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 #define ATRACE_TAG ATRACE_TAG_ALWAYS 17 #include "event_fd.h" 18 19 #include <fcntl.h> 20 #include <stdio.h> 21 #include <string.h> 22 #include <sys/ioctl.h> 23 #include <sys/mman.h> 24 #include <sys/syscall.h> 25 #include <sys/types.h> 26 #include <atomic> 27 #include <memory> 28 #include <cutils/trace.h> 29 #include <utils/Trace.h> 30 31 #include <android-base/file.h> 32 #include <android-base/logging.h> 33 #include <android-base/stringprintf.h> 34 35 #include "environment.h" 36 #include "event_attr.h" 37 #include "event_type.h" 38 #include "perf_event.h" 39 #include "utils.h" 40 41 static int perf_event_open(const perf_event_attr& attr, pid_t pid, int cpu, 42 int group_fd, unsigned long flags) { // NOLINT 43 return syscall(__NR_perf_event_open, &attr, pid, cpu, group_fd, flags); 44 } 45 46 std::unique_ptr<EventFd> EventFd::OpenEventFile(const perf_event_attr& attr, 47 pid_t tid, int cpu, 48 EventFd* group_event_fd, 49 bool report_error) { 50 std::string event_name = GetEventNameByAttr(attr); 51 int group_fd = -1; 52 if (group_event_fd != nullptr) { 53 group_fd = group_event_fd->perf_event_fd_; 54 } 55 perf_event_attr real_attr = attr; 56 if (attr.freq) { 57 uint64_t max_sample_freq; 58 if (GetMaxSampleFrequency(&max_sample_freq) && max_sample_freq < attr.sample_freq) { 59 PLOG(INFO) << "Adjust sample freq to max allowed sample freq " << max_sample_freq; 60 real_attr.sample_freq = max_sample_freq; 61 } 62 } 63 int perf_event_fd = perf_event_open(real_attr, tid, cpu, group_fd, 0); 64 if (perf_event_fd == -1) { 65 if (report_error) { 66 PLOG(ERROR) << "open perf_event_file (event " << event_name << ", tid " 67 << tid << ", cpu " << cpu << ", group_fd " << group_fd 68 << ") failed"; 69 } else { 70 PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", tid " 71 << tid << ", cpu " << cpu << ", group_fd " << group_fd 72 << ") failed"; 73 } 74 return nullptr; 75 } 76 if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) { 77 if (report_error) { 78 PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " 79 << event_name << ", tid " << tid << ", cpu " << cpu 80 << ", group_fd " << group_fd << ") failed"; 81 } else { 82 PLOG(DEBUG) << "fcntl(FD_CLOEXEC) for perf_event_file (event " 83 << event_name << ", tid " << tid << ", cpu " << cpu 84 << ", group_fd " << group_fd << ") failed"; 85 } 86 return nullptr; 87 } 88 return std::unique_ptr<EventFd>( 89 new EventFd(real_attr, perf_event_fd, event_name, tid, cpu)); 90 } 91 92 EventFd::~EventFd() { 93 DestroyMappedBuffer(); 94 close(perf_event_fd_); 95 } 96 97 std::string EventFd::Name() const { 98 return android::base::StringPrintf( 99 "perf_event_file(event %s, tid %d, cpu %d)", event_name_.c_str(), tid_, 100 cpu_); 101 } 102 103 uint64_t EventFd::Id() const { 104 if (id_ == 0) { 105 PerfCounter counter; 106 if (ReadCounter(&counter)) { 107 id_ = counter.id; 108 } 109 } 110 return id_; 111 } 112 113 bool EventFd::EnableEvent() { 114 int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_ENABLE, 0); 115 if (result < 0) { 116 PLOG(ERROR) << "ioctl(enable) " << Name() << " failed"; 117 return false; 118 } 119 return true; 120 } 121 122 bool EventFd::ReadCounter(PerfCounter* counter) const { 123 CHECK(counter != nullptr); 124 uint64_t pre_counter = counter->value; 125 if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) { 126 PLOG(ERROR) << "ReadCounter from " << Name() << " failed"; 127 return false; 128 } 129 // Trace is always available to systrace if enabled 130 if (tid_ > 0) { 131 ATRACE_INT64(android::base::StringPrintf( 132 "%s_tid%d_cpu%d", event_name_.c_str(), tid_, 133 cpu_).c_str(), counter->value - pre_counter); 134 } else { 135 ATRACE_INT64(android::base::StringPrintf( 136 "%s_cpu%d", event_name_.c_str(), 137 cpu_).c_str(), counter->value - pre_counter); 138 } 139 return true; 140 } 141 142 bool EventFd::CreateMappedBuffer(size_t mmap_pages, bool report_error) { 143 CHECK(IsPowerOfTwo(mmap_pages)); 144 size_t page_size = sysconf(_SC_PAGE_SIZE); 145 size_t mmap_len = (mmap_pages + 1) * page_size; 146 void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, 147 perf_event_fd_, 0); 148 if (mmap_addr == MAP_FAILED) { 149 bool is_perm_error = (errno == EPERM); 150 if (report_error) { 151 PLOG(ERROR) << "mmap(" << mmap_pages << ") failed for " << Name(); 