Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 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 | */ |
Wei Wang | cf69e41 | 2016-09-29 16:34:15 -0700 | [diff] [blame] | 16 | #define ATRACE_TAG ATRACE_TAG_ALWAYS |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 17 | #include "event_fd.h" |
| 18 | |
| 19 | #include <fcntl.h> |
| 20 | #include <stdio.h> |
Yabin Cui | f469c3d | 2015-10-07 15:00:46 -0700 | [diff] [blame] | 21 | #include <string.h> |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 22 | #include <sys/ioctl.h> |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 23 | #include <sys/mman.h> |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 24 | #include <sys/syscall.h> |
| 25 | #include <sys/types.h> |
Yabin Cui | f569b47 | 2015-04-30 09:43:26 -0700 | [diff] [blame] | 26 | #include <atomic> |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 27 | #include <memory> |
Wei Wang | cf69e41 | 2016-09-29 16:34:15 -0700 | [diff] [blame] | 28 | #include <cutils/trace.h> |
| 29 | #include <utils/Trace.h> |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 30 | |
Elliott Hughes | 66dd09e | 2015-12-04 14:00:57 -0800 | [diff] [blame] | 31 | #include <android-base/file.h> |
| 32 | #include <android-base/logging.h> |
| 33 | #include <android-base/stringprintf.h> |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 34 | |
Yabin Cui | 0720d48 | 2017-03-06 17:05:50 -0800 | [diff] [blame] | 35 | #include "environment.h" |
Yabin Cui | c10a9dc | 2016-06-15 12:10:33 -0700 | [diff] [blame] | 36 | #include "event_attr.h" |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 37 | #include "event_type.h" |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 38 | #include "perf_event.h" |
| 39 | #include "utils.h" |
| 40 | |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 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); |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 44 | } |
| 45 | |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 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) { |
Yabin Cui | c10a9dc | 2016-06-15 12:10:33 -0700 | [diff] [blame] | 50 | std::string event_name = GetEventNameByAttr(attr); |
Yabin Cui | 877751b | 2016-06-13 18:03:47 -0700 | [diff] [blame] | 51 | int group_fd = -1; |
| 52 | if (group_event_fd != nullptr) { |
| 53 | group_fd = group_event_fd->perf_event_fd_; |
| 54 | } |
Yabin Cui | 0720d48 | 2017-03-06 17:05:50 -0800 | [diff] [blame] | 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); |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 64 | if (perf_event_fd == -1) { |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 65 | if (report_error) { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 66 | PLOG(ERROR) << "open perf_event_file (event " << event_name << ", tid " |
| 67 | << tid << ", cpu " << cpu << ", group_fd " << group_fd |
| 68 | << ") failed"; |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 69 | } else { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 70 | PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", tid " |
| 71 | << tid << ", cpu " << cpu << ", group_fd " << group_fd |
| 72 | << ") failed"; |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 73 | } |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 74 | return nullptr; |
| 75 | } |
| 76 | if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) { |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 77 | if (report_error) { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 78 | PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " |
| 79 | << event_name << ", tid " << tid << ", cpu " << cpu |
| 80 | << ", group_fd " << group_fd << ") failed"; |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 81 | } else { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 82 | PLOG(DEBUG) << "fcntl(FD_CLOEXEC) for perf_event_file (event " |
