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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/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Error.h"
#include <cstdint>
#include <functional>
#include <memory>
#ifdef _MSC_VER
typedef int pid_t;
#else
#include <sys/types.h>
#endif // _MSC_VER
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:
// Dummy event that does not require access to counters (for tests).
static const char *const DummyEventString;
// http://perfmon2.sourceforge.net/manv4/libpfm.html
// Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
explicit PerfEvent(StringRef PfmEventString);
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;
protected:
PerfEvent() = default;
std::string EventString;
std::string FullQualifiedEventString;
perf_event_attr *Attr;
private:
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, const int GroupFD = -1);
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
// unit.
class CounterGroup {
public:
// event: the PerfEvent to measure.
explicit CounterGroup(PerfEvent &&event, std::vector<PerfEvent> &&ValEvents,
pid_t ProcessID = 0);
CounterGroup(const CounterGroup &) = delete;
CounterGroup(CounterGroup &&other) = default;
virtual ~CounterGroup() = default;
/// Starts the measurement of the event.
virtual void start();
/// Stops the measurement of the event.
void stop();
/// Returns the current value of the counter or error if it cannot be read.
/// FunctionBytes: The benchmark function being executed.
/// This is used to filter out the measurements to ensure they are only
/// within the benchmarked code.
/// If empty (or not specified), then no filtering will be done.
/// Not all counters choose to use this.
virtual Expected<SmallVector<int64_t, 4>>
readOrError(StringRef FunctionBytes = StringRef()) const;
virtual Expected<SmallVector<int64_t>> readValidationCountersOrError() const;
virtual int numValues() const;
int getFileDescriptor() const { return EventCounter.getFileDescriptor(); }
protected:
ConfiguredEvent EventCounter;
bool IsDummyEvent;
std::vector<ConfiguredEvent> ValidationEventCounters;
private:
void initRealEvent(pid_t ProcessID);
};
} // namespace pfm
} // namespace exegesis
} // namespace llvm
#endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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