[llvm-exegesis] Refactor individual counter data to ConfiguredEvent

[boomanaiden154]

This further sets things up for validation events. Having a separate abstraction for a configured event that is setup as a counter allows for much easier creation of more events in the future within a single counter group (like validation counters) without duplicating any code.

[llvmbot]

@llvm/pr-subscribers-tools-llvm-exegesis

Author: Aiden Grossman (boomanaiden154)

Changes

This further sets things up for validation events. Having a separate abstraction for a configured event that is setup as a counter allows for much easier creation of more events in the future within a single counter group (like validation counters) without duplicating any code.

---

Full diff: https://github.com/llvm/llvm-project/pull/77900.diff

3 Files Affected:

• (modified) llvm/tools/llvm-exegesis/lib/PerfHelper.cpp (+50-30)
• (modified) llvm/tools/llvm-exegesis/lib/PerfHelper.h (+27-5)
• (modified) llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp (+4-4)

diff --git a/llvm/tools/llvm-exegesis/lib/PerfHelper.cpp b/llvm/tools/llvm-exegesis/lib/PerfHelper.cpp
index f6e091bdff9aec..1dab8809d30280 100644
--- a/llvm/tools/llvm-exegesis/lib/PerfHelper.cpp
+++ b/llvm/tools/llvm-exegesis/lib/PerfHelper.cpp
@@ -107,21 +107,18 @@ StringRef PerfEvent::getPfmEventString() const {
   return FullQualifiedEventString;
 }
 
-CounterGroup::CounterGroup(PerfEvent &&E, pid_t ProcessID)
-    : Event(std::move(E)) {
+ConfiguredEvent::ConfiguredEvent(PerfEvent &&EventToConfigure)
+    : Event(std::move(EventToConfigure)) {
   assert(Event.valid());
-  IsDummyEvent = Event.name() == PerfEvent::DummyEventString;
-  if (!IsDummyEvent)
-    initRealEvent(E, ProcessID);
 }
 
 #ifdef HAVE_LIBPFM
-void CounterGroup::initRealEvent(const PerfEvent &E, pid_t ProcessID) {
-  const int Cpu = -1;     // measure any processor.
-  const int GroupFd = -1; // no grouping of counters.
+void ConfiguredEvent::initRealEvent(const pid_t ProcessID) {
+  const int CPU = -1;
+  const int GroupFD = -1;
   const uint32_t Flags = 0;
   perf_event_attr AttrCopy = *Event.attribute();
-  FileDescriptor = perf_event_open(&AttrCopy, ProcessID, Cpu, GroupFd, Flags);
+  FileDescriptor = perf_event_open(&AttrCopy, ProcessID, CPU, GroupFD, Flags);
   if (FileDescriptor == -1) {
     errs() << "Unable to open event. ERRNO: " << strerror(errno)
            << ". Make sure your kernel allows user "
@@ -134,44 +131,67 @@ void CounterGroup::initRealEvent(const PerfEvent &E, pid_t ProcessID) {
   assert(FileDescriptor != -1 && "Unable to open event");
 }
 
-CounterGroup::~CounterGroup() {
+Expected<SmallVector<int64_t>>
+ConfiguredEvent::readOrError(StringRef /*unused*/) const {
+  int64_t Count = 0;
+  ssize_t ReadSize = ::read(FileDescriptor, &Count, sizeof(Count));
+
+  if (ReadSize != sizeof(Count))
+    return llvm::make_error<llvm::StringError>("Failed to read event counter",
+                                               llvm::errc::io_error);
+
+  SmallVector<int64_t, 1> Result;
+  Result.push_back(Count);
+  return Result;
+}
+
+ConfiguredEvent::~ConfiguredEvent() { close(FileDescriptor); }
+#else
+void ConfiguredEvent::initRealEvent(pid_t ProcessID) {}
+
+Expected<SmallVector<int64_t>>
+ConfiguredEvent::readOrError(StringRef /*unused*/) const {
+  return make_error<StringError>("Not implemented",
+                                 errc::function_not_supported);
+}
+
+ConfiguredEvent::~ConfiguredEvent() = default;
+#endif // HAVE_LIBPFM
+
+CounterGroup::CounterGroup(PerfEvent &&E, pid_t ProcessID)
+    : EventCounter(std::move(E)) {
+  IsDummyEvent = EventCounter.isDummyEvent();
   if (!IsDummyEvent)
-    close(FileDescriptor);
+    initRealEvent(ProcessID);
+}
+
+#ifdef HAVE_LIBPFM
+void CounterGroup::initRealEvent(pid_t ProcessID) {
+  EventCounter.initRealEvent(ProcessID);
 }
 
 void CounterGroup::start() {
   if (!IsDummyEvent)
-    ioctl(FileDescriptor, PERF_EVENT_IOC_RESET, 0);
+    ioctl(getFileDescriptor(), PERF_EVENT_IOC_RESET, 0);
 }
 
 void CounterGroup::stop() {
   if (!IsDummyEvent)
-    ioctl(FileDescriptor, PERF_EVENT_IOC_DISABLE, 0);
+    ioctl(getFileDescriptor(), PERF_EVENT_IOC_DISABLE, 0);
 }
 
