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 static bool warned = false; 60 if (!warned) { 61 warned = true; 62 LOG(INFO) << "Adjust sample freq to max allowed sample freq " << max_sample_freq; 63 } 64 real_attr.sample_freq = max_sample_freq; 65 } 66 } 67 int perf_event_fd = perf_event_open(real_attr, tid, cpu, group_fd, 0); 68 if (perf_event_fd == -1) { 69 if (report_error) { 70 PLOG(ERROR) << "open perf_event_file (event " << event_name << ", tid " 71 << tid << ", cpu " << cpu << ", group_fd " << group_fd 72 << ") failed"; 73 } else { 74 PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", tid " 75 << tid << ", cpu " << cpu << ", group_fd " << group_fd 76 << ") failed"; 77 } 78 return nullptr; 79 } 80 if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) { 81 if (report_error) { 82 PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " 83 << event_name << ", tid " << tid << ", cpu " << cpu 84 << ", group_fd " << group_fd << ") failed"; 85 } else { 86 PLOG(DEBUG) << "fcntl(FD_CLOEXEC) for perf_event_file (event " 87 << event_name << ", tid " << tid << ", cpu " << cpu 88 << ", group_fd " << group_fd << ") failed"; 89 } 90 return nullptr; 91 } 92 return std::unique_ptr<EventFd>( 93 new EventFd(real_attr, perf_event_fd, event_name, tid, cpu)); 94 } 95 96 EventFd::~EventFd() { 97 DestroyMappedBuffer(); 98 close(perf_event_fd_); 99 } 100 101 std::string EventFd::Name() const { 102 return android::base::StringPrintf( 103 "perf_event_file(event %s, tid %d, cpu %d)", event_name_.c_str(), tid_, 104 cpu_); 105 } 106 107 uint64_t EventFd::Id() const { 108 if (id_ == 0) { 109 PerfCounter counter; 110 if (InnerReadCounter(&counter)) { 111 id_ = counter.id; 112 } 113 } 114 return id_; 115 } 116 117 bool EventFd::EnableEvent() { 118 int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_ENABLE, 0); 119 if (result < 0) { 120 PLOG(ERROR) << "ioctl(enable) " << Name() << " failed"; 121 return false; 122 } 123 return true; 124 } 125 126 bool EventFd::InnerReadCounter(PerfCounter* counter) const { 127 CHECK(counter != nullptr); 128 if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) { 129 PLOG(ERROR) << "ReadCounter from " << Name() << " failed"; 130 return false; 131 } 132 return true; 133 } 134 135 bool EventFd::ReadCounter(PerfCounter* counter) { 136 if (!InnerReadCounter(counter)) { 137 return false; 138 } 139 // Trace is always available to systrace if enabled 140 if (tid_ > 0) { 141 ATRACE_INT64(android::base::StringPrintf( 142 "%s_tid%d_cpu%d", event_name_.c_str(), tid_, 143 cpu_).c_str(), counter->value - last_counter_value_); 144 } else { 145 ATRACE_INT64(android::base::StringPrintf( 146 "%s_cpu%d", event_name_.c_str(), 147 cpu_).c_str(), counter->value - last_counter_value_); 148 } 149 last_counter_value_ = counter->value; 150 return true; 151 } 152 153 bool EventFd::CreateMappedBuffer(size_t mmap_pages, bool report_error) { 154 CHECK(IsPowerOfTwo(mmap_pages)); 155 size_t page_size = sysconf(_SC_PAGE_SIZE); 156 size_t mmap_len = (mmap_pages + 1) * page_size; 157 void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, 158 perf_event_fd_, 0); 159 if (mmap_addr == MAP_FAILED) { 160 bool is_perm_error = (errno == EPERM); 161 if (report_error) { 162 PLOG(ERROR) << "mmap(" << mmap_pages << ") failed for " << Name(); 163 } else { 164 PLOG(DEBUG) << "mmap(" << mmap_pages << ") failed for " << Name(); 165 } 166 if (report_error && is_perm_error) { 167 LOG(ERROR) 168 << "It seems the kernel doesn't allow allocating enough " 169 << "buffer for dumping samples, consider decreasing mmap pages(-m)."; 170 } 171 return false; 172 } 173 mmap_addr_ = mmap_addr; 174 mmap_len_ = mmap_len; 175 mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_); 176 mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size; 177 mmap_data_buffer_size_ = mmap_len_ - page_size; 178 return true; 179 } 180 181 bool EventFd::ShareMappedBuffer(const EventFd& event_fd, bool report_error) { 182 CHECK(!HasMappedBuffer()); 183 CHECK(event_fd.HasMappedBuffer()); 184 int result = 185 ioctl(perf_event_fd_, PERF_EVENT_IOC_SET_OUTPUT, event_fd.perf_event_fd_); 186 if (result != 0) { 187 if (report_error) { 188 PLOG(ERROR) << "failed to share mapped buffer of " 189 << event_fd.perf_event_fd_ << " with " << perf_event_fd_; 190 } 191 return false; 192 } 193 return true; 194 } 195 196 void EventFd::DestroyMappedBuffer() { 197 if (HasMappedBuffer()) { 198 munmap(mmap_addr_, mmap_len_); 199 mmap_addr_ = nullptr; 200 mmap_len_ = 0; 201 mmap_metadata_page_ = nullptr; 202 mmap_data_buffer_ = nullptr; 203 mmap_data_buffer_size_ = 0; 204 } 205 } 206 207 size_t EventFd::GetAvailableMmapData(std::vector<char>& buffer, size_t& buffer_pos) { 208 if (!HasMappedBuffer()) { 209 return 0; 210 } 211 // The mmap_data_buffer is used as a ring buffer between the kernel and 212 // simpleperf. The kernel continuously writes records to the buffer, and 213 // simpleperf continuously read records out. 214 // _________________________________________ 215 // buffer | can write | can read | can write | 216 // ^ ^ 217 // read_head write_head 218 // 219 // So simpleperf can read records in [read_head, write_head), and the kernel 220 // can write records in [write_head, read_head). The kernel is responsible 221 // for updating write_head, and simpleperf is responsible for updating 222 // read_head. 223 224 size_t buf_mask = mmap_data_buffer_size_ - 1; 225 size_t write_head = 226 static_cast<size_t>(mmap_metadata_page_->data_head & buf_mask); 227 size_t read_head = 228 static_cast<size_t>(mmap_metadata_page_->data_tail & buf_mask); 229 230 if (read_head == write_head) { 231 // No available data. 232 return 0; 233 } 234 size_t read_bytes; 235 if (read_head < write_head) { 236 read_bytes = write_head - read_head; 237 } else { 238 read_bytes = mmap_data_buffer_size_ - read_head + write_head; 239 } 240 // Extend the buffer if it is not big enough. 241 if (buffer.size() < buffer_pos + read_bytes) { 242 buffer.resize(buffer_pos + read_bytes); 243 } 244 245 // rmb() used to ensure reading data after reading data_head. 246 __sync_synchronize(); 247 248 // Copy records from mapped buffer. Note that records can be wrapped at the 249 // end of the mapped buffer. 250 char* to = &buffer[buffer_pos]; 251 if (read_head < write_head) { 252 char* from = mmap_data_buffer_ + read_head; 253 size_t n = write_head - read_head; 254 memcpy(to, from, n); 255 } else { 256 char* from = mmap_data_buffer_ + read_head; 257 size_t n = mmap_data_buffer_size_ - read_head; 258 memcpy(to, from, n); 259 to += n; 260 from = mmap_data_buffer_; 261 n = write_head; 262 memcpy(to, from, n); 263 } 264 buffer_pos += read_bytes; 265 DiscardMmapData(read_bytes); 266 return read_bytes; 267 } 268 269 void EventFd::DiscardMmapData(size_t discard_size) { 270 // mb() used to ensure finish reading data before writing data_tail. 271 __sync_synchronize(); 272 mmap_metadata_page_->data_tail += discard_size; 273 } 274 275 bool EventFd::StartPolling(IOEventLoop& loop, 276 const std::function<bool()>& callback) { 277 ioevent_ref_ = loop.AddReadEvent(perf_event_fd_, callback); 278 return ioevent_ref_ != nullptr; 279 } 280 281 bool EventFd::StopPolling() { return IOEventLoop::DelEvent(ioevent_ref_); } 282 283 bool IsEventAttrSupported(const perf_event_attr& attr) { 284 if (attr.type == SIMPLEPERF_TYPE_USER_SPACE_SAMPLERS && 285 attr.config == SIMPLEPERF_CONFIG_INPLACE_SAMPLER) { 286 // User space samplers don't need kernel support. 287 return true; 288 } 289 std::unique_ptr<EventFd> event_fd = EventFd::OpenEventFile(attr, getpid(), -1, nullptr, false); 290 return event_fd != nullptr; 291 } 292
