llvm/tools/llvm-exegesis/lib/PerfHelper.h

   1 //===-- PerfHelper.h ------------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// Helpers for measuring perf events.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
  15 #define LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
  16
  17 #include "llvm/ADT/ArrayRef.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/Config/config.h"
  21 #include "llvm/Support/Error.h"
  22
  23 #include <cstdint>
  24 #include <functional>
  25 #include <memory>
  26
  27 struct perf_event_attr;
  28
  29 namespace llvm {
  30 namespace exegesis {
  31 namespace pfm {
  32
  33 // Returns true on error.
  34 bool pfmInitialize();
  35 void pfmTerminate();
  36
  37 // Retrieves the encoding for the event described by pfm_event_string.
  38 // NOTE: pfm_initialize() must be called before creating PerfEvent objects.
  39 class PerfEvent {
  40 public:
  41   // http://perfmon2.sourceforge.net/manv4/libpfm.html
  42   // Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
  43   explicit PerfEvent(StringRef PfmEventString);
  44
  45   PerfEvent(const PerfEvent &) = delete;
  46   PerfEvent(PerfEvent &&other);
  47   ~PerfEvent();
  48
  49   // The pfm_event_string passed at construction time.
  50   StringRef name() const;
  51
  52   // Whether the event was successfully created.
  53   bool valid() const;
  54
  55   // The encoded event to be passed to the Kernel.
  56   const perf_event_attr *attribute() const;
  57
  58   // The fully qualified name for the event.
  59   // e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
  60   StringRef getPfmEventString() const;
  61
  62 protected:
  63   PerfEvent() = default;
  64   std::string EventString;
  65   std::string FullQualifiedEventString;
  66   perf_event_attr *Attr;
  67 };
  68
  69 // Uses a valid PerfEvent to configure the Kernel so we can measure the
  70 // underlying event.
  71 class Counter {
  72 public:
  73   // event: the PerfEvent to measure.
  74   explicit Counter(PerfEvent &&event);
  75
  76   Counter(const Counter &) = delete;
  77   Counter(Counter &&other) = default;
  78
  79   virtual ~Counter();
  80
  81   /// Starts the measurement of the event.
  82   virtual void start();
  83
  84   /// Stops the measurement of the event.
  85   void stop();
  86
  87   /// Returns the current value of the counter or -1 if it cannot be read.
  88   int64_t read() const;
  89
  90   /// Returns the current value of the counter or error if it cannot be read.
  91   /// FunctionBytes: The benchmark function being executed.
  92   /// This is used to filter out the measurements to ensure they are only
  93   /// within the benchmarked code.
  94   /// If empty (or not specified), then no filtering will be done.
  95   /// Not all counters choose to use this.
  96   virtual llvm::Expected<llvm::SmallVector<int64_t, 4>>
  97   readOrError(StringRef FunctionBytes = StringRef()) const;
  98
  99   virtual int numValues() const;
 100
 101 protected:
 102   PerfEvent Event;
 103 #ifdef HAVE_LIBPFM
 104   int FileDescriptor = -1;
 105 #endif
 106 };
 107
 108 } // namespace pfm
 109 } // namespace exegesis
 110 } // namespace llvm
 111
 112 #endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H