1 /* 2 * Copyright (C) 2015 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 SIMPLE_PERF_EVENT_FD_H_ 18 #define SIMPLE_PERF_EVENT_FD_H_ 19 20 #include <sys/types.h> 21 22 #include <memory> 23 #include <string> 24 #include <vector> 25 26 #include <android-base/macros.h> 27 28 #include "perf_event.h" 29 30 struct PerfCounter { 31 uint64_t value; // The value of the event specified by the perf_event_file. 32 uint64_t time_enabled; // The enabled time. 33 uint64_t time_running; // The running time. 34 uint64_t id; // The id of the perf_event_file. 35 }; 36 37 struct pollfd; 38 39 // EventFd represents an opened perf_event_file. 40 class EventFd { 41 public: 42 static std::unique_ptr<EventFd> OpenEventFile(const perf_event_attr& attr, pid_t tid, int cpu, 43 bool report_error = true); 44 45 ~EventFd(); 46 47 uint64_t Id() const; 48 ThreadId()49 pid_t ThreadId() const { 50 return tid_; 51 } 52 Cpu()53 int Cpu() const { 54 return cpu_; 55 } 56 57 bool ReadCounter(PerfCounter* counter) const; 58 59 // Call mmap() for this perf_event_file, so we can read sampled records from mapped area. 60 // mmap_pages should be power of 2. 61 bool MmapContent(size_t mmap_pages); 62 63 // When the kernel writes new sampled records to the mapped area, we can get them by returning 64 // the start address and size of the data. 65 size_t GetAvailableMmapData(char** pdata); 66 67 // Prepare pollfd for poll() to wait on available mmap_data. 68 void PreparePollForMmapData(pollfd* poll_fd); 69 70 private: EventFd(int perf_event_fd,const std::string & event_name,pid_t tid,int cpu)71 EventFd(int perf_event_fd, const std::string& event_name, pid_t tid, int cpu) 72 : perf_event_fd_(perf_event_fd), 73 id_(0), 74 event_name_(event_name), 75 tid_(tid), 76 cpu_(cpu), 77 mmap_addr_(nullptr), 78 mmap_len_(0) { 79 } 80 81 // Give information about this perf_event_file, like (event_name, tid, cpu). 82 std::string Name() const; 83 84 // Discard how much data we have read, so the kernel can reuse this part of mapped area to store 85 // new data. 86 void DiscardMmapData(size_t discard_size); 87 88 int perf_event_fd_; 89 mutable uint64_t id_; 90 const std::string event_name_; 91 pid_t tid_; 92 int cpu_; 93 94 void* mmap_addr_; 95 size_t mmap_len_; 96 perf_event_mmap_page* mmap_metadata_page_; // The first page of mmap_area. 97 char* mmap_data_buffer_; // Starts from the second page of mmap_area, containing records written 98 // by then kernel. 99 size_t mmap_data_buffer_size_; 100 101 // As mmap_data_buffer is a ring buffer, it is possible that one record is wrapped at the 102 // end of the buffer. So we need to copy records from mmap_data_buffer to data_process_buffer 103 // before processing them. 104 static std::vector<char> data_process_buffer_; 105 106 DISALLOW_COPY_AND_ASSIGN(EventFd); 107 }; 108 109 bool IsEventAttrSupportedByKernel(perf_event_attr attr); 110 111 #endif // SIMPLE_PERF_EVENT_FD_H_ 112