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rocksdb/util/env_posix.cc

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "posix/io_posix.h"
// Get nano time includes
#if defined(OS_LINUX) || defined(OS_FREEBSD)
#elif defined(__MACH__)
#include <mach/clock.h>
#include <mach/mach.h>
#else
#include <chrono>
#endif
#if !defined(TMPFS_MAGIC)
#define TMPFS_MAGIC 0x01021994
#endif
#if !defined(XFS_SUPER_MAGIC)
#define XFS_SUPER_MAGIC 0x58465342
#endif
#if !defined(EXT4_SUPER_MAGIC)
#define EXT4_SUPER_MAGIC 0xEF53
#endif
namespace rocksdb {
namespace {
ThreadStatusUpdater* CreateThreadStatusUpdater() {
return new ThreadStatusUpdater();
}
// list of pathnames that are locked
static std::set<std::string> lockedFiles;
static port::Mutex mutex_lockedFiles;
static int LockOrUnlock(const std::string& fname, int fd, bool lock) {
mutex_lockedFiles.Lock();
if (lock) {
// If it already exists in the lockedFiles set, then it is already locked,
// and fail this lock attempt. Otherwise, insert it into lockedFiles.
// This check is needed because fcntl() does not detect lock conflict
// if the fcntl is issued by the same thread that earlier acquired
// this lock.
if (lockedFiles.insert(fname).second == false) {
mutex_lockedFiles.Unlock();
errno = ENOLCK;
return -1;
}
} else {
// If we are unlocking, then verify that we had locked it earlier,
// it should already exist in lockedFiles. Remove it from lockedFiles.
if (lockedFiles.erase(fname) != 1) {
mutex_lockedFiles.Unlock();
errno = ENOLCK;
return -1;
}
}
errno = 0;
struct flock f;
memset(&f, 0, sizeof(f));
f.l_type = (lock ? F_WRLCK : F_UNLCK);
f.l_whence = SEEK_SET;
f.l_start = 0;
f.l_len = 0; // Lock/unlock entire file
int value = fcntl(fd, F_SETLK, &f);
if (value == -1 && lock) {
// if there is an error in locking, then remove the pathname from lockedfiles
lockedFiles.erase(fname);
}
mutex_lockedFiles.Unlock();
return value;
}
void PthreadCall(const char* label, int result) {
if (result != 0) {
fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
abort();
}
}
class PosixFileLock : public FileLock {
public:
int fd_;
std::string filename;
};
class PosixEnv : public Env {
public:
PosixEnv();
virtual ~PosixEnv() {
for (const auto tid : threads_to_join_) {
pthread_join(tid, nullptr);
}
for (int pool_id = 0; pool_id < Env::Priority::TOTAL; ++pool_id) {
thread_pools_[pool_id].JoinAllThreads();
}
// All threads must be joined before the deletion of
// thread_status_updater_.
delete thread_status_updater_;
}
void SetFD_CLOEXEC(int fd, const EnvOptions* options) {
if ((options == nullptr || options->set_fd_cloexec) && fd > 0) {
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
}
}
virtual Status NewSequentialFile(const std::string& fname,
unique_ptr<SequentialFile>* result,
const EnvOptions& options) override {
result->reset();
FILE* f = nullptr;
do {
IOSTATS_TIMER_GUARD(open_nanos);
f = fopen(fname.c_str(), "r");
} while (f == nullptr && errno == EINTR);
if (f == nullptr) {
*result = nullptr;
return IOError(fname, errno);
} else {
int fd = fileno(f);
SetFD_CLOEXEC(fd, &options);
result->reset(new PosixSequentialFile(fname, f, options));
return Status::OK();
}
}
virtual Status NewRandomAccessFile(const std::string& fname,
unique_ptr<RandomAccessFile>* result,
const EnvOptions& options) override {
result->reset();
Status s;
int fd;
{
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(fname.c_str(), O_RDONLY);
}
SetFD_CLOEXEC(fd, &options);
if (fd < 0) {
s = IOError(fname, errno);
} else if (options.use_mmap_reads && sizeof(void*) >= 8) {
// Use of mmap for random reads has been removed because it
// kills performance when storage is fast.