152 } else { 153 PLOG(DEBUG) << "mmap(" << mmap_pages << ") failed for " << Name(); 154 } 155 if (report_error && is_perm_error) { 156 LOG(ERROR) 157 << "It seems the kernel doesn't allow allocating enough " 158 << "buffer for dumping samples, consider decreasing mmap pages(-m)."; 159 } 160 return false; 161 } 162 mmap_addr_ = mmap_addr; 163 mmap_len_ = mmap_len; 164 mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_); 165 mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size; 166 mmap_data_buffer_size_ = mmap_len_ - page_size; 167 return true; 168 } 169 170 bool EventFd::ShareMappedBuffer(const EventFd& event_fd, bool report_error) { 171 CHECK(!HasMappedBuffer()); 172 CHECK(event_fd.HasMappedBuffer()); 173 int result = 174 ioctl(perf_event_fd_, PERF_EVENT_IOC_SET_OUTPUT, event_fd.perf_event_fd_); 175 if (result != 0) { 176 if (report_error) { 177 PLOG(ERROR) << "failed to share mapped buffer of " 178 << event_fd.perf_event_fd_ << " with " << perf_event_fd_; 179 } 180 return false; 181 } 182 return true; 183 } 184 185 void EventFd::DestroyMappedBuffer() { 186 if (HasMappedBuffer()) { 187 munmap(mmap_addr_, mmap_len_); 188 mmap_addr_ = nullptr; 189 mmap_len_ = 0; 190 mmap_metadata_page_ = nullptr; 191 mmap_data_buffer_ = nullptr; 192 mmap_data_buffer_size_ = 0; 193 } 194 } 195 196 size_t EventFd::GetAvailableMmapData(std::vector<char>& buffer, size_t& buffer_pos) { 197 if (!HasMappedBuffer()) { 198 return 0; 199 } 200 // The mmap_data_buffer is used as a ring buffer between the kernel and 201 // simpleperf. The kernel continuously writes records to the buffer, and 202 // simpleperf continuously read records out. 203 // _________________________________________ 204 // buffer | can write | can read | can write | 205 // ^ ^ 206 // read_head write_head 207 // 208 // So simpleperf can read records in [read_head, write_head), and the kernel 209 // can write records in [write_head, read_head). The kernel is responsible 210 // for updating write_head, and simpleperf is responsible for updating 211 // read_head. 212 213 size_t buf_mask = mmap_data_buffer_size_ - 1; 214 size_t write_head = 215 static_cast<size_t>(mmap_metadata_page_->data_head & buf_mask); 216 size_t read_head = 217 static_cast<size_t>(mmap_metadata_page_->data_tail & buf_mask); 218 219 if (read_head == write_head) { 220 // No available data. 221 return 0; 222 } 223 size_t read_bytes; 224 if (read_head < write_head) { 225 read_bytes = write_head - read_head; 226 } else { 227 read_bytes = mmap_data_buffer_size_ - read_head + write_head; 228 } 229 // Extend the buffer if it is not big enough. 230 if (buffer.size() < buffer_pos + read_bytes) { 231 buffer.resize(buffer_pos + read_bytes); 232 } 233 234 // rmb() used to ensure reading data after reading data_head. 235 __sync_synchronize(); 236 237 // Copy records from mapped buffer. Note that records can be wrapped at the 238 // end of the mapped buffer. 239 char* to = &buffer[buffer_pos]; 240 if (read_head < write_head) { 241 char* from = mmap_data_buffer_ + read_head; 242 size_t n = write_head - read_head; 243 memcpy(to, from, n); 244 } else { 245 char* from = mmap_data_buffer_ + read_head; 246 size_t n = mmap_data_buffer_size_ - read_head; 247 memcpy(to, from, n); 248 to += n; 249 from = mmap_data_buffer_; 250 n = write_head; 251 memcpy(to, from, n); 252 } 253 buffer_pos += read_bytes; 254 DiscardMmapData(read_bytes); 255 return read_bytes; 256 } 257 258 void EventFd::DiscardMmapData(size_t discard_size) { 259 // mb() used to ensure finish reading data before writing data_tail. 260 __sync_synchronize(); 261 mmap_metadata_page_->data_tail += discard_size; 262 } 263 264 bool EventFd::StartPolling(IOEventLoop& loop, 265 const std::function<bool()>& callback) { 266 ioevent_ref_ = loop.AddReadEvent(perf_event_fd_, callback); 267 return ioevent_ref_ != nullptr; 268 } 269 270 bool EventFd::StopPolling() { return IOEventLoop::DelEvent(ioevent_ref_); } 271 272 bool IsEventAttrSupported(const perf_event_attr& attr) { 273 if (attr.type == SIMPLEPERF_TYPE_USER_SPACE_SAMPLERS && 274 attr.config == SIMPLEPERF_CONFIG_INPLACE_SAMPLER) { 275 // User space samplers don't need kernel support. 276 return true; 277 } 278 std::unique_ptr<EventFd> event_fd = EventFd::OpenEventFile(attr, getpid(), -1, nullptr, false); 279 return event_fd != nullptr; 280 } 281
