io_uring: utilize the io batching infrastructure for more efficient polled IO

Wire up using an io_comp_batch for f_op->iopoll(). If the lower stack
supports it, we can handle high rates of polled IO more efficiently.

This raises the single core efficiency on my system from ~6.1M IOPS to
~6.6M IOPS running a random read workload at depth 128 on two gen2
Optane drives.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cd77a13..d4631a5 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2458,6 +2458,7 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
 {
        struct io_kiocb *req, *tmp;
        unsigned int poll_flags = BLK_POLL_NOSLEEP;
+       DEFINE_IO_COMP_BATCH(iob);
        LIST_HEAD(done);
 
        /*
@@ -2483,17 +2484,20 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
                if (!list_empty(&done))
                        break;
 
-               ret = kiocb->ki_filp->f_op->iopoll(kiocb, NULL, poll_flags);
+               ret = kiocb->ki_filp->f_op->iopoll(kiocb, &iob, poll_flags);
                if (unlikely(ret < 0))
                        return ret;
                else if (ret)
                        poll_flags |= BLK_POLL_ONESHOT;
 
                /* iopoll may have completed current req */
-               if (READ_ONCE(req->iopoll_completed))
+               if (!rq_list_empty(iob.req_list) ||
+                   READ_ONCE(req->iopoll_completed))
                        list_move_tail(&req->inflight_entry, &done);
        }
 
+       if (!rq_list_empty(iob.req_list))
+               iob.complete(&iob);
        if (!list_empty(&done))
                io_iopoll_complete(ctx, nr_events, &done);