// Use mmap when virtual address-space is plentiful.
uint64_t size;
s = GetFileSize(fname, &size);
if (s.ok()) {
void* base = mmap(nullptr, size, PROT_READ, MAP_SHARED, fd, 0);
if (base != MAP_FAILED) {
result->reset(new PosixMmapReadableFile(fd, fname, base,
size, options));
} else {
s = IOError(fname, errno);
}
}
close(fd);
} else {
result->reset(new PosixRandomAccessFile(fname, fd, options));
}
return s;
}
virtual Status NewWritableFile(const std::string& fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options) override {
result->reset();
Status s;
int fd = -1;
do {
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(fname.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
} while (fd < 0 && errno == EINTR);
if (fd < 0) {
s = IOError(fname, errno);
} else {
SetFD_CLOEXEC(fd, &options);
if (options.use_mmap_writes) {
if (!checkedDiskForMmap_) {
// this will be executed once in the program's lifetime.
// do not use mmapWrite on non ext-3/xfs/tmpfs systems.
if (!SupportsFastAllocate(fname)) {
forceMmapOff = true;
}
checkedDiskForMmap_ = true;
}
}
if (options.use_mmap_writes && !forceMmapOff) {
result->reset(new PosixMmapFile(fname, fd, page_size_, options));
} else {
// disable mmap writes
EnvOptions no_mmap_writes_options = options;
no_mmap_writes_options.use_mmap_writes = false;
result->reset(new PosixWritableFile(fname, fd, no_mmap_writes_options));
}
}
return s;
}
virtual Status ReuseWritableFile(const std::string& fname,
const std::string& old_fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options) override {
result->reset();
Status s;
int fd = -1;
do {
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(old_fname.c_str(), O_RDWR, 0644);
} while (fd < 0 && errno == EINTR);
if (fd < 0) {
s = IOError(fname, errno);
} else {
SetFD_CLOEXEC(fd, &options);
// rename into place
if (rename(old_fname.c_str(), fname.c_str()) != 0) {
Status r = IOError(old_fname, errno);
close(fd);
return r;
}
if (options.use_mmap_writes) {
if (!checkedDiskForMmap_) {
// this will be executed once in the program's lifetime.
// do not use mmapWrite on non ext-3/xfs/tmpfs systems.
if (!SupportsFastAllocate(fname)) {
forceMmapOff = true;
}
checkedDiskForMmap_ = true;
}
}
if (options.use_mmap_writes && !forceMmapOff) {
result->reset(new PosixMmapFile(fname, fd, page_size_, options));
} else {
// disable mmap writes
EnvOptions no_mmap_writes_options = options;
no_mmap_writes_options.use_mmap_writes = false;
result->reset(new PosixWritableFile(fname, fd, no_mmap_writes_options));
}
}
return s;
}
virtual Status NewDirectory(const std::string& name,
unique_ptr<Directory>* result) override {
result->reset();
int fd;
{
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(name.c_str(), 0);
}
if (fd < 0) {
return IOError(name, errno);
} else {
result->reset(new PosixDirectory(fd));
}
return Status::OK();
}
virtual Status FileExists(const std::string& fname) override {
int result = access(fname.c_str(), F_OK);
if (result == 0) {
return Status::OK();
}
switch (errno) {
case EACCES:
case ELOOP:
case ENAMETOOLONG:
case ENOENT:
case ENOTDIR:
return Status::NotFound();
default:
assert(result == EIO || result == ENOMEM);
return Status::IOError("Unexpected error(" + ToString(result) +
") accessing file `" + fname + "' ");
}
}
virtual Status GetChildren(const std::string& dir,
std::vector<std::string>* result) override {
result->clear();
DIR* d = opendir(dir.c_str());
if (d == nullptr) {
return IOError(dir, errno);
}
struct dirent* entry;
while ((entry = readdir(d)) != nullptr) {
result->push_back(entry->d_name);
}
closedir(d);
return Status::OK();
}
virtual Status DeleteFile(const std::string& fname) override {
Status result;
if (unlink(fname.c_str()) != 0) {
result = IOError(fname, errno);
}
return result;
};
virtual Status CreateDir(const std::string& name) override {
Status result;
if (mkdir(name.c_str(), 0755) != 0) {
result = IOError(name, errno);
}
return result;
};
virtual Status CreateDirIfMissing(const std::string& name) override {
Status result;
if (mkdir(name.c_str(), 0755) != 0) {
if (errno != EEXIST) {
result = IOError(name, errno);
} else if (!DirExists(name)) { // Check that name is actually a
// directory.
