From: Prasad Pandit <p...@fedoraproject.org> Libaio defines IO_CMD_FDSYNC command to sync all outstanding asynchronous I/O operations, by flushing out file data to the disk storage.
Enable linux-aio to submit such aio request. This helps to reduce latency induced via pthread_create calls by thread-pool (aio=threads). Signed-off-by: Prasad Pandit <p...@fedoraproject.org> --- block/file-posix.c | 7 +++++++ block/linux-aio.c | 22 +++++++++++++++++++++- 2 files changed, 28 insertions(+), 1 deletion(-) v3: check if host kernel supports aio_fsync call -> https://lists.nongnu.org/archive/html/qemu-devel/2024-03/msg03210.html diff --git a/block/file-posix.c b/block/file-posix.c index 35684f7e21..a30494d1a8 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2453,6 +2453,8 @@ static inline bool raw_check_linux_io_uring(BDRVRawState *s) #endif #ifdef CONFIG_LINUX_AIO +extern bool laio_has_fdsync(int); + static inline bool raw_check_linux_aio(BDRVRawState *s) { Error *local_err = NULL; @@ -2599,6 +2601,11 @@ static int coroutine_fn raw_co_flush_to_disk(BlockDriverState *bs) if (raw_check_linux_io_uring(s)) { return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH); } +#endif +#ifdef CONFIG_LINUX_AIO + if (raw_check_linux_aio(s) && laio_has_fdsync(s->fd)) { + return laio_co_submit(s->fd, 0, NULL, QEMU_AIO_FLUSH, 0); + } #endif return raw_thread_pool_submit(handle_aiocb_flush, &acb); } diff --git a/block/linux-aio.c b/block/linux-aio.c index ec05d946f3..ed20a503e9 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -67,6 +67,7 @@ struct LinuxAioState { int event_max; }; +bool laio_has_fdsync(int); static void ioq_submit(LinuxAioState *s); static inline ssize_t io_event_ret(struct io_event *ev) @@ -384,6 +385,9 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset, case QEMU_AIO_READ: io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); break; + case QEMU_AIO_FLUSH: + io_prep_fdsync(iocbs, fd); + break; /* Currently Linux kernel does not support other operations */ default: fprintf(stderr, "%s: invalid AIO request type 0x%x.\n", @@ -412,7 +416,7 @@ int coroutine_fn laio_co_submit(int fd, uint64_t offset, QEMUIOVector *qiov, AioContext *ctx = qemu_get_current_aio_context(); struct qemu_laiocb laiocb = { .co = qemu_coroutine_self(), - .nbytes = qiov->size, + .nbytes = qiov ? qiov->size : 0, .ctx = aio_get_linux_aio(ctx), .ret = -EINPROGRESS, .is_read = (type == QEMU_AIO_READ), @@ -486,3 +490,19 @@ void laio_cleanup(LinuxAioState *s) } g_free(s); } + +bool laio_has_fdsync(int fd) +{ + struct iocb cb; + struct iocb *cbs[] = {&cb, NULL}; + + io_context_t ctx = 0; + io_setup(1, &ctx); + + /* check if host kernel supports IO_CMD_FDSYNC */ + io_prep_fdsync(&cb, fd); + int ret = io_submit(ctx, 1, cbs); + + io_destroy(ctx); + return (ret == -EINVAL) ? false : true; +} -- 2.44.0