| 83 | << event_name << ", tid " << tid << ", cpu " << cpu |
| 84 | << ", group_fd " << group_fd << ") failed"; |
Yabin Cui | 42aa127 | 2015-09-18 11:10:55 -0700 | [diff] [blame] | 85 | } |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 86 | return nullptr; |
| 87 | } |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 88 | return std::unique_ptr<EventFd>( |
Yabin Cui | 0720d48 | 2017-03-06 17:05:50 -0800 | [diff] [blame] | 89 | new EventFd(real_attr, perf_event_fd, event_name, tid, cpu)); |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 90 | } |
| 91 | |
| 92 | EventFd::~EventFd() { |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 93 | DestroyMappedBuffer(); |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 94 | close(perf_event_fd_); |
| 95 | } |
| 96 | |
| 97 | std::string EventFd::Name() const { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 98 | return android::base::StringPrintf( |
| 99 | "perf_event_file(event %s, tid %d, cpu %d)", event_name_.c_str(), tid_, |
| 100 | cpu_); |
Yabin Cui | 67d3abd | 2015-04-16 15:26:31 -0700 | [diff] [blame] | 101 | } |
| 102 | |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 103 | uint64_t EventFd::Id() const { |
| 104 | if (id_ == 0) { |
| 105 | PerfCounter counter; |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 106 | if (InnerReadCounter(&counter)) { |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 107 | id_ = counter.id; |
| 108 | } |
| 109 | } |
| 110 | return id_; |
| 111 | } |
| 112 | |
Yabin Cui | 5633586 | 2016-04-18 13:43:20 -0700 | [diff] [blame] | 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 | |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 122 | bool EventFd::InnerReadCounter(PerfCounter* counter) const { |
Yabin Cui | 323e945 | 2015-04-20 18:07:17 -0700 | [diff] [blame] | 123 | CHECK(counter != nullptr); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 124 | if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) { |
Yabin Cui | 323e945 | 2015-04-20 18:07:17 -0700 | [diff] [blame] | 125 | PLOG(ERROR) << "ReadCounter from " << Name() << " failed"; |
| 126 | return false; |
| 127 | } |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 128 | return true; |
| 129 | } |
| 130 | |
| 131 | bool EventFd::ReadCounter(PerfCounter* counter) { |
| 132 | if (!InnerReadCounter(counter)) { |
| 133 | return false; |
| 134 | } |
Wei Wang | cf69e41 | 2016-09-29 16:34:15 -0700 | [diff] [blame] | 135 | // Trace is always available to systrace if enabled |
| 136 | if (tid_ > 0) { |
| 137 | ATRACE_INT64(android::base::StringPrintf( |
| 138 | "%s_tid%d_cpu%d", event_name_.c_str(), tid_, |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 139 | cpu_).c_str(), counter->value - last_counter_value_); |
Wei Wang | cf69e41 | 2016-09-29 16:34:15 -0700 | [diff] [blame] | 140 | } else { |
| 141 | ATRACE_INT64(android::base::StringPrintf( |
| 142 | "%s_cpu%d", event_name_.c_str(), |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 143 | cpu_).c_str(), counter->value - last_counter_value_); |
Wei Wang | cf69e41 | 2016-09-29 16:34:15 -0700 | [diff] [blame] | 144 | } |
Yabin Cui | b6b4332 | 2017-05-04 11:28:09 -0700 | [diff] [blame] | 145 | last_counter_value_ = counter->value; |
Yabin Cui | 323e945 | 2015-04-20 18:07:17 -0700 | [diff] [blame] | 146 | return true; |
| 147 | } |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 148 | |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 149 | bool EventFd::CreateMappedBuffer(size_t mmap_pages, bool report_error) { |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 150 | CHECK(IsPowerOfTwo(mmap_pages)); |
| 151 | size_t page_size = sysconf(_SC_PAGE_SIZE); |
| 152 | size_t mmap_len = (mmap_pages + 1) * page_size; |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 153 | void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, |
| 154 | perf_event_fd_, 0); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 155 | if (mmap_addr == MAP_FAILED) { |
