Am 20.12.2023 um 14:47 hat Stefan Hajnoczi geschrieben:
> Add the iothread-vq-mapping parameter to assign virtqueues to IOThreads.
> Store the vq:AioContext mapping in the new struct
> VirtIOBlockDataPlane->vq_aio_context[] field and refactor the code to
> use the per-vq AioContext instead of the BlockDriverState's AioContext.
>
> Reimplement --device virtio-blk-pci,iothread= and non-IOThread mode by
> assigning all virtqueues to the IOThread and main loop's AioContext in
> vq_aio_context[], respectively.
>
> The comment in struct VirtIOBlockDataPlane about EventNotifiers is
> stale. Remove it.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> @@ -177,19 +238,13 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
>
> trace_virtio_blk_data_plane_start(s);
>
> - r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
> + r = blk_set_aio_context(s->conf->conf.blk, s->vq_aio_context[0],
> + &local_err);
> if (r < 0) {
> error_report_err(local_err);
> goto fail_aio_context;
> }
This doesn't really have to be an error any more, we'll just submit I/O
from any thread we want no matter what the home AioContext of the
BlockBackend is.
So the only effect the blk_set_aio_context() has is that other users of
the image try to submit their requests from the same iothread as the
first virtqueue in the hope that this performs a bit better (maybe less
lock contention or whatever the idea was?)
> - /* Kick right away to begin processing requests already in vring */
> - for (i = 0; i < nvqs; i++) {
> - VirtQueue *vq = virtio_get_queue(s->vdev, i);
> -
> - event_notifier_set(virtio_queue_get_host_notifier(vq));
> - }
> -
> /*
> * These fields must be visible to the IOThread when it processes the
> * virtqueue, otherwise it will think dataplane has not started yet.
> @@ -206,8 +261,12 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
> if (!blk_in_drain(s->conf->conf.blk)) {
> for (i = 0; i < nvqs; i++) {
> VirtQueue *vq = virtio_get_queue(s->vdev, i);
> + AioContext *ctx = s->vq_aio_context[i];
>
> - virtio_queue_aio_attach_host_notifier(vq, s->ctx);
> + /* Kick right away to begin processing requests already in vring
> */
> + event_notifier_set(virtio_queue_get_host_notifier(vq));
The old code did this also for blk_in_drain() == true. Why don't we need
it there any more? Should the 'if' move inside the loop just around
attaching the notifier?
> + virtio_queue_aio_attach_host_notifier(vq, ctx);
> }
> }
> return 0;
Kevin
