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/SmallVector.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/Config/config.h"
  20 #include "llvm/Support/Error.h"
  21
  22 #include <cstdint>
  23 #include <functional>
  24 #include <memory>
  25
  26 #ifdef _MSC_VER
  27 typedef int pid_t;
  28 #else
  29 #include <sys/types.h>
  30 #endif // _MSC_VER
  31
  32 struct perf_event_attr;
  33
  34 namespace llvm {
  35 namespace exegesis {
  36 namespace pfm {
  37
  38 // Returns true on error.
  39 bool pfmInitialize();
  40 void pfmTerminate();
  41
  42 // Retrieves the encoding for the event described by pfm_event_string.
  43 // NOTE: pfm_initialize() must be called before creating PerfEvent objects.
  44 class PerfEvent {
  45 public:
  46   // Dummy event that does not require access to counters (for tests).
  47   static const char *const DummyEventString;
  48
  49   // http://perfmon2.sourceforge.net/manv4/libpfm.html
  50   // Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
  51   explicit PerfEvent(StringRef PfmEventString);
  52
  53   PerfEvent(const PerfEvent &) = delete;
  54   PerfEvent(PerfEvent &&other);
  55   ~PerfEvent();
  56
  57   // The pfm_event_string passed at construction time.
  58   StringRef name() const;
  59
  60   // Whether the event was successfully created.
  61   bool valid() const;
  62
  63   // The encoded event to be passed to the Kernel.
  64   const perf_event_attr *attribute() const;
  65
  66   // The fully qualified name for the event.
  67   // e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
  68   StringRef getPfmEventString() const;
  69
  70 protected:
  71   PerfEvent() = default;
  72   std::string EventString;
  73   std::string FullQualifiedEventString;
  74   perf_event_attr *Attr;
  75
  76 private:
  77   void initRealEvent(StringRef PfmEventString);
  78 };
  79
  80 // Uses a valid PerfEvent to configure the Kernel so we can measure the
  81 // underlying event.
  82 class Counter {
  83 public:
  84   // event: the PerfEvent to measure.
  85   explicit Counter(PerfEvent &&event, pid_t ProcessID = 0);
  86
  87   Counter(const Counter &) = delete;
  88   Counter(Counter &&other) = default;
  89
  90   virtual ~Counter();
  91
  92   /// Starts the measurement of the event.
  93   virtual void start();
  94
  95   /// Stops the measurement of the event.
  96   void stop();
  97
  98   /// Returns the current value of the counter or -1 if it cannot be read.
  99   int64_t read() const;
 100
 101   /// Returns the current value of the counter or error if it cannot be read.
 102   /// FunctionBytes: The benchmark function being executed.
 103   /// This is used to filter out the measurements to ensure they are only
 104   /// within the benchmarked code.
 105   /// If empty (or not specified), then no filtering will be done.
 106   /// Not all counters choose to use this.
 107   virtual llvm::Expected<llvm::SmallVector<int64_t, 4>>
 108   readOrError(StringRef FunctionBytes = StringRef()) const;
 109
 110   virtual int numValues() const;
 111
 112   int getFileDescriptor() const { return FileDescriptor; }
 113
 114 protected:
 115   PerfEvent Event;
 116   int FileDescriptor = -1;
 117   bool IsDummyEvent;
 118
 119 private:
 120   void initRealEvent(const PerfEvent &E, pid_t ProcessID);
 121 };
 122
 123 } // namespace pfm
 124 } // namespace exegesis
 125 } // namespace llvm
 126
 127 #endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H