// Message is taken from mkdir
result = Status::IOError("`"+name+"' exists but is not a directory");
}
}
return result;
};
virtual Status DeleteDir(const std::string& name) override {
Status result;
if (rmdir(name.c_str()) != 0) {
result = IOError(name, errno);
}
return result;
};
virtual Status GetFileSize(const std::string& fname,
uint64_t* size) override {
Status s;
struct stat sbuf;
if (stat(fname.c_str(), &sbuf) != 0) {
*size = 0;
s = IOError(fname, errno);
} else {
*size = sbuf.st_size;
}
return s;
}
virtual Status GetFileModificationTime(const std::string& fname,
uint64_t* file_mtime) override {
struct stat s;
if (stat(fname.c_str(), &s) !=0) {
return IOError(fname, errno);
}
*file_mtime = static_cast<uint64_t>(s.st_mtime);
return Status::OK();
}
virtual Status RenameFile(const std::string& src,
const std::string& target) override {
Status result;
if (rename(src.c_str(), target.c_str()) != 0) {
result = IOError(src, errno);
}
return result;
}
virtual Status LinkFile(const std::string& src,
const std::string& target) override {
Status result;
if (link(src.c_str(), target.c_str()) != 0) {
if (errno == EXDEV) {
return Status::NotSupported("No cross FS links allowed");
}
result = IOError(src, errno);
}
return result;
}
virtual Status LockFile(const std::string& fname, FileLock** lock) override {
*lock = nullptr;
Status result;
int fd;
{
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(fname.c_str(), O_RDWR | O_CREAT, 0644);
}
if (fd < 0) {
result = IOError(fname, errno);
} else if (LockOrUnlock(fname, fd, true) == -1) {
result = IOError("lock " + fname, errno);
close(fd);
} else {
SetFD_CLOEXEC(fd, nullptr);
PosixFileLock* my_lock = new PosixFileLock;
my_lock->fd_ = fd;
my_lock->filename = fname;
*lock = my_lock;
}
return result;
}
virtual Status UnlockFile(FileLock* lock) override {
PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
Status result;
if (LockOrUnlock(my_lock->filename, my_lock->fd_, false) == -1) {
result = IOError("unlock", errno);
}
close(my_lock->fd_);
delete my_lock;
return result;
}
virtual void Schedule(void (*function)(void* arg1), void* arg,
Priority pri = LOW, void* tag = nullptr) override;
virtual int UnSchedule(void* arg, Priority pri) override;
virtual void StartThread(void (*function)(void* arg), void* arg) override;
virtual void WaitForJoin() override;
virtual unsigned int GetThreadPoolQueueLen(Priority pri = LOW) const override;
virtual Status GetTestDirectory(std::string* result) override {
const char* env = getenv("TEST_TMPDIR");
if (env && env[0] != '\0') {
*result = env;
} else {
char buf[100];
snprintf(buf, sizeof(buf), "/tmp/rocksdbtest-%d", int(geteuid()));
*result = buf;
}
// Directory may already exist
CreateDir(*result);
return Status::OK();
}
virtual Status GetThreadList(
std::vector<ThreadStatus>* thread_list) override {
assert(thread_status_updater_);
return thread_status_updater_->GetThreadList(thread_list);
}
static uint64_t gettid(pthread_t tid) {
uint64_t thread_id = 0;
memcpy(&thread_id, &tid, std::min(sizeof(thread_id), sizeof(tid)));
return thread_id;
}
static uint64_t gettid() {
pthread_t tid = pthread_self();
return gettid(tid);
}
virtual uint64_t GetThreadID() const override {
return gettid(pthread_self());
}
virtual Status NewLogger(const std::string& fname,
shared_ptr<Logger>* result) override {
FILE* f;
{
IOSTATS_TIMER_GUARD(open_nanos);
f = fopen(fname.c_str(), "w");
}
if (f == nullptr) {
result->reset();
return IOError(fname, errno);
} else {
int fd = fileno(f);
#ifdef ROCKSDB_FALLOCATE_PRESENT
fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 4 * 1024);
