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| //===-- PerfHelper.h ------------------------------------------*- 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
/// Helpers for measuring perf events.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
#define LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/config.h"
#include <functional>
#include <memory>
struct perf_event_attr;
namespace llvm {
namespace exegesis {
namespace pfm {
// Returns true on error.
bool pfmInitialize();
void pfmTerminate();
// Retrieves the encoding for the event described by pfm_event_string.
// NOTE: pfm_initialize() must be called before creating PerfEvent objects.
class PerfEvent {
public:
// http://perfmon2.sourceforge.net/manv4/libpfm.html
// Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
explicit PerfEvent(StringRef pfm_event_string);
PerfEvent(const PerfEvent &) = delete;
PerfEvent(PerfEvent &&other);
~PerfEvent();
// The pfm_event_string passed at construction time.
StringRef name() const;
// Whether the event was successfully created.
bool valid() const;
// The encoded event to be passed to the Kernel.
const perf_event_attr *attribute() const;
// The fully qualified name for the event.
// e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
StringRef getPfmEventString() const;
private:
const std::string EventString;
std::string FullQualifiedEventString;
perf_event_attr *Attr;
};
// Uses a valid PerfEvent to configure the Kernel so we can measure the
// underlying event.
struct Counter {
// event: the PerfEvent to measure.
explicit Counter(const PerfEvent &event);
Counter(const Counter &) = delete;
Counter(Counter &&other) = default;
~Counter();
void start(); // Starts the measurement of the event.
void stop(); // Stops the measurement of the event.
int64_t read() const; // Return the current value of the counter.
private:
#ifdef HAVE_LIBPFM
int FileDescriptor = -1;
#endif
};
// Helper to measure a list of PerfEvent for a particular function.
// callback is called for each successful measure (PerfEvent needs to be valid).
template <typename Function>
void Measure(
ArrayRef<PerfEvent> Events,
const std::function<void(const PerfEvent &Event, int64_t Value)> &Callback,
Function Fn) {
for (const auto &Event : Events) {
if (!Event.valid())
continue;
Counter Cnt(Event);
Cnt.start();
Fn();
Cnt.stop();
Callback(Event, Cnt.read());
}
}
} // namespace pfm
} // namespace exegesis
} // namespace llvm
#endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
|