libaio engine: print warning for depth > 1 and buffered IO

Linux aio doesn't support queued buffered IO, it has to be
O_DIRECT. So print a warning to that effect, so that users
of fio don't get bad results by mistake.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/engines/libaio.c b/engines/libaio.c
index 871c5a4785d727a72471499ffca93344ff660b1c..f8990c1601ba801309d69e7ef84ceb7bfbfcd71c 100644 (file)
--- a/engines/libaio.c
+++ b/engines/libaio.c
@@ -189,8 +189,14 @@ static void fio_libaio_cleanup(struct thread_data *td)
 static int fio_libaio_init(struct thread_data *td)
 {
        struct libaio_data *ld = malloc(sizeof(*ld));
+       static int warn_print;
        int err;
 
+       if (td->o.iodepth > 1 && !td->o.odirect && !warn_print) {
+               log_info("fio: libaio engine is only async for non-buffered IO\n");
+               warn_print = 1;
+       }
+
        memset(ld, 0, sizeof(*ld));
 
        err = io_queue_init(td->o.iodepth, &ld->aio_ctx);