#endif
SetFD_CLOEXEC(fd, nullptr);
result->reset(new PosixLogger(f, &PosixEnv::gettid, this));
return Status::OK();
}
}
virtual uint64_t NowMicros() override {
struct timeval tv;
gettimeofday(&tv, nullptr);
return static_cast<uint64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
}
virtual uint64_t NowNanos() override {
#if defined(OS_LINUX) || defined(OS_FREEBSD)
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
#elif defined(__MACH__)
clock_serv_t cclock;
mach_timespec_t ts;
host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
clock_get_time(cclock, &ts);
mach_port_deallocate(mach_task_self(), cclock);
return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
#else
return std::chrono::duration_cast<std::chrono::nanoseconds>(
std::chrono::steady_clock::now().time_since_epoch()).count();
#endif
}
virtual void SleepForMicroseconds(int micros) override { usleep(micros); }
virtual Status GetHostName(char* name, uint64_t len) override {
int ret = gethostname(name, static_cast<size_t>(len));
if (ret < 0) {
if (errno == EFAULT || errno == EINVAL)
return Status::InvalidArgument(strerror(errno));
else
return IOError("GetHostName", errno);
}
return Status::OK();
}
virtual Status GetCurrentTime(int64_t* unix_time) override {
time_t ret = time(nullptr);
if (ret == (time_t) -1) {
return IOError("GetCurrentTime", errno);
}
*unix_time = (int64_t) ret;
return Status::OK();
}
virtual Status GetAbsolutePath(const std::string& db_path,
std::string* output_path) override {
if (db_path.find('/') == 0) {
*output_path = db_path;
return Status::OK();
}
char the_path[256];
char* ret = getcwd(the_path, 256);
if (ret == nullptr) {
return Status::IOError(strerror(errno));
}
*output_path = ret;
return Status::OK();
}
// Allow increasing the number of worker threads.
virtual void SetBackgroundThreads(int num, Priority pri) override {
assert(pri >= Priority::LOW && pri <= Priority::HIGH);
thread_pools_[pri].SetBackgroundThreads(num);
}
// Allow increasing the number of worker threads.
virtual void IncBackgroundThreadsIfNeeded(int num, Priority pri) override {
assert(pri >= Priority::LOW && pri <= Priority::HIGH);
thread_pools_[pri].IncBackgroundThreadsIfNeeded(num);
}
virtual void LowerThreadPoolIOPriority(Priority pool = LOW) override {
assert(pool >= Priority::LOW && pool <= Priority::HIGH);
#ifdef OS_LINUX
thread_pools_[pool].LowerIOPriority();
#endif
}
virtual std::string TimeToString(uint64_t secondsSince1970) override {
const time_t seconds = (time_t)secondsSince1970;
struct tm t;
int maxsize = 64;
std::string dummy;
dummy.reserve(maxsize);
dummy.resize(maxsize);
char* p = &dummy[0];
localtime_r(&seconds, &t);
snprintf(p, maxsize,
"%04d/%02d/%02d-%02d:%02d:%02d ",
t.tm_year + 1900,
t.tm_mon + 1,
t.tm_mday,
t.tm_hour,
t.tm_min,
t.tm_sec);
return dummy;
}
EnvOptions OptimizeForLogWrite(const EnvOptions& env_options,
const DBOptions& db_options) const override {
EnvOptions optimized = env_options;
optimized.use_mmap_writes = false;
optimized.bytes_per_sync = db_options.wal_bytes_per_sync;
// TODO(icanadi) it's faster if fallocate_with_keep_size is false, but it
// breaks TransactionLogIteratorStallAtLastRecord unit test. Fix the unit
// test and make this false
optimized.fallocate_with_keep_size = true;
return optimized;
}
EnvOptions OptimizeForManifestWrite(
const EnvOptions& env_options) const override {
EnvOptions optimized = env_options;
optimized.use_mmap_writes = false;
optimized.fallocate_with_keep_size = true;
return optimized;
}
private:
bool checkedDiskForMmap_;
bool forceMmapOff; // do we override Env options?
