SchedulerStatistics.cpp

//===--------------------- SchedulerStatistics.cpp --------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file implements the SchedulerStatistics interface.
///
//===----------------------------------------------------------------------===//

#include "Views/SchedulerStatistics.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/FormattedStream.h"

namespace llvm {
namespace mca {

SchedulerStatistics::SchedulerStatistics(const llvm::MCSubtargetInfo &STI)
    : SM(STI.getSchedModel()), LQResourceID(0), SQResourceID(0), NumIssued(0),
      NumCycles(0), MostRecentLoadDispatched(~0U),
      MostRecentStoreDispatched(~0U),
      Usage(STI.getSchedModel().NumProcResourceKinds, {0, 0, 0}) {
  if (SM.hasExtraProcessorInfo()) {
    const MCExtraProcessorInfo &EPI = SM.getExtraProcessorInfo();
    LQResourceID = EPI.LoadQueueID;
    SQResourceID = EPI.StoreQueueID;
  }
}

// FIXME: This implementation works under the assumption that load/store queue
// entries are reserved at 'instruction dispatched' stage, and released at
// 'instruction executed' stage. This currently matches the behavior of LSUnit.
//
// The current design minimizes the number of events generated by the
// Dispatch/Execute stages, at the cost of doing extra bookkeeping in method
// `onEvent`. However, it introduces a subtle dependency between this view and
// how the LSUnit works.
//
// In future we should add a new "memory queue" event type, so that we stop
// making assumptions on how LSUnit internally works (See PR39828).
void SchedulerStatistics::onEvent(const HWInstructionEvent &Event) {
  if (Event.Type == HWInstructionEvent::Issued) {
    const Instruction &Inst = *Event.IR.getInstruction();
    NumIssued += Inst.getDesc().NumMicroOps;
  } else if (Event.Type == HWInstructionEvent::Dispatched) {
    const Instruction &Inst = *Event.IR.getInstruction();
    const unsigned Index = Event.IR.getSourceIndex();
    if (LQResourceID && Inst.getMayLoad() &&
        MostRecentLoadDispatched != Index) {
      Usage[LQResourceID].SlotsInUse++;
      MostRecentLoadDispatched = Index;
    }
    if (SQResourceID && Inst.getMayStore() &&
        MostRecentStoreDispatched != Index) {
      Usage[SQResourceID].SlotsInUse++;
      MostRecentStoreDispatched = Index;
    }
  } else if (Event.Type == HWInstructionEvent::Executed) {
    const Instruction &Inst = *Event.IR.getInstruction();
    if (LQResourceID && Inst.getMayLoad()) {
      assert(Usage[LQResourceID].SlotsInUse);
      Usage[LQResourceID].SlotsInUse--;
    }
    if (SQResourceID && Inst.getMayStore()) {
      assert(Usage[SQResourceID].SlotsInUse);
      Usage[SQResourceID].SlotsInUse--;
    }
  }
}

void SchedulerStatistics::onReservedBuffers(const InstRef & /* unused */,
                                            ArrayRef<unsigned> Buffers) {
  for (const unsigned Buffer : Buffers) {
    if (Buffer == LQResourceID || Buffer == SQResourceID)
      continue;
    Usage[Buffer].SlotsInUse++;
  }
}

void SchedulerStatistics::onReleasedBuffers(const InstRef & /* unused */,
                                            ArrayRef<unsigned> Buffers) {
  for (const unsigned Buffer : Buffers) {
    if (Buffer == LQResourceID || Buffer == SQResourceID)
      continue;
    Usage[Buffer].SlotsInUse--;
  }
}

void SchedulerStatistics::updateHistograms() {
  for (BufferUsage &BU : Usage) {
    BU.CumulativeNumUsedSlots += BU.SlotsInUse;
    BU.MaxUsedSlots = std::max(BU.MaxUsedSlots, BU.SlotsInUse);
  }

  IssueWidthPerCycle[NumIssued]++;
  NumIssued = 0;
}

void SchedulerStatistics::printSchedulerStats(raw_ostream &OS) const {
  OS << "\n\nSchedulers - "
     << "number of cycles where we saw N micro opcodes issued:\n";
  OS << "[# issued], [# cycles]\n";

  bool HasColors = OS.has_colors();
  const auto It = llvm::max_element(IssueWidthPerCycle);
  for (const std::pair<const unsigned, unsigned> &Entry : IssueWidthPerCycle) {
    unsigned NumIssued = Entry.first;
    if (NumIssued == It->first && HasColors)
      OS.changeColor(raw_ostream::SAVEDCOLOR, true, false);

    unsigned IPC = Entry.second;
    OS << " " << NumIssued << ",          " << IPC << "  ("
       << format("%.1f", ((double)IPC / NumCycles) * 100) << "%)\n";
    if (HasColors)
      OS.resetColor();
  }
}

void SchedulerStatistics::printSchedulerUsage(raw_ostream &OS) const {
  assert(NumCycles && "Unexpected number of cycles!");

  OS << "\nScheduler's queue usage:\n";
  if (all_of(Usage, [](const BufferUsage &BU) { return !BU.MaxUsedSlots; })) {
    OS << "No scheduler resources used.\n";
    return;
  }

  OS << "[1] Resource name.\n"
     << "[2] Average number of used buffer entries.\n"
     << "[3] Maximum number of used buffer entries.\n"
     << "[4] Total number of buffer entries.\n\n"
     << " [1]            [2]        [3]        [4]\n";

  formatted_raw_ostream FOS(OS);
  bool HasColors = FOS.has_colors();
  for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
    const MCProcResourceDesc &ProcResource = *SM.getProcResource(I);
    if (ProcResource.BufferSize <= 0)
      continue;

    const BufferUsage &BU = Usage[I];
    double AvgUsage = (double)BU.CumulativeNumUsedSlots / NumCycles;
    double AlmostFullThreshold = (double)(ProcResource.BufferSize * 4) / 5;
    unsigned NormalizedAvg = floor((AvgUsage * 10) + 0.5) / 10;
    unsigned NormalizedThreshold = floor((AlmostFullThreshold * 10) + 0.5) / 10;

    FOS << ProcResource.Name;
    FOS.PadToColumn(17);
    if (HasColors && NormalizedAvg >= NormalizedThreshold)
      FOS.changeColor(raw_ostream::YELLOW, true, false);
    FOS << NormalizedAvg;
    if (HasColors)
      FOS.resetColor();
    FOS.PadToColumn(28);
    if (HasColors &&
        BU.MaxUsedSlots == static_cast<unsigned>(ProcResource.BufferSize))
      FOS.changeColor(raw_ostream::RED, true, false);
    FOS << BU.MaxUsedSlots;
    if (HasColors)
      FOS.resetColor();
    FOS.PadToColumn(39);
    FOS << ProcResource.BufferSize << '\n';
  }

  FOS.flush();
}

void SchedulerStatistics::printView(raw_ostream &OS) const {
  printSchedulerStats(OS);
  printSchedulerUsage(OS);
}

} // namespace mca
} // namespace llvm