t/io_uring: Vectored fixed buffer test support for nvme passthrough path

The current kernel NVMe passthrough path already supports vectored IO
when using fixed buffers, but fio has not yet adapted it. This patch
aims to add a corresponding test interface in fio.

Test results:

taskset -c 1 t/io_uring -b512 -d64 -c2 -s2 -p1 -F1 -B1 -O0 -n1 -V1 -u1 -r4 /dev/ng1n1
submitter=0, tid=6179, file=/dev/ng1n1, nfiles=1, node=-1
polled=1, fixedbufs=1, register_files=1, buffered=1, QD=64
Engine=io_uring, sq_ring=64, cq_ring=64
IOPS=289.78K, BW=141MiB/s, IOS/call=1/1
IOPS=294.68K, BW=143MiB/s, IOS/call=1/1
IOPS=295.26K, BW=144MiB/s, IOS/call=1/1
Exiting on timeout
Maximum IOPS=295.26K

taskset -c 1 t/io_uring -b512 -d64 -c2 -s2 -p1 -F1 -B1 -O0 -n1 -V0 -u1 -r4 /dev/ng1n1
submitter=0, tid=6183, file=/dev/ng1n1, nfiles=1, node=-1
polled=1, fixedbufs=1, register_files=1, buffered=1, QD=64
Engine=io_uring, sq_ring=64, cq_ring=64
IOPS=292.31K, BW=142MiB/s, IOS/call=1/1
IOPS=295.79K, BW=144MiB/s, IOS/call=1/1
IOPS=290.78K, BW=141MiB/s, IOS/call=1/1
Exiting on timeout
Maximum IOPS=295.79K

Signed-off-by: Xiaobing Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: lreeze123

t/io_uring.c

@@ -146,14 +146,13 @@ static int random_io = 1;	/* random or sequential IO */
 static int register_ring = 1;	/* register ring */
 static int use_sync = 0;	/* use preadv2 */
 static int numa_placement = 0;	/* set to node of device */
+static int vectored = 0;	/* use vectored IO */
 static int pt = 0;		/* passthrough I/O or not */
 
 static unsigned long tsc_rate;
 
 #define TSC_RATE_FILE	"tsc-rate"
 
-static int vectored = 1;
-
 static float plist[] = { 1.0, 5.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0,
 			80.0, 90.0, 95.0, 99.0, 99.5, 99.9, 99.95, 99.99 };
 static int plist_len = 17;
@@ -461,28 +460,6 @@ static int io_uring_setup(unsigned entries, struct io_uring_params *p)
 	return ret;
 }
 
-static void io_uring_probe(int fd)
-{
-	struct io_uring_probe *p;
-	int ret;
-
-	p = calloc(1, sizeof(*p) + 256 * sizeof(struct io_uring_probe_op));
-	if (!p)
-		return;
-
-	ret = syscall(__NR_io_uring_register, fd, IORING_REGISTER_PROBE, p, 256);
-	if (ret < 0)
-		goto out;
-
-	if (IORING_OP_READ > p->ops_len)
-		goto out;
-
-	if ((p->ops[IORING_OP_READ].flags & IO_URING_OP_SUPPORTED))
-		vectored = 0;
-out:
-	free(p);
-}
-
 static int io_uring_enter(struct submitter *s, unsigned int to_submit,
 			  unsigned int min_complete, unsigned int flags)
 {
@@ -630,6 +607,12 @@ static void init_io_pt(struct submitter *s, unsigned index)
 		sqe->uring_cmd_flags = IORING_URING_CMD_FIXED;
 		sqe->buf_index = 0;
 	}
+	if (vectored) {
+		sqe->cmd_op = NVME_URING_CMD_IO_VEC;
+		cmd->addr = (unsigned long) &s->iovecs[index];
+		cmd->data_len = 1;
+		sqe->buf_index = 0;
+	}
 	cmd->nsid = f->nsid;
 	cmd->opcode = 2;
 }
@@ -927,8 +910,6 @@ static int setup_ring(struct submitter *s)
 	}
 	s->ring_fd = s->enter_ring_fd = fd;
 
-	io_uring_probe(fd);
-
 	if (fixedbufs) {
 		struct rlimit rlim;
 
@@ -1521,11 +1502,12 @@ static void usage(char *argv, int status)
 		" -S <bool> : Use sync IO (preadv2), default %d\n"
 		" -X <bool> : Use registered ring %d\n"
 		" -P <bool> : Automatically place on device home node %d\n"
+		" -V <bool> : Vectored IO, default %d\n"
 		" -u <bool> : Use nvme-passthrough I/O, default %d\n",
 		argv, DEPTH, BATCH_SUBMIT, BATCH_COMPLETE, BS, polled,
 		fixedbufs, register_files, nthreads, !buffered, do_nop,
 		stats, runtime == 0 ? "unlimited" : runtime_str, random_io, aio,
-		use_sync, register_ring, numa_placement, pt);
+		use_sync, register_ring, numa_placement, vectored, pt);
 	exit(status);
 }
 
@@ -1584,7 +1566,7 @@ int main(int argc, char *argv[])
 	if (!do_nop && argc < 2)
 		usage(argv[0], 1);
 
-	while ((opt = getopt(argc, argv, "d:s:c:b:p:B:F:n:N:O:t:T:a:r:D:R:X:S:P:u:h?")) != -1) {
+	while ((opt = getopt(argc, argv, "d:s:c:b:p:B:F:n:N:O:t:T:a:r:D:R:X:S:P:V:u:h?")) != -1) {
 		switch (opt) {
 		case 'a':
 			aio = !!atoi(optarg);
@@ -1662,6 +1644,9 @@ int main(int argc, char *argv[])
 		case 'P':
 			numa_placement = !!atoi(optarg);
 			break;
+		case 'V':
+			vectored = !!atoi(optarg);
+			break;
 		case 'u':
 			pt = !!atoi(optarg);
 			break;