// Returns true iff the named directory exists and is a directory.
virtual bool DirExists(const std::string& dname) {
struct stat statbuf;
if (stat(dname.c_str(), &statbuf) == 0) {
return S_ISDIR(statbuf.st_mode);
}
return false; // stat() failed return false
}
bool SupportsFastAllocate(const std::string& path) {
#ifdef ROCKSDB_FALLOCATE_PRESENT
struct statfs s;
if (statfs(path.c_str(), &s)){
return false;
}
switch (s.f_type) {
case EXT4_SUPER_MAGIC:
return true;
case XFS_SUPER_MAGIC:
return true;
case TMPFS_MAGIC:
return true;
default:
return false;
}
#else
return false;
#endif
}
size_t page_size_;
class ThreadPool {
public:
ThreadPool()
: total_threads_limit_(1),
bgthreads_(0),
queue_(),
queue_len_(0),
exit_all_threads_(false),
low_io_priority_(false),
env_(nullptr) {
PthreadCall("mutex_init", pthread_mutex_init(&mu_, nullptr));
PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, nullptr));
}
~ThreadPool() {
assert(bgthreads_.size() == 0U);
}
void JoinAllThreads() {
PthreadCall("lock", pthread_mutex_lock(&mu_));
assert(!exit_all_threads_);
exit_all_threads_ = true;
PthreadCall("signalall", pthread_cond_broadcast(&bgsignal_));
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
for (const auto tid : bgthreads_) {
pthread_join(tid, nullptr);
}
bgthreads_.clear();
}
void SetHostEnv(Env* env) {
env_ = env;
}
void LowerIOPriority() {
#ifdef OS_LINUX
PthreadCall("lock", pthread_mutex_lock(&mu_));
low_io_priority_ = true;
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
#endif
}
// Return true if there is at least one thread needs to terminate.
bool HasExcessiveThread() {
return static_cast<int>(bgthreads_.size()) > total_threads_limit_;
}
// Return true iff the current thread is the excessive thread to terminate.
// Always terminate the running thread that is added last, even if there are
// more than one thread to terminate.
bool IsLastExcessiveThread(size_t thread_id) {
return HasExcessiveThread() && thread_id == bgthreads_.size() - 1;
}
// Is one of the threads to terminate.
bool IsExcessiveThread(size_t thread_id) {
return static_cast<int>(thread_id) >= total_threads_limit_;
}
// Return the thread priority.
// This would allow its member-thread to know its priority.
Env::Priority GetThreadPriority() {
return priority_;
}
// Set the thread priority.
void SetThreadPriority(Env::Priority priority) {
priority_ = priority;
}
void BGThread(size_t thread_id) {
bool low_io_priority = false;
while (true) {
// Wait until there is an item that is ready to run
PthreadCall("lock", pthread_mutex_lock(&mu_));
// Stop waiting if the thread needs to do work or needs to terminate.
while (!exit_all_threads_ && !IsLastExcessiveThread(thread_id) &&
(queue_.empty() || IsExcessiveThread(thread_id))) {
PthreadCall("wait", pthread_cond_wait(&bgsignal_, &mu_));
}
if (exit_all_threads_) { // mechanism to let BG threads exit safely
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
break;
}
if (IsLastExcessiveThread(thread_id)) {
// Current thread is the last generated one and is excessive.
// We always terminate excessive thread in the reverse order of
// generation time.
auto terminating_thread = bgthreads_.back();
pthread_detach(terminating_thread);
bgthreads_.pop_back();
if (HasExcessiveThread()) {
// There is still at least more excessive thread to terminate.
WakeUpAllThreads();
}
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
break;
}
void (*function)(void*) = queue_.front().function;
void* arg = queue_.front().arg;
queue_.pop_front();
queue_len_.store(static_cast<unsigned int>(queue_.size()),
std::memory_order_relaxed);
bool decrease_io_priority = (low_io_priority != low_io_priority_);
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
#ifdef OS_LINUX
if (decrease_io_priority) {
#define IOPRIO_CLASS_SHIFT (13)
#define IOPRIO_PRIO_VALUE(class, data) \
(((class) << IOPRIO_CLASS_SHIFT) | data)
// Put schedule into IOPRIO_CLASS_IDLE class (lowest)
// These system calls only have an effect when used in conjunction
// with an I/O scheduler that supports I/O priorities. As at
// kernel 2.6.17 the only such scheduler is the Completely
// Fair Queuing (CFQ) I/O scheduler.