Yabin Cui | 27816c9 | 2016-07-07 14:42:54 -0700 | [diff] [blame] | 156 | bool is_perm_error = (errno == EPERM); |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 157 | if (report_error) { |
| 158 | PLOG(ERROR) << "mmap(" << mmap_pages << ") failed for " << Name(); |
| 159 | } else { |
| 160 | PLOG(DEBUG) << "mmap(" << mmap_pages << ") failed for " << Name(); |
| 161 | } |
| 162 | if (report_error && is_perm_error) { |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 163 | LOG(ERROR) |
| 164 | << "It seems the kernel doesn't allow allocating enough " |
Yabin Cui | 825e56b | 2016-08-26 18:25:21 -0700 | [diff] [blame] | 165 | << "buffer for dumping samples, consider decreasing mmap pages(-m)."; |
Yabin Cui | 27816c9 | 2016-07-07 14:42:54 -0700 | [diff] [blame] | 166 | } |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 167 | return false; |
| 168 | } |
| 169 | mmap_addr_ = mmap_addr; |
| 170 | mmap_len_ = mmap_len; |
| 171 | mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_); |
| 172 | mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size; |
| 173 | mmap_data_buffer_size_ = mmap_len_ - page_size; |
Yabin Cui | 6173592 | 2016-07-08 13:56:48 -0700 | [diff] [blame] | 174 | return true; |
| 175 | } |
| 176 | |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 177 | bool EventFd::ShareMappedBuffer(const EventFd& event_fd, bool report_error) { |
Yabin Cui | 6173592 | 2016-07-08 13:56:48 -0700 | [diff] [blame] | 178 | CHECK(!HasMappedBuffer()); |
| 179 | CHECK(event_fd.HasMappedBuffer()); |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 180 | int result = |
| 181 | ioctl(perf_event_fd_, PERF_EVENT_IOC_SET_OUTPUT, event_fd.perf_event_fd_); |
Yabin Cui | 6173592 | 2016-07-08 13:56:48 -0700 | [diff] [blame] | 182 | if (result != 0) { |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 183 | if (report_error) { |
| 184 | PLOG(ERROR) << "failed to share mapped buffer of " |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 185 | << event_fd.perf_event_fd_ << " with " << perf_event_fd_; |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 186 | } |
Yabin Cui | 6173592 | 2016-07-08 13:56:48 -0700 | [diff] [blame] | 187 | return false; |
| 188 | } |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 189 | return true; |
| 190 | } |
| 191 | |
Yabin Cui | 0a072cd | 2016-07-13 17:06:50 -0700 | [diff] [blame] | 192 | void EventFd::DestroyMappedBuffer() { |
| 193 | if (HasMappedBuffer()) { |
| 194 | munmap(mmap_addr_, mmap_len_); |
| 195 | mmap_addr_ = nullptr; |
| 196 | mmap_len_ = 0; |
| 197 | mmap_metadata_page_ = nullptr; |
| 198 | mmap_data_buffer_ = nullptr; |
| 199 | mmap_data_buffer_size_ = 0; |
| 200 | } |
| 201 | } |
| 202 | |
Yabin Cui | 2ea6de1 | 2016-10-24 19:13:09 -0700 | [diff] [blame] | 203 | size_t EventFd::GetAvailableMmapData(std::vector<char>& buffer, size_t& buffer_pos) { |
Yabin Cui | 6173592 | 2016-07-08 13:56:48 -0700 | [diff] [blame] | 204 | if (!HasMappedBuffer()) { |
| 205 | return 0; |
| 206 | } |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 207 | // The mmap_data_buffer is used as a ring buffer between the kernel and |
| 208 | // simpleperf. The kernel continuously writes records to the buffer, and |
| 209 | // simpleperf continuously read records out. |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 210 | // _________________________________________ |
| 211 | // buffer | can write | can read | can write | |
| 212 | // ^ ^ |
| 213 | // read_head write_head |
| 214 | // |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 215 | // So simpleperf can read records in [read_head, write_head), and the kernel |
| 216 | // can write records in [write_head, read_head). The kernel is responsible |
| 217 | // for updating write_head, and simpleperf is responsible for updating |
| 218 | // read_head. |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 219 | |
