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Re: [PATCH v2 2/4] virtio-scsi: default num_queues to -smp N
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH v2 2/4] virtio-scsi: default num_queues to -smp N |
Date: |
Thu, 30 Jan 2020 01:29:16 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 29/01/20 16:44, Stefan Hajnoczi wrote:
> On Mon, Jan 27, 2020 at 02:10:31PM +0100, Cornelia Huck wrote:
>> On Fri, 24 Jan 2020 10:01:57 +0000
>> Stefan Hajnoczi <address@hidden> wrote:
>>> @@ -47,10 +48,15 @@ static void vhost_scsi_pci_realize(VirtIOPCIProxy
>>> *vpci_dev, Error **errp)
>>> {
>>> VHostSCSIPCI *dev = VHOST_SCSI_PCI(vpci_dev);
>>> DeviceState *vdev = DEVICE(&dev->vdev);
>>> - VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
>>> + VirtIOSCSIConf *conf = &dev->vdev.parent_obj.parent_obj.conf;
>>> +
>>> + /* 1:1 vq to vcpu mapping is ideal because it avoids IPIs */
>>> + if (conf->num_queues == VIRTIO_SCSI_AUTO_NUM_QUEUES) {
>>> + conf->num_queues = current_machine->smp.cpus;
>> This now maps the request vqs 1:1 to the vcpus. What about the fixed
>> vqs? If they don't really matter, amend the comment to explain that?
> The fixed vqs don't matter. They are typically not involved in the data
> path, only the control path where performance doesn't matter.
Should we put a limit on the number of vCPUs? For anything above ~128
the guest is probably not going to be disk or network bound.
Paolo
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[PATCH v2 3/4] virtio-blk: default num_queues to -smp N, Stefan Hajnoczi, 2020/01/24
[PATCH v2 4/4] vhost-user-blk: default num_queues to -smp N, Stefan Hajnoczi, 2020/01/24
Re: [PATCH v2 0/4] virtio-pci: enable blk and scsi multi-queue by default, Stefano Garzarella, 2020/01/27