// To change scheduler:
// echo cfq > /sys/block/<device_name>/queue/schedule
// Tunables to consider:
// /sys/block/<device_name>/queue/slice_idle
// /sys/block/<device_name>/queue/slice_sync
syscall(SYS_ioprio_set,
1, // IOPRIO_WHO_PROCESS
0, // current thread
IOPRIO_PRIO_VALUE(3, 0));
low_io_priority = true;
}
#else
(void)decrease_io_priority; // avoid 'unused variable' error
#endif
(*function)(arg);
}
}
// Helper struct for passing arguments when creating threads.
struct BGThreadMetadata {
ThreadPool* thread_pool_;
size_t thread_id_; // Thread count in the thread.
explicit BGThreadMetadata(ThreadPool* thread_pool, size_t thread_id)
: thread_pool_(thread_pool), thread_id_(thread_id) {}
};
static void* BGThreadWrapper(void* arg) {
BGThreadMetadata* meta = reinterpret_cast<BGThreadMetadata*>(arg);
size_t thread_id = meta->thread_id_;
ThreadPool* tp = meta->thread_pool_;
#if ROCKSDB_USING_THREAD_STATUS
// for thread-status
ThreadStatusUtil::RegisterThread(tp->env_,
(tp->GetThreadPriority() == Env::Priority::HIGH ?
ThreadStatus::HIGH_PRIORITY :
ThreadStatus::LOW_PRIORITY));
#endif
delete meta;
tp->BGThread(thread_id);
#if ROCKSDB_USING_THREAD_STATUS
ThreadStatusUtil::UnregisterThread();
#endif
return nullptr;
}
void WakeUpAllThreads() {
PthreadCall("signalall", pthread_cond_broadcast(&bgsignal_));
}
void SetBackgroundThreadsInternal(int num, bool allow_reduce) {
PthreadCall("lock", pthread_mutex_lock(&mu_));
if (exit_all_threads_) {
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
return;
}
if (num > total_threads_limit_ ||
(num < total_threads_limit_ && allow_reduce)) {
total_threads_limit_ = std::max(1, num);
WakeUpAllThreads();
StartBGThreads();
}
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
}
void IncBackgroundThreadsIfNeeded(int num) {
SetBackgroundThreadsInternal(num, false);
}
void SetBackgroundThreads(int num) {
SetBackgroundThreadsInternal(num, true);
}
void StartBGThreads() {
// Start background thread if necessary
while ((int)bgthreads_.size() < total_threads_limit_) {
pthread_t t;
PthreadCall(
"create thread",
pthread_create(&t, nullptr, &ThreadPool::BGThreadWrapper,
new BGThreadMetadata(this, bgthreads_.size())));
// Set the thread name to aid debugging
#if defined(_GNU_SOURCE) && defined(__GLIBC_PREREQ)
#if __GLIBC_PREREQ(2, 12)
char name_buf[16];
snprintf(name_buf, sizeof name_buf, "rocksdb:bg%" ROCKSDB_PRIszt,
bgthreads_.size());
name_buf[sizeof name_buf - 1] = '\0';
pthread_setname_np(t, name_buf);
#endif
#endif
bgthreads_.push_back(t);
}
}
void Schedule(void (*function)(void* arg1), void* arg, void* tag) {
PthreadCall("lock", pthread_mutex_lock(&mu_));
if (exit_all_threads_) {
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
return;
}
StartBGThreads();
// Add to priority queue
queue_.push_back(BGItem());
queue_.back().function = function;
queue_.back().arg = arg;
queue_.back().tag = tag;
queue_len_.store(static_cast<unsigned int>(queue_.size()),
std::memory_order_relaxed);
if (!HasExcessiveThread()) {
// Wake up at least one waiting thread.
PthreadCall("signal", pthread_cond_signal(&bgsignal_));
} else {
// Need to wake up all threads to make sure the one woken
// up is not the one to terminate.
