189 lines
6.2 KiB
C++
189 lines
6.2 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "event_fd.h"
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#include <fcntl.h>
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#include <poll.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h>
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#include <sys/syscall.h>
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#include <sys/types.h>
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#include <atomic>
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#include <memory>
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#include <android-base/file.h>
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#include <android-base/logging.h>
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#include <android-base/stringprintf.h>
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#include "event_type.h"
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#include "perf_event.h"
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#include "utils.h"
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std::vector<char> EventFd::data_process_buffer_;
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static int perf_event_open(perf_event_attr* attr, pid_t pid, int cpu, int group_fd,
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unsigned long flags) {
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return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
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}
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std::unique_ptr<EventFd> EventFd::OpenEventFile(const perf_event_attr& attr, pid_t tid, int cpu,
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bool report_error) {
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perf_event_attr perf_attr = attr;
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std::string event_name = "unknown event";
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const EventType* event_type = FindEventTypeByConfig(perf_attr.type, perf_attr.config);
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if (event_type != nullptr) {
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event_name = event_type->name;
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}
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int perf_event_fd = perf_event_open(&perf_attr, tid, cpu, -1, 0);
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if (perf_event_fd == -1) {
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if (report_error) {
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PLOG(ERROR) << "open perf_event_file (event " << event_name << ", tid " << tid << ", cpu "
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<< cpu << ") failed";
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} else {
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PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", tid " << tid << ", cpu "
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<< cpu << ") failed";
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}
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return nullptr;
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}
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if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) {
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if (report_error) {
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PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " << event_name << ", tid "
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<< tid << ", cpu " << cpu << ") failed";
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} else {
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PLOG(DEBUG) << "fcntl(FD_CLOEXEC) for perf_event_file (event " << event_name << ", tid "
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<< tid << ", cpu " << cpu << ") failed";
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}
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return nullptr;
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}
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return std::unique_ptr<EventFd>(new EventFd(perf_event_fd, event_name, tid, cpu));
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}
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EventFd::~EventFd() {
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if (mmap_addr_ != nullptr) {
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munmap(mmap_addr_, mmap_len_);
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}
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close(perf_event_fd_);
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}
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std::string EventFd::Name() const {
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return android::base::StringPrintf("perf_event_file(event %s, tid %d, cpu %d)",
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event_name_.c_str(), tid_, cpu_);
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}
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uint64_t EventFd::Id() const {
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if (id_ == 0) {
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PerfCounter counter;
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if (ReadCounter(&counter)) {
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id_ = counter.id;
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}
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}
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return id_;
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}
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bool EventFd::ReadCounter(PerfCounter* counter) const {
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CHECK(counter != nullptr);
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if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) {
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PLOG(ERROR) << "ReadCounter from " << Name() << " failed";
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return false;
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}
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return true;
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}
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bool EventFd::MmapContent(size_t mmap_pages) {
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CHECK(IsPowerOfTwo(mmap_pages));
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size_t page_size = sysconf(_SC_PAGE_SIZE);
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size_t mmap_len = (mmap_pages + 1) * page_size;
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void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, perf_event_fd_, 0);
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if (mmap_addr == MAP_FAILED) {
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PLOG(ERROR) << "mmap() failed for " << Name();
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return false;
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}
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mmap_addr_ = mmap_addr;
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mmap_len_ = mmap_len;
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mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_);
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mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size;
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mmap_data_buffer_size_ = mmap_len_ - page_size;
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if (data_process_buffer_.size() < mmap_data_buffer_size_) {
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data_process_buffer_.resize(mmap_data_buffer_size_);
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}
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return true;
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}
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size_t EventFd::GetAvailableMmapData(char** pdata) {
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// The mmap_data_buffer is used as a ring buffer like below. The kernel continuously writes
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// records to the buffer, and the user continuously read records out.
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// _________________________________________
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// buffer | can write | can read | can write |
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// ^ ^
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// read_head write_head
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//
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// So the user can read records in [read_head, write_head), and the kernel can write records
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// in [write_head, read_head). The kernel is responsible for updating write_head, and the user
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// is responsible for updating read_head.
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size_t buf_mask = mmap_data_buffer_size_ - 1;
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size_t write_head = static_cast<size_t>(mmap_metadata_page_->data_head & buf_mask);
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size_t read_head = static_cast<size_t>(mmap_metadata_page_->data_tail & buf_mask);
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if (read_head == write_head) {
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// No available data.
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return 0;
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}
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// Make sure we can see the data after the fence.
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std::atomic_thread_fence(std::memory_order_acquire);
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// Copy records from mapped buffer to data_process_buffer. Note that records can be wrapped
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// at the end of the mapped buffer.
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char* to = data_process_buffer_.data();
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if (read_head < write_head) {
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char* from = mmap_data_buffer_ + read_head;
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size_t n = write_head - read_head;
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memcpy(to, from, n);
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to += n;
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} else {
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char* from = mmap_data_buffer_ + read_head;
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size_t n = mmap_data_buffer_size_ - read_head;
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memcpy(to, from, n);
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to += n;
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from = mmap_data_buffer_;
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n = write_head;
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memcpy(to, from, n);
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to += n;
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}
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size_t read_bytes = to - data_process_buffer_.data();
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*pdata = data_process_buffer_.data();
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DiscardMmapData(read_bytes);
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return read_bytes;
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}
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void EventFd::DiscardMmapData(size_t discard_size) {
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mmap_metadata_page_->data_tail += discard_size;
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}
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void EventFd::PreparePollForMmapData(pollfd* poll_fd) {
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memset(poll_fd, 0, sizeof(pollfd));
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poll_fd->fd = perf_event_fd_;
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poll_fd->events = POLLIN;
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}
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bool IsEventAttrSupportedByKernel(perf_event_attr attr) {
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auto event_fd = EventFd::OpenEventFile(attr, getpid(), -1, false);
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return event_fd != nullptr;
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}
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