1 /* 2 * Copyright (C) 2019 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SRC_PROFILING_PERF_EVENT_READER_H_ 18 #define SRC_PROFILING_PERF_EVENT_READER_H_ 19 20 #include <linux/perf_event.h> 21 #include <stdint.h> 22 #include <sys/mman.h> 23 #include <sys/types.h> 24 #include <optional> 25 26 #include "perfetto/ext/base/scoped_file.h" 27 #include "perfetto/ext/tracing/core/basic_types.h" 28 #include "src/profiling/perf/common_types.h" 29 #include "src/profiling/perf/event_config.h" 30 31 namespace perfetto { 32 namespace profiling { 33 34 class PerfRingBuffer { 35 public: 36 static std::optional<PerfRingBuffer> Allocate(int perf_fd, 37 size_t data_page_count); 38 39 ~PerfRingBuffer(); 40 41 // move-only 42 PerfRingBuffer(const PerfRingBuffer&) = delete; 43 PerfRingBuffer& operator=(const PerfRingBuffer&) = delete; 44 PerfRingBuffer(PerfRingBuffer&& other) noexcept; 45 PerfRingBuffer& operator=(PerfRingBuffer&& other) noexcept; 46 47 char* ReadRecordNonconsuming(); 48 void Consume(size_t bytes); 49 50 private: 51 PerfRingBuffer() = default; 52 valid()53 bool valid() const { return metadata_page_ != nullptr; } 54 55 // Points at the start of the mmap'd region. 56 perf_event_mmap_page* metadata_page_ = nullptr; 57 58 // Size of the mmap'd region (1 metadata page + data_buf_sz_). 59 size_t mmap_sz_ = 0; 60 61 // mmap'd ring buffer 62 char* data_buf_ = nullptr; 63 size_t data_buf_sz_ = 0; 64 65 // When a record wraps around the ring buffer boundary, it is reconstructed in 66 // a contiguous form in this buffer. This allows us to always return a pointer 67 // to a contiguous record. 68 constexpr static size_t kMaxPerfRecordSize = 1 << 16; // max size 64k 69 alignas(uint64_t) char reconstructed_record_[kMaxPerfRecordSize]; 70 }; 71 72 class EventReader { 73 public: 74 static std::optional<EventReader> ConfigureEvents( 75 uint32_t cpu, 76 const EventConfig& event_cfg); 77 78 // Consumes records from the ring buffer until either encountering a sample, 79 // or catching up to the writer. The other record of interest 80 // (PERF_RECORD_LOST) is handled via the given callback. 81 std::optional<ParsedSample> ReadUntilSample( 82 std::function<void(uint64_t)> lost_events_callback); 83 84 void EnableEvents(); 85 // Pauses the event counting, without invalidating existing samples. 86 void DisableEvents(); 87 cpu()88 uint32_t cpu() const { return cpu_; } 89 90 ~EventReader() = default; 91 92 // move-only 93 EventReader(const EventReader&) = delete; 94 EventReader& operator=(const EventReader&) = delete; 95 EventReader(EventReader&&) noexcept = default; 96 EventReader& operator=(EventReader&&) noexcept; 97 98 private: 99 EventReader(uint32_t cpu, 100 perf_event_attr event_attr, 101 base::ScopedFile perf_fd, 102 PerfRingBuffer ring_buffer); 103 104 ParsedSample ParseSampleRecord(uint32_t cpu, const char* record_start); 105 106 // All events are cpu-bound (thread-scoped events not supported). 107 const uint32_t cpu_; 108 const perf_event_attr event_attr_; 109 base::ScopedFile perf_fd_; 110 PerfRingBuffer ring_buffer_; 111 }; 112 113 } // namespace profiling 114 } // namespace perfetto 115 116 #endif // SRC_PROFILING_PERF_EVENT_READER_H_ 117