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