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Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues
From: |
Halil Pasic |
Subject: |
Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues |
Date: |
Mon, 9 Nov 2020 19:53:03 +0100 |
On Mon, 9 Nov 2020 17:06:16 +0100
Cornelia Huck <cohuck@redhat.com> wrote:
> > @@ -20,6 +21,11 @@ static void virtio_ccw_blk_realize(VirtioCcwDevice
> > *ccw_dev, Error **errp)
> > {
> > VirtIOBlkCcw *dev = VIRTIO_BLK_CCW(ccw_dev);
> > DeviceState *vdev = DEVICE(&dev->vdev);
> > + VirtIOBlkConf *conf = &dev->vdev.conf;
> > +
> > + if (conf->num_queues == VIRTIO_BLK_AUTO_NUM_QUEUES) {
> > + conf->num_queues = MIN(4, current_machine->smp.cpus);
> > + }
>
> I would like to have a comment explaining the numbers here, however.
>
> virtio-pci has a pretty good explanation (use 1:1 for vqs:vcpus if
> possible, apply some other capping). 4 seems to be a bit arbitrary
> without explanation, although I'm sure you did some measurements :)
Frankly, I don't have any measurements yet. For the secure case,
I think Mimu has assessed the impact of multiqueue, hence adding Mimu to
the cc list. @Mimu can you help us out.
Regarding the normal non-protected VMs I'm in a middle of producing some
measurement data. This was admittedly a bit rushed because of where we
are in the cycle. Sorry to disappoint you.
The number 4 was suggested by Christian, maybe Christian does have some
readily available measurement data for the normal VM case. @Christian:
can you help me out?
Regards,
Halil
- [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Halil Pasic, 2020/11/09
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Christian Borntraeger, 2020/11/09
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Cornelia Huck, 2020/11/09
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues,
Halil Pasic <=
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Michael Mueller, 2020/11/10
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Michael Mueller, 2020/11/11
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Cornelia Huck, 2020/11/11
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Michael Mueller, 2020/11/11
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Halil Pasic, 2020/11/12
- Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues, Halil Pasic, 2020/11/11