 llvm::Expected<llvm::SmallVector<int64_t, 4>>
-CounterGroup::readOrError(StringRef /*unused*/) const {
-  int64_t Count = 0;
-  if (!IsDummyEvent) {
-    ssize_t ReadSize = ::read(FileDescriptor, &Count, sizeof(Count));
-    if (ReadSize != sizeof(Count))
-      return llvm::make_error<llvm::StringError>("Failed to read event counter",
-                                                 llvm::errc::io_error);
-  } else {
-    Count = 42;
-  }
-
-  llvm::SmallVector<int64_t, 4> Result;
-  Result.push_back(Count);
-  return Result;
+CounterGroup::readOrError(StringRef FunctionBytes) const {
+  if (!IsDummyEvent)
+    return EventCounter.readOrError(FunctionBytes);
+  else
+    return SmallVector<int64_t, 1>(1, 42);
 }
 
 int CounterGroup::numValues() const { return 1; }
 #else
 
-void CounterGroup::initRealEvent(const PerfEvent &, pid_t ProcessID) {}
-
-CounterGroup::~CounterGroup() = default;
+void CounterGroup::initRealEvent(pid_t ProcessID) {}
 
 void CounterGroup::start() {}
 
diff --git a/llvm/tools/llvm-exegesis/lib/PerfHelper.h b/llvm/tools/llvm-exegesis/lib/PerfHelper.h
index daf2fbd0e3abc8..e9b73da3836287 100644
--- a/llvm/tools/llvm-exegesis/lib/PerfHelper.h
+++ b/llvm/tools/llvm-exegesis/lib/PerfHelper.h
@@ -77,6 +77,29 @@ class PerfEvent {
   void initRealEvent(StringRef PfmEventString);
 };
 
+// Represents a single event that has been configured in the Linux perf
+// subsystem.
+class ConfiguredEvent {
+public:
+  ConfiguredEvent(PerfEvent &&EventToConfigure);
+
+  void initRealEvent(const pid_t ProcessID);
+  Expected<SmallVector<int64_t>> readOrError(StringRef FunctionBytes) const;
+  int getFileDescriptor() const { return FileDescriptor; }
+  bool isDummyEvent() const {
+    return Event.name() == PerfEvent::DummyEventString;
+  }
+
+  ConfiguredEvent(const ConfiguredEvent &) = delete;
+  ConfiguredEvent(ConfiguredEvent &&other) = default;
+
+  ~ConfiguredEvent();
+
+private:
+  PerfEvent Event;
+  int FileDescriptor = -1;
+};
+
 // Consists of a counter measuring a specific event and associated validation
 // counters measuring execution conditions. All counters in a group are part
 // of a single event group and are thus scheduled on and off the CPU as a single
@@ -89,7 +112,7 @@ class CounterGroup {
   CounterGroup(const CounterGroup &) = delete;
   CounterGroup(CounterGroup &&other) = default;
 
-  virtual ~CounterGroup();
+  virtual ~CounterGroup() = default;
 
   /// Starts the measurement of the event.
   virtual void start();
@@ -108,15 +131,14 @@ class CounterGroup {
 
   virtual int numValues() const;
 
-  int getFileDescriptor() const { return FileDescriptor; }
+  int getFileDescriptor() const { return EventCounter.getFileDescriptor(); }
 
 protected:
-  PerfEvent Event;
-  int FileDescriptor = -1;
+  ConfiguredEvent EventCounter;
   bool IsDummyEvent;
 
 private:
-  void initRealEvent(const PerfEvent &E, pid_t ProcessID);
+  void initRealEvent(pid_t ProcessID);
 };
 
 } // namespace pfm
diff --git a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
index 55ca2d7146ceb7..96fb0f085a1ee1 100644
--- a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
+++ b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
@@ -143,7 +143,7 @@ X86LbrPerfEvent::X86LbrPerfEvent(unsigned SamplingPeriod) {
 X86LbrCounter::X86LbrCounter(pfm::PerfEvent &&NewEvent)
     : CounterGroup(std::move(NewEvent)) {
   MMappedBuffer = mmap(nullptr, kMappedBufferSize, PROT_READ | PROT_WRITE,
-                       MAP_SHARED, FileDescriptor, 0);
+                       MAP_SHARED, getFileDescriptor(), 0);
   if (MMappedBuffer == MAP_FAILED)
     llvm::errs() << "Failed to mmap buffer.";
 }
@@ -154,7 +154,7 @@ X86LbrCounter::~X86LbrCounter() {
 }
 
 void X86LbrCounter::start() {
-  ioctl(FileDescriptor, PERF_EVENT_IOC_REFRESH, 1024 /* kMaxPollsPerFd */);
+  ioctl(getFileDescriptor(), PERF_EVENT_IOC_REFRESH, 1024 /* kMaxPollsPerFd */);
 }
 
 llvm::Error X86LbrCounter::checkLbrSupport() {
@@ -197,7 +197,7 @@ llvm::Error X86LbrCounter::checkLbrSupport() {
 llvm::Expected<llvm::SmallVector<int64_t, 4>>
 X86LbrCounter::readOrError(StringRef FunctionBytes) const {
   // Disable the event before reading
-  ioctl(FileDescriptor, PERF_EVENT_IOC_DISABLE, 0);
+  ioctl(getFileDescriptor(), PERF_EVENT_IOC_DISABLE, 0);
 
   // Find the boundary of the function so that we could filter the LBRs
   // to keep only the relevant records.
@@ -223,7 +223,7 @@ X86LbrCounter::doReadCounter(const void *From, const void *To) const {
   int PollResult = 0;
 
   while (PollResult <= 0) {
-    PollResult = pollLbrPerfEvent(FileDescriptor);
+    PollResult = pollLbrPerfEvent(getFileDescriptor());
     if (PollResult > 0)
       break;
     if (PollResult == -1)