From: Rusty Russell <rusty@rustcorp.com.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, pagupta@redhat.com,
Pawel Moll <pawel.moll@arm.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>
Subject: Re: [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support
Date: Fri, 13 Feb 2015 13:22:09 +1030 [thread overview]
Message-ID: <874mqqbk12.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20150210104019.GD9505@redhat.com>
"Michael S. Tsirkin" <mst@redhat.com> writes:
> On Tue, Feb 10, 2015 at 12:02:37PM +1030, Rusty Russell wrote:
>> Jason Wang <jasowang@redhat.com> writes:
>> > This patch enables the interrupt coalescing setting through ethtool.
>>
>> The problem is that there's nothing network specific about interrupt
>> coalescing. I can see other devices wanting exactly the same thing,
>> which means we'd deprecate this in the next virtio standard.
>>
>> I think the right answer is to extend like we did with
>> vring_used_event(), eg:
>>
>> 1) Add a new feature VIRTIO_F_RING_COALESCE.
>> 2) Add another a 32-bit field after vring_used_event(), eg:
>> #define vring_used_delay(vr) (*(u32 *)((vr)->avail->ring[(vr)->num + 2]))
>>
>> This loses the ability to coalesce by number of frames, but we can still
>> do number of sg entries, as we do now with used_event, and we could
>> change virtqueue_enable_cb_delayed() to take a precise number if we
>> wanted.
>
> But do we expect delay to be update dynamically?
> If not, why not stick it in config space?
Hmm, we could update it dynamically (and will, in the case of ethtool).
But it won't be common, so we could append a field to
virtio_pci_common_cfg for PCI.
I think MMIO and CCW would be easy to extend too, but CC'd to check.
>> My feeling is that this should be a v1.0-only feature though
>> (eg. feature bit 33).
>
> Yes, e.g. we can't extend config space for legacy virtio pci.
Thanks,
Rusty.
next prev parent reply other threads:[~2015-02-13 2:52 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-09 8:39 [PATCH RFC v5 net-next 0/6] enable tx interrupts for virtio-net Jason Wang
2015-02-09 8:39 ` [PATCH RFC v5 net-next 1/6] virtio_ring: fix virtqueue_enable_cb() when only 1 buffers were pending Jason Wang
2015-02-10 1:03 ` Rusty Russell
2015-02-10 6:26 ` Jason Wang
2015-02-10 10:18 ` Michael S. Tsirkin
2015-02-10 23:58 ` Rusty Russell
2015-02-11 5:41 ` Jason Wang
2015-02-09 8:39 ` [PATCH RFC v5 net-next 2/6] virtio_ring: try to disable event index callbacks in virtqueue_disable_cb() Jason Wang
2015-02-10 1:07 ` Rusty Russell
2015-02-10 10:24 ` Michael S. Tsirkin
2015-02-11 5:55 ` Jason Wang
2015-02-09 8:39 ` [PATCH RFC v5 net-next 3/6] virtio_net: enable tx interrupt Jason Wang
2015-02-09 8:39 ` [PATCH RFC v5 net-next 4/6] virtio-net: add basic interrupt coalescing support Jason Wang
2015-02-10 1:32 ` Rusty Russell
2015-02-10 6:51 ` Jason Wang
2015-02-10 10:25 ` Michael S. Tsirkin
2015-02-10 10:40 ` Michael S. Tsirkin
2015-02-13 2:52 ` Rusty Russell [this message]
2015-02-13 12:41 ` Pawel Moll
2015-02-16 3:07 ` Rusty Russell
2015-02-13 18:19 ` Cornelia Huck
2015-02-16 3:19 ` Rusty Russell
2015-02-09 8:39 ` [PATCH RFC v5 net-next 5/6] vhost: let vhost_signal() returns whether signalled Jason Wang
2015-02-09 8:39 ` [PATCH RFC v5 net-next 6/6] vhost_net: interrupt coalescing support Jason Wang
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