On Fri, Feb 28, 2025 at 5:40 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
>
> On 3/1/25 00:16, Caleb Sander Mateos wrote:
> > Call io_find_buf_node() to avoid duplicating it in io_nop().
>
> IORING_NOP_FIXED_BUFFER interface looks odd, instead of pretending
> to use a buffer, it basically pokes directly into internal infra,
> it's not something userspace should be able to do.
I assumed it was just for benchmarking the overhead of fixed buffer
lookup. Since a normal IORING_OP_NOP doesn't use any buffer, it makes
sense for IORING_NOP_FIXED_BUFFER not to do anything with the fixed
buffer either.
Added in this commit:
commit a85f31052bce52111b4e9d5a536003481d0421d0
Author: Jens Axboe <axboe@xxxxxxxxx>
Date: Sun Oct 27 08:59:10 2024
io_uring/nop: add support for testing registered files and buffers
Useful for testing performance/efficiency impact of registered files
and buffers, vs (particularly) non-registered files.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Best,
Caleb
>
> Jens, did use it anywhere? It's new, I'd rather kill it or align with
> how requests consume buffers, i.e. addr+len, and then do
> io_import_reg_buf() instead. That'd break the api though, but would
> anyone care?
>
>
> > Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
> > ---
> > io_uring/nop.c | 13 ++-----------
> > 1 file changed, 2 insertions(+), 11 deletions(-)
> >
> > diff --git a/io_uring/nop.c b/io_uring/nop.c
> > index ea539531cb5f..28f06285fdc2 100644
> > --- a/io_uring/nop.c
> > +++ b/io_uring/nop.c
> > @@ -59,21 +59,12 @@ int io_nop(struct io_kiocb *req, unsigned int issue_flags)
> > ret = -EBADF;
> > goto done;
> > }
> > }
> > if (nop->flags & IORING_NOP_FIXED_BUFFER) {
> > - struct io_ring_ctx *ctx = req->ctx;
> > - struct io_rsrc_node *node;
> > -
> > - ret = -EFAULT;
> > - io_ring_submit_lock(ctx, issue_flags);
> > - node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
> > - if (node) {
> > - io_req_assign_buf_node(req, node);
> > - ret = 0;
> > - }
> > - io_ring_submit_unlock(ctx, issue_flags);
> > + if (!io_find_buf_node(req, issue_flags))
> > + ret = -EFAULT;
> > }
> > done:
> > if (ret < 0)
> > req_set_fail(req);
> > io_req_set_res(req, nop->result, 0);
>
> --
> Pavel Begunkov
>
