On Tue, 11/11 09:17, Ming Lei wrote:
> It isn't necessery to notify guest each time when one request
> is completed, and it should be enough to just notify one time
> for each running of virtio_scsi_iothread_handle_cmd().
>
> This patch supresses about 30K/sec write on eventfd.
>
> Signed-off-by: Ming Lei <ming....@canonical.com>
> ---
> hw/scsi/virtio-scsi-dataplane.c | 4 +++-
> hw/scsi/virtio-scsi.c | 26 +++++++++++++++++++++++++-
> include/hw/virtio/virtio-scsi.h | 4 ++++
> 3 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
> index df17229..294515a 100644
> --- a/hw/scsi/virtio-scsi-dataplane.c
> +++ b/hw/scsi/virtio-scsi-dataplane.c
> @@ -62,6 +62,7 @@ static VirtIOSCSIVring *virtio_scsi_vring_init(VirtIOSCSI
> *s,
> aio_set_event_notifier(s->ctx, &r->host_notifier, handler);
>
> r->parent = s;
> + r->qid = n;
>
> if (!vring_setup(&r->vring, VIRTIO_DEVICE(s), n)) {
> fprintf(stderr, "virtio-scsi: VRing setup failed\n");
> @@ -95,7 +96,8 @@ void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
> {
> vring_push(&req->vring->vring, &req->elem,
> req->qsgl.size + req->resp_iov.size);
> - event_notifier_set(&req->vring->guest_notifier);
> + req->dev->pending_guest_notify |= 1 << (req->vring->qid - 2);
> + qemu_bh_schedule(req->dev->guest_notify_bh);
> }
>
> static void virtio_scsi_iothread_handle_ctrl(EventNotifier *notifier)
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 6e34a2c..98411ef 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -86,6 +86,21 @@ static void virtio_scsi_complete_req(VirtIOSCSIReq *req)
> virtio_scsi_free_req(req);
> }
>
> +static void notify_guest_bh(void *opaque)
> +{
> + VirtIOSCSI *s = opaque;
> + unsigned int qid;
> + uint64_t pending = s->pending_guest_notify;
> +
> + s->pending_guest_notify = 0;
> +
> + while ((qid = ffsl(pending))) {
> + qid--;
> + event_notifier_set(&s->cmd_vrings[qid]->guest_notifier);
Don't we need to handle ctrlq and eventq as well?
> + pending &= ~(1 << qid);
> + }
> +}
> +
> static void virtio_scsi_bad_req(void)
> {
> error_report("wrong size for virtio-scsi headers");
> @@ -824,7 +839,12 @@ void virtio_scsi_common_realize(DeviceState *dev, Error
> **errp,
> }
>
> if (s->conf.iothread) {
> - virtio_scsi_set_iothread(VIRTIO_SCSI(s), s->conf.iothread);
> + VirtIOSCSI *vis = VIRTIO_SCSI(s);
> +
> + QEMU_BUILD_BUG_ON(VIRTIO_PCI_QUEUE_MAX > 64);
> + virtio_scsi_set_iothread(vis, s->conf.iothread);
> + vis->pending_guest_notify = 0;
> + vis->guest_notify_bh = aio_bh_new(vis->ctx, notify_guest_bh, vis);
> }
> }
>
> @@ -901,7 +921,11 @@ void virtio_scsi_common_unrealize(DeviceState *dev,
> Error **errp)
> {
> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(dev);
> + VirtIOSCSI *s = VIRTIO_SCSI(vs);
>
> + if (vs->conf.iothread) {
> + qemu_bh_delete(s->guest_notify_bh);
> + }
> g_free(vs->cmd_vqs);
> virtio_cleanup(vdev);
> }
> diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> index 9e1a49c..5e6c57e 100644
> --- a/include/hw/virtio/virtio-scsi.h
> +++ b/include/hw/virtio/virtio-scsi.h
> @@ -163,6 +163,7 @@ typedef struct {
> Vring vring;
> EventNotifier host_notifier;
> EventNotifier guest_notifier;
> + uint32_t qid;
Could this "bool notify_pending"? In this case pending_guest_notify in
VirtIOSCSI is not necessary. I guess looking into no more than 64
VirtIOSCSIVring elements in guest_notify_bh is not _that_ expensive so it's not
worth the complexity.
> } VirtIOSCSIVring;
>
> typedef struct VirtIOSCSICommon {
> @@ -198,6 +199,9 @@ typedef struct VirtIOSCSI {
> bool dataplane_fenced;
> Error *blocker;
> Notifier migration_state_notifier;
> +
> + QEMUBH *guest_notify_bh;
> + uint64_t pending_guest_notify;
Fam
> } VirtIOSCSI;
>
> typedef struct VirtIOSCSIReq {
> --
> 1.7.9.5
>
