On Tue, Dec 27, 2022 at 05:43:57PM +0100, Philippe Mathieu-Daudé wrote:
> On 27/12/22 08:20, Longpeng(Mike) wrote:
> > From: Longpeng <longpe...@huawei.com>
> >
> > This allows the vhost device to batch the setup of all its host notifiers.
> > This significantly reduces the device starting time, e.g. the time spend
> > on enabling notifiers reduce from 376ms to 9.1ms for a VM with 64 vCPUs
> > and 3 vhost-vDPA generic devices (vdpa_sim_blk, 64vq per device)
> >
> > Signed-off-by: Longpeng <longpe...@huawei.com>
> > ---
> > hw/virtio/vhost.c | 24 ++++++++++++++++++++++++
> > 1 file changed, 24 insertions(+)
> >
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index 5994559da8..064d4abe5c 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -1562,16 +1562,25 @@ int vhost_dev_enable_notifiers(struct vhost_dev
> > *hdev, VirtIODevice *vdev)
> > return r;
> > }
> > + /*
> > + * Batch all the host notifiers in a single transaction to avoid
> > + * quadratic time complexity in address_space_update_ioeventfds().
> > + */
> > + memory_region_transaction_begin();
> > +
> > for (i = 0; i < hdev->nvqs; ++i) {
> > r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index
> > + i,
> > true);
> > if (r < 0) {
> > error_report("vhost VQ %d notifier binding failed: %d", i,
> > -r);
> > + memory_region_transaction_commit();
> > vhost_dev_disable_notifiers(hdev, vdev);
>
> Could we 'break' here, ...
>
> > return r;
> > }
> > }
> > + memory_region_transaction_commit();
> > +
> > return 0;
>
> ... and return 'r' here?
won't this commit twice? seems ugly ...
> > }
>
> Otherwise LGTM.
