Range<AsyncIO::Op**> AsyncIO::doWait(size_t minRequests, size_t maxRequests) {
io_event events[pending_];
int count;
do {
// Wait forever
count = io_getevents(ctx_, minRequests, maxRequests, events, nullptr);
} while (count == -EINTR);
checkKernelError(count, "AsyncIO: io_getevents failed");
DCHECK_GE(count, minRequests); // the man page says so
DCHECK_LE(count, pending_);
completed_.clear();
if (count == 0) {
return folly::Range<Op**>();
}
for (size_t i = 0; i < count; ++i) {
DCHECK(events[i].obj);
Op* op = boost::intrusive::get_parent_from_member(
events[i].obj, &AsyncIOOp::iocb_);
--pending_;
op->complete(events[i].res);
completed_.push_back(op);
}
return folly::Range<Op**>(&completed_.front(), count);
}
void AsyncIO::initializeContext() {
if (!ctxSet_.load(std::memory_order_acquire)) {
std::lock_guard<std::mutex> lock(initMutex_);
if (!ctxSet_.load(std::memory_order_relaxed)) {
int rc = io_queue_init(capacity_, &ctx_);
// returns negative errno
if (rc == -EAGAIN) {
long aio_nr, aio_max;
std::unique_ptr<FILE, int(*)(FILE*)>
fp(fopen("/proc/sys/fs/aio-nr", "r"), fclose);
PCHECK(fp);
CHECK_EQ(fscanf(fp.get(), "%ld", &aio_nr), 1);
std::unique_ptr<FILE, int(*)(FILE*)>
aio_max_fp(fopen("/proc/sys/fs/aio-max-nr", "r"), fclose);
PCHECK(aio_max_fp);
CHECK_EQ(fscanf(aio_max_fp.get(), "%ld", &aio_max), 1);
LOG(ERROR) << "No resources for requested capacity of " << capacity_;
LOG(ERROR) << "aio_nr " << aio_nr << ", aio_max_nr " << aio_max;
}
checkKernelError(rc, "AsyncIO: io_queue_init failed");
DCHECK(ctx_);
ctxSet_.store(true, std::memory_order_release);
}
}
}
void AsyncIO::initializeContext() {
if (!ctx_) {
int rc = io_queue_init(capacity_, &ctx_);
// returns negative errno
checkKernelError(rc, "AsyncIO: io_queue_init failed");
DCHECK(ctx_);
}
}
void AsyncIO::submit(Op* op) {
CHECK_EQ(op->state(), Op::State::INITIALIZED);
CHECK_LT(pending_, capacity_) << "too many pending requests";
initializeContext(); // on demand
iocb* cb = &op->iocb_;
cb->data = nullptr; // unused
if (pollFd_ != -1) {
io_set_eventfd(cb, pollFd_);
}
int rc = io_submit(ctx_, 1, &cb);
checkKernelError(rc, "AsyncIO: io_submit failed");
DCHECK_EQ(rc, 1);
op->start();
++pending_;
}