Yabin Cui | f469c3d | 2015-10-07 15:00:46 -0700 | [diff] [blame] | 220 | size_t buf_mask = mmap_data_buffer_size_ - 1; |
Yabin Cui | dbbda30 | 2016-07-28 12:55:41 -0700 | [diff] [blame] | 221 | size_t write_head = |
| 222 | static_cast<size_t>(mmap_metadata_page_->data_head & buf_mask); |
| 223 | size_t read_head = |
| 224 | static_cast<size_t>(mmap_metadata_page_->data_tail & buf_mask); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 225 | |
| 226 | if (read_head == write_head) { |
| 227 | // No available data. |
| 228 | return 0; |
| 229 | } |
Yabin Cui | 2ea6de1 | 2016-10-24 19:13:09 -0700 | [diff] [blame] | 230 | size_t read_bytes; |
| 231 | if (read_head < write_head) { |
| 232 | read_bytes = write_head - read_head; |
| 233 | } else { |
| 234 | read_bytes = mmap_data_buffer_size_ - read_head + write_head; |
| 235 | } |
| 236 | // Extend the buffer if it is not big enough. |
| 237 | if (buffer.size() < buffer_pos + read_bytes) { |
| 238 | buffer.resize(buffer_pos + read_bytes); |
| 239 | } |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 240 | |
Yabin Cui | 92f80f4 | 2017-01-06 15:01:42 -0800 | [diff] [blame] | 241 | // rmb() used to ensure reading data after reading data_head. |
| 242 | __sync_synchronize(); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 243 | |
Yabin Cui | 2ea6de1 | 2016-10-24 19:13:09 -0700 | [diff] [blame] | 244 | // Copy records from mapped buffer. Note that records can be wrapped at the |
| 245 | // end of the mapped buffer. |
| 246 | char* to = &buffer[buffer_pos]; |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 247 | if (read_head < write_head) { |
Yabin Cui | f469c3d | 2015-10-07 15:00:46 -0700 | [diff] [blame] | 248 | char* from = mmap_data_buffer_ + read_head; |
| 249 | size_t n = write_head - read_head; |
| 250 | memcpy(to, from, n); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 251 | } else { |
Yabin Cui | f469c3d | 2015-10-07 15:00:46 -0700 | [diff] [blame] | 252 | char* from = mmap_data_buffer_ + read_head; |
| 253 | size_t n = mmap_data_buffer_size_ - read_head; |
| 254 | memcpy(to, from, n); |
| 255 | to += n; |
| 256 | from = mmap_data_buffer_; |
| 257 | n = write_head; |
| 258 | memcpy(to, from, n); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 259 | } |
Yabin Cui | 2ea6de1 | 2016-10-24 19:13:09 -0700 | [diff] [blame] | 260 | buffer_pos += read_bytes; |
Yabin Cui | f469c3d | 2015-10-07 15:00:46 -0700 | [diff] [blame] | 261 | DiscardMmapData(read_bytes); |
| 262 | return read_bytes; |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 263 | } |
| 264 | |
| 265 | void EventFd::DiscardMmapData(size_t discard_size) { |
Yabin Cui | 92f80f4 | 2017-01-06 15:01:42 -0800 | [diff] [blame] | 266 | // mb() used to ensure finish reading data before writing data_tail. |
| 267 | __sync_synchronize(); |
Yabin Cui | 9759e1b | 2015-04-28 15:54:13 -0700 | [diff] [blame] | 268 | mmap_metadata_page_->data_tail += discard_size; |
| 269 | } |
| 270 | |
Yabin Cui | 825e56b | 2016-08-26 18:25:21 -0700 | [diff] [blame] | 271 | bool EventFd::StartPolling(IOEventLoop& loop, |
| 272 | const std::function<bool()>& callback) { |
| 273 | ioevent_ref_ = loop.AddReadEvent(perf_event_fd_, callback); |
| 274 | return ioevent_ref_ != nullptr; |
| 275 | } |
| 276 | |
| 277 | bool EventFd::StopPolling() { return IOEventLoop::DelEvent(ioevent_ref_); } |
| 278 | |
Yabin Cui | 26968e6 | 2017-01-30 11:34:24 -0800 | [diff] [blame] | 279 | bool IsEventAttrSupported(const perf_event_attr& attr) { |
| 280 | if (attr.type == SIMPLEPERF_TYPE_USER_SPACE_SAMPLERS && |
| 281 | attr.config == SIMPLEPERF_CONFIG_INPLACE_SAMPLER) { |
| 282 | // User space samplers don't need kernel support. |
| 283 | return true; |
| 284 | } |
| 285 | std::unique_ptr<EventFd> event_fd = EventFd::OpenEventFile(attr, getpid(), -1, nullptr, false); |
Yabin Cui | 9fd3cc1 | 2015-06-25 17:42:23 -0700 | [diff] [blame] | 286 | return event_fd != nullptr; |
| 287 | } |