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 113