t/io_uring: add IORING_OP_NOP support
authorJens Axboe <axboe@kernel.dk>
Sun, 13 Jan 2019 05:14:54 +0000 (22:14 -0700)
committerJens Axboe <axboe@kernel.dk>
Sun, 13 Jan 2019 05:14:54 +0000 (22:14 -0700)
Doesn't do anything on the kernel side, just a round trip through
the SQ and CQ ring.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
os/io_uring.h
t/io_uring.c

index 74370ae..0f4460d 100644 (file)
@@ -47,6 +47,7 @@ struct io_uring_sqe {
 #define IORING_SETUP_SQPOLL    (1 << 1)        /* SQ poll thread */
 #define IORING_SETUP_SQ_AFF    (1 << 2)        /* sq_thread_cpu is valid */
 
+#define IORING_OP_NOP          0
 #define IORING_OP_READV                1
 #define IORING_OP_WRITEV       2
 #define IORING_OP_FSYNC                3
index d4160c3..8d3f3a9 100644 (file)
@@ -93,6 +93,7 @@ static int fixedbufs = 1;     /* use fixed user buffers */
 static int buffered = 0;       /* use buffered IO, not O_DIRECT */
 static int sq_thread_poll = 0; /* use kernel submission/poller thread */
 static int sq_thread_cpu = -1; /* pin above thread to this CPU */
+static int do_nop = 0;         /* no-op SQ ring commands */
 
 static int io_uring_register_buffers(struct submitter *s)
 {
@@ -101,6 +102,9 @@ static int io_uring_register_buffers(struct submitter *s)
                .nr_iovecs = DEPTH
        };
 
+       if (do_nop)
+               return 0;
+
        return syscall(__NR_sys_io_uring_register, s->ring_fd,
                        IORING_REGISTER_BUFFERS, &reg);
 }
@@ -110,6 +114,9 @@ static int io_uring_register_files(struct submitter *s)
        struct io_uring_register_files reg;
        int i;
 
+       if (do_nop)
+               return 0;
+
        s->fds = calloc(s->nr_files, sizeof(__s32));
        for (i = 0; i < s->nr_files; i++) {
                s->fds[i] = s->files[i].real_fd;
@@ -151,6 +158,11 @@ static void init_io(struct submitter *s, unsigned index)
        struct file *f;
        long r;
 
+       if (do_nop) {
+               sqe->opcode = IORING_OP_NOP;
+               return;
+       }
+
        if (s->nr_files == 1) {
                f = &s->files[0];
        } else {
@@ -248,11 +260,13 @@ static int reap_events(struct submitter *s)
                if (head == *ring->tail)
                        break;
                cqe = &ring->cqes[head & cq_ring_mask];
-               f = (struct file *) cqe->user_data;
-               f->pending_ios--;
-               if (cqe->res != BS) {
-                       printf("io: unexpected ret=%d\n", cqe->res);
-                       return -1;
+               if (!do_nop) {
+                       f = (struct file *) cqe->user_data;
+                       f->pending_ios--;
+                       if (cqe->res != BS) {
+                               printf("io: unexpected ret=%d\n", cqe->res);
+                               return -1;
+                       }
                }
                if (cqe->flags & IOCQE_FLAG_CACHEHIT)
                        s->cachehit++;
@@ -454,7 +468,7 @@ int main(int argc, char *argv[])
        struct rlimit rlim;
        void *ret;
 
-       if (argc < 2) {
+       if (!do_nop && argc < 2) {
                printf("%s: filename\n", argv[0]);
                return 1;
        }
@@ -464,7 +478,7 @@ int main(int argc, char *argv[])
                flags |= O_DIRECT;
 
        i = 1;
-       while (i < argc) {
+       while (!do_nop && i < argc) {
                struct file *f = &s->files[s->nr_files];
 
                fd = open(argv[i], flags);