From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
kvm@vger.kernel.org, rusty@rustcorp.com.au, jasowang@redhat.com,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 5/5] virtio-scsi: introduce multiqueue support
Date: Tue, 04 Sep 2012 16:55:56 +0200 [thread overview]
Message-ID: <5046167C.3070109@redhat.com> (raw)
In-Reply-To: <20120904144754.GO9805@redhat.com>
Il 04/09/2012 16:47, Michael S. Tsirkin ha scritto:
>> > static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
>> > - struct virtqueue *vq)
>> > + struct virtqueue *vq, bool affinity)
>> > {
>> > spin_lock_init(&virtscsi_vq->vq_lock);
>> > virtscsi_vq->vq = vq;
>> > + if (affinity)
>> > + virtqueue_set_affinity(vq, virtqueue_get_queue_index(vq) -
>> > + VIRTIO_SCSI_VQ_BASE);
>> > }
>> >
> This means in practice if you have less virtqueues than CPUs,
> things are not going to work well, will they?
Not particularly. It could be better or worse than single queue
depending on the workload.
> Any idea what to do?
Two possibilities:
1) Add a stride argument to virtqueue_set_affinity, and make it equal to
the number of queues.
2) Make multiqueue the default in QEMU, and make the default number of
queues equal to the number of VCPUs.
I was going for (2).
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 5/5] virtio-scsi: introduce multiqueue support
Date: Tue, 04 Sep 2012 16:55:56 +0200 [thread overview]
Message-ID: <5046167C.3070109@redhat.com> (raw)
In-Reply-To: <20120904144754.GO9805@redhat.com>
Il 04/09/2012 16:47, Michael S. Tsirkin ha scritto:
>> > static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
>> > - struct virtqueue *vq)
>> > + struct virtqueue *vq, bool affinity)
>> > {
>> > spin_lock_init(&virtscsi_vq->vq_lock);
>> > virtscsi_vq->vq = vq;
>> > + if (affinity)
>> > + virtqueue_set_affinity(vq, virtqueue_get_queue_index(vq) -
>> > + VIRTIO_SCSI_VQ_BASE);
>> > }
>> >
> This means in practice if you have less virtqueues than CPUs,
> things are not going to work well, will they?
Not particularly. It could be better or worse than single queue
depending on the workload.
> Any idea what to do?
Two possibilities:
1) Add a stride argument to virtqueue_set_affinity, and make it equal to
the number of queues.
2) Make multiqueue the default in QEMU, and make the default number of
queues equal to the number of VCPUs.
I was going for (2).
Paolo
next prev parent reply other threads:[~2012-09-04 14:56 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-28 11:54 [PATCH 0/5] Multiqueue virtio-scsi Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 1/5] virtio-ring: move queue_index to vring_virtqueue Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-29 7:54 ` Jason Wang
2012-08-29 7:54 ` Jason Wang
2012-09-05 23:32 ` Rusty Russell
2012-09-05 23:32 ` Rusty Russell
2012-08-28 11:54 ` [PATCH 2/5] virtio: introduce an API to set affinity for a virtqueue Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-09-05 23:32 ` Rusty Russell
2012-09-05 23:32 ` Rusty Russell
2012-08-28 11:54 ` [PATCH 3/5] virtio-scsi: allocate target pointers in a separate memory block Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 14:07 ` Sasha Levin
2012-08-28 14:07 ` Sasha Levin
2012-08-28 14:25 ` Paolo Bonzini
2012-08-28 14:25 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 4/5] virtio-scsi: pass struct virtio_scsi to virtqueue completion function Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-08-28 11:54 ` [PATCH 5/5] virtio-scsi: introduce multiqueue support Paolo Bonzini
2012-08-28 11:54 ` Paolo Bonzini
2012-09-04 2:21 ` Nicholas A. Bellinger
2012-09-04 2:21 ` Nicholas A. Bellinger
2012-09-04 6:46 ` Paolo Bonzini
2012-09-04 6:46 ` Paolo Bonzini
2012-09-04 8:46 ` Michael S. Tsirkin
2012-09-04 8:46 ` Michael S. Tsirkin
2012-09-04 10:25 ` Paolo Bonzini
2012-09-04 10:25 ` Paolo Bonzini
2012-09-04 11:09 ` Michael S. Tsirkin
2012-09-04 11:09 ` Michael S. Tsirkin
2012-09-04 11:18 ` Paolo Bonzini
2012-09-04 11:18 ` Paolo Bonzini
2012-09-04 13:35 ` Michael S. Tsirkin
2012-09-04 13:35 ` Michael S. Tsirkin
2012-09-04 13:45 ` Paolo Bonzini
2012-09-04 13:45 ` Paolo Bonzini
2012-09-04 14:19 ` Michael S. Tsirkin
2012-09-04 14:19 ` Michael S. Tsirkin
2012-09-04 14:25 ` Paolo Bonzini
2012-09-04 14:25 ` Paolo Bonzini
2012-09-04 20:11 ` Nicholas A. Bellinger
2012-09-04 20:11 ` Nicholas A. Bellinger
2012-09-05 7:03 ` Paolo Bonzini
2012-09-05 7:03 ` Paolo Bonzini
2012-09-04 12:48 ` Michael S. Tsirkin
2012-09-04 12:48 ` Michael S. Tsirkin
2012-09-04 13:49 ` Paolo Bonzini
2012-09-04 13:49 ` Paolo Bonzini
2012-09-04 14:21 ` Michael S. Tsirkin
2012-09-04 14:21 ` Michael S. Tsirkin
2012-09-04 14:30 ` Paolo Bonzini
2012-09-04 14:30 ` Paolo Bonzini
2012-09-04 14:41 ` Michael S. Tsirkin
2012-09-04 14:41 ` Michael S. Tsirkin
2012-09-04 14:47 ` Michael S. Tsirkin
2012-09-04 14:47 ` Michael S. Tsirkin
2012-09-04 14:55 ` Paolo Bonzini [this message]
2012-09-04 14:55 ` Paolo Bonzini
2012-09-04 15:03 ` Michael S. Tsirkin
2012-09-04 15:03 ` Michael S. Tsirkin
2012-08-30 7:13 ` [PATCH 0/5] Multiqueue virtio-scsi Stefan Hajnoczi
2012-08-30 7:13 ` Stefan Hajnoczi
2012-08-30 14:53 ` Michael S. Tsirkin
2012-08-30 14:53 ` Michael S. Tsirkin
2012-08-30 15:45 ` Paolo Bonzini
2012-08-30 15:45 ` Paolo Bonzini
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