePort[0]->sendTimingReq(first_packet)) {
DPRINTF(GPUTLB, "Failed to send TLB request for page %#x\n",
virt_page_addr);
// No need for a retries queue since we are already buffering
// the coalesced request in coalescerFIFO.
rejected = true;
++vector_index;
} else {
TheISA::GpuTLB::TranslationState *tmp_sender_state =
safe_cast<TheISA::GpuTLB::TranslationState*>
(first_packet->senderState);
bool update_stats = !tmp_sender_state->prefetch;
if (update_stats) {
// req_cnt is total number of packets represented
// by the one we just sent counting all the way from
// the top of TLB hiearchy (i.e., from the CU)
int req_cnt = tmp_sender_state->reqCnt.back();
stats.queuingCycles += (curTick() * req_cnt);
DPRINTF(GPUTLB, "%s sending pkt w/ req_cnt %d\n",
name(), req_cnt);
// pkt_cnt is number of packets we coalesced into the one
// we just sent but only at this coalescer level
int pkt_cnt = iter->second[vector_index].size();
stats.localqueuingCycles += (curTick() * pkt_cnt);
}
DPRINTF(GPUTLB, "Successfully sent TLB request for page %#x",
virt_page_addr);
//copy coalescedReq to issuedTranslationsTable
issuedTranslationsTable[virt_page_addr]
= iter->second[vector_index];
//erase the entry of this coalesced req
iter->second.erase(iter->second.begin() + vector_index);
if (iter->second.empty())
assert(i == coalescedReq_cnt);
sent_probes++;
if (sent_probes == TLBProbesPerCycle)
return;
}
}
//if there are no more coalesced reqs for this tick_index
//erase the hash_map with the first iterator
if (iter->second.empty()) {
coalescerFIFO.erase(iter++);
} else {
++iter;
}
}
}
void
TLBCoalescer::processCleanupEvent()
{
while (!cleanupQueue.empty()) {
Addr cleanup_addr = cleanupQueue.front();
cleanupQueue.pop();
issuedTranslationsTable.erase(cleanup_addr);
DPRINTF(GPUTLB, "Cleanup - Delete coalescer entry with key %#x\n",
cleanup_addr);
}
}
TLBCoalescer::TLBCoalescerStats::TLBCoalescerStats(Stats::Group *parent)
: Stats::Group(parent),
ADD_STAT(uncoalescedAccesses, "Number of uncoalesced TLB accesses"),
ADD_STAT(coalescedAccesses, "Number of coalesced TLB accesses"),
ADD_STAT(queuingCycles, "Number of cycles spent in queue"),
ADD_STAT(localqueuingCycles,
"Number of cycles spent in queue for all incoming reqs"),
ADD_STAT(localLatency, "Avg. latency over all incoming pkts")
{
localLatency = localqueuingCycles / uncoalescedAccesses;
}