On Wed, May 28, 2025 at 03:09:07PM -0400, Stefan Hajnoczi wrote:
> Commit 816a430c517e ("util/aio: Defer disabling poll mode as long as
> possible") kept polling enabled when the event loop timeout is 0. Since
> there is no timeout the event loop will continue immediately and the
> overhead of disabling and re-enabling polling can be avoided.
>
> fdmon-io_uring.c is unable to take advantage of this optimization
> because its ->need_wait() function returns true whenever there are new
> io_uring SQEs to submit:
>
> if (timeout || ctx->fdmon_ops->need_wait(ctx)) {
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> Polling will be disabled even when timeout == 0.
>
> Extend the optimization to handle the case when need_wait() returns true
> and timeout == 0.
>
> Cc: Chao Gao <chao....@intel.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization: qemu.org | libguestfs.org