WakeUpAllThreads();
}
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
}
int UnSchedule(void* arg) {
int count = 0;
PthreadCall("lock", pthread_mutex_lock(&mu_));
// Remove from priority queue
BGQueue::iterator it = queue_.begin();
while (it != queue_.end()) {
if (arg == (*it).tag) {
it = queue_.erase(it);
count++;
} else {
it++;
}
}
queue_len_.store(static_cast<unsigned int>(queue_.size()),
std::memory_order_relaxed);
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
return count;
}
unsigned int GetQueueLen() const {
return queue_len_.load(std::memory_order_relaxed);
}
private:
// Entry per Schedule() call
struct BGItem {
void* arg;
void (*function)(void*);
void* tag;
};
typedef std::deque<BGItem> BGQueue;
pthread_mutex_t mu_;
pthread_cond_t bgsignal_;
int total_threads_limit_;
std::vector<pthread_t> bgthreads_;
BGQueue queue_;
std::atomic_uint queue_len_; // Queue length. Used for stats reporting
bool exit_all_threads_;
bool low_io_priority_;
Env::Priority priority_;
Env* env_;
};
std::vector<ThreadPool> thread_pools_;
pthread_mutex_t mu_;
std::vector<pthread_t> threads_to_join_;
};
PosixEnv::PosixEnv()
: checkedDiskForMmap_(false),
forceMmapOff(false),
page_size_(getpagesize()),
thread_pools_(Priority::TOTAL) {
PthreadCall("mutex_init", pthread_mutex_init(&mu_, nullptr));
for (int pool_id = 0; pool_id < Env::Priority::TOTAL; ++pool_id) {
thread_pools_[pool_id].SetThreadPriority(
static_cast<Env::Priority>(pool_id));
// This allows later initializing the thread-local-env of each thread.
thread_pools_[pool_id].SetHostEnv(this);
}
thread_status_updater_ = CreateThreadStatusUpdater();
}
void PosixEnv::Schedule(void (*function)(void* arg1), void* arg, Priority pri,
void* tag) {
assert(pri >= Priority::LOW && pri <= Priority::HIGH);
thread_pools_[pri].Schedule(function, arg, tag);
}
int PosixEnv::UnSchedule(void* arg, Priority pri) {
return thread_pools_[pri].UnSchedule(arg);
}
unsigned int PosixEnv::GetThreadPoolQueueLen(Priority pri) const {
assert(pri >= Priority::LOW && pri <= Priority::HIGH);
return thread_pools_[pri].GetQueueLen();
}
struct StartThreadState {
void (*user_function)(void*);
void* arg;
};
static void* StartThreadWrapper(void* arg) {
StartThreadState* state = reinterpret_cast<StartThreadState*>(arg);
state->user_function(state->arg);
delete state;
return nullptr;
}
void PosixEnv::StartThread(void (*function)(void* arg), void* arg) {
pthread_t t;
StartThreadState* state = new StartThreadState;
state->user_function = function;
state->arg = arg;
PthreadCall("start thread",
pthread_create(&t, nullptr, &StartThreadWrapper, state));
PthreadCall("lock", pthread_mutex_lock(&mu_));
threads_to_join_.push_back(t);
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
}
void PosixEnv::WaitForJoin() {
for (const auto tid : threads_to_join_) {
pthread_join(tid, nullptr);
}
threads_to_join_.clear();
}
} // namespace
std::string Env::GenerateUniqueId() {
std::string uuid_file = "/proc/sys/kernel/random/uuid";
Status s = FileExists(uuid_file);
if (s.ok()) {
std::string uuid;
s = ReadFileToString(this, uuid_file, &uuid);
if (s.ok()) {
return uuid;
}
}
// Could not read uuid_file - generate uuid using "nanos-random"
Random64 r(time(nullptr));
uint64_t random_uuid_portion =
r.Uniform(std::numeric_limits<uint64_t>::max());
uint64_t nanos_uuid_portion = NowNanos();
char uuid2[200];
snprintf(uuid2,
200,
"%lx-%lx",
(unsigned long)nanos_uuid_portion,
(unsigned long)random_uuid_portion);
return uuid2;
}
Env* Env::Default() {
static PosixEnv default_env;
return &default_env;
}
} // namespace rocksdb
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