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DiskPool.h
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DiskPool.h
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//
// Created by Agustin Gianni on 11/18/16.
//
#ifndef THREADPROFILER_DISKPOOL_H
#define THREADPROFILER_DISKPOOL_H
#include <atomic>
#include <mutex>
#include <cstddef>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <cerrno>
#include <iostream>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
constexpr size_t KB(size_t size) { return size * 1024; }
constexpr size_t MB(size_t size) { return KB(size) * 1024; }
constexpr size_t GB(size_t size) { return MB(size) * 1024; }
// Implement a memory map policy using 'mmap'.
struct mmap_policy {
static void *load(const char *filename, size_t size) {
auto fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0644);
if (fd == -1) {
std::cerr << "Failed to open file: " << strerror(errno) << std::endl;
abort();
}
if (ftruncate(fd, size) == -1) {
close(fd);
std::cerr << "Failed to ftruncate file: " << strerror(errno) << std::endl;
abort();
}
auto address = reinterpret_cast<uint8_t *>(mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 0));
if (address == MAP_FAILED) {
close(fd);
std::cerr << "Failed to map file: " << strerror(errno) << std::endl;
abort();
}
if (close(fd) != 0) {
unload(address, size);
std::cerr << "Failed to close file: " << strerror(errno) << std::endl;
abort();
}
return address;
}
static void unload(void *address, size_t size) {
if (munmap(address, size) != 0) {
std::cerr << "Failed to unmap file: " << strerror(errno) << std::endl;
abort();
}
}
static void flush(void *address, size_t size) {
if (madvise(address, size, MADV_DONTNEED)) {
std::cerr << "Failed to flush memory: " << strerror(errno) << std::endl;
abort();
}
}
};
// Simple implementation of a spin lock.
class SpinLock {
public:
void lock() {
while(m_lock.test_and_set(std::memory_order_acquire)) {
}
}
void unlock() {
m_lock.clear(std::memory_order_release);
}
private:
std::atomic_flag m_lock = ATOMIC_FLAG_INIT;
};
// Implement a policy that increments the value non atomically.
template <typename T = size_t> class RawIncrement {
private:
T m_top{0};
public:
T increment(T size) {
auto tmp = m_top;
m_top += size;
return m_top;
}
};
// Implement a policy that uses std::atomic to increment the value.
template <typename T = size_t> class AtomicIncrement {
private:
std::atomic<T> m_top{0};
public:
T increment(T size) {
return m_top.fetch_add(size, std::memory_order_relaxed);
}
};
// Implement a policy that uses std::mutex to increment the value.
template <typename T = size_t> class LockedIncrement {
private:
std::mutex m_mutex;
T m_top{0};
public:
T increment(T size) {
std::lock_guard<std::mutex> lock(m_mutex);
auto tmp = m_top;
m_top += size;
return tmp;
}
};
// Implement a policy that uses SpinLock to increment the value.
template <typename T = size_t> class SpinLockIncrement {
private:
SpinLock m_spinlock;
T m_top{0};
public:
T increment(T size) {
m_spinlock.lock();
auto tmp = m_top;
m_top += size;
m_spinlock.unlock();
return tmp;
}
};
// A 'DiskPool' is a named file backed memory allocator.
template<typename IncrementPolicy = AtomicIncrement<size_t>, typename FileMapPolicy = mmap_policy>
class DiskPool: public IncrementPolicy {
protected:
uint8_t *m_address;
size_t m_size;
public:
DiskPool(const char *filename, size_t size) : m_size{size} {
m_address = static_cast<uint8_t *>(FileMapPolicy::load(filename, m_size));
}
~DiskPool() {
FileMapPolicy::unload(m_address, m_size);
}
uint8_t *alloc(size_t size) {
return m_address + IncrementPolicy::increment(size);
}
void flush() const {
FileMapPolicy::flush(m_address, m_size);
}
private:
// Avoid moves and copies.
DiskPool(const DiskPool &) = delete;
DiskPool &operator=(const DiskPool &) = delete;
DiskPool(DiskPool &&) = delete;
DiskPool &operator=(DiskPool &&) = delete;
};
// Define basic DiskPool implementations to be used by the client.
using DiskPoolRaw = DiskPool<RawIncrement<size_t>>;
using DiskPoolAtomic = DiskPool<AtomicIncrement<size_t>>;
using DiskPoolLock = DiskPool<LockedIncrement<size_t>>;
using DiskPoolSpinLock = DiskPool<SpinLockIncrement<size_t>>;
#endif //THREADPROFILER_DISKPOOL_H