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