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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.
*/
#ifndef SIMPLE_PERF_EVENT_FD_H_
#define SIMPLE_PERF_EVENT_FD_H_
#include <sys/types.h>
#include <memory>
#include <string>
#include <vector>
#include <android-base/macros.h>
#include "perf_event.h"
struct PerfCounter {
uint64_t value; // The value of the event specified by the perf_event_file.
uint64_t time_enabled; // The enabled time.
uint64_t time_running; // The running time.
uint64_t id; // The id of the perf_event_file.
};
struct pollfd;
// EventFd represents an opened perf_event_file.
class EventFd {
public:
static std::unique_ptr<EventFd> OpenEventFile(const perf_event_attr& attr, pid_t tid, int cpu,
EventFd* group_event_fd, bool report_error = true);
~EventFd();
// Give information about this perf_event_file, like (event_name, tid, cpu).
std::string Name() const;
uint64_t Id() const;
pid_t ThreadId() const {
return tid_;
}
int Cpu() const {
return cpu_;
}
// It tells the kernel to start counting and recording events specified by this file.
bool EnableEvent();
bool ReadCounter(PerfCounter* counter) const;
// Create mapped buffer used to receive records sent by the kernel.
// mmap_pages should be power of 2. If created successfully, fill pollfd,
// which is used to poll() on available mapped data.
bool CreateMappedBuffer(size_t mmap_pages, pollfd* poll_fd);
// Share the mapped buffer used by event_fd. The two EventFds should monitor
// the same event on the same cpu, but have different thread ids.
bool ShareMappedBuffer(const EventFd& event_fd);
bool HasMappedBuffer() const {
return mmap_data_buffer_size_ != 0;
}
// When the kernel writes new sampled records to the mapped area, we can get them by returning
// the start address and size of the data.
size_t GetAvailableMmapData(char** pdata);
private:
EventFd(int perf_event_fd, const std::string& event_name, pid_t tid, int cpu)
: perf_event_fd_(perf_event_fd),
id_(0),
event_name_(event_name),
tid_(tid),
cpu_(cpu),
mmap_addr_(nullptr),
mmap_len_(0),
mmap_metadata_page_(nullptr),
mmap_data_buffer_(nullptr),
mmap_data_buffer_size_(0) {
}
// Discard how much data we have read, so the kernel can reuse this part of mapped area to store
// new data.
void DiscardMmapData(size_t discard_size);
int perf_event_fd_;
mutable uint64_t id_;
const std::string event_name_;
pid_t tid_;
int cpu_;
void* mmap_addr_;
size_t mmap_len_;
perf_event_mmap_page* mmap_metadata_page_; // The first page of mmap_area.
char* mmap_data_buffer_; // Starts from the second page of mmap_area, containing records written
// by then kernel.
size_t mmap_data_buffer_size_;
// As mmap_data_buffer is a ring buffer, it is possible that one record is wrapped at the
// end of the buffer. So we need to copy records from mmap_data_buffer to data_process_buffer
// before processing them.
static std::vector<char> data_process_buffer_;
DISALLOW_COPY_AND_ASSIGN(EventFd);
};
bool IsEventAttrSupportedByKernel(perf_event_attr attr);
#endif // SIMPLE_PERF_EVENT_FD_H_
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