Re: [Qemu-devel] [PATCH v1] virtio-net: enable configurable tx queue size

[Eric Blake]

On 06/05/2017 10:38 AM, Michael S. Tsirkin wrote:
> On Mon, Jun 05, 2017 at 04:57:29PM +0800, Wei Wang wrote:
>> This patch enables the virtio-net tx queue size to be configurable
>> between 256 and 1024 by the user. The queue size specified by the
>> user should be power of 2. If "tx_queue_size" is not offered by the
>> user, the default queue size, 1024, will be used.
>>

>> +    if (n->net_conf.tx_queue_size < VIRTIO_NET_TX_QUEUE_MIN_SIZE ||
>> +        n->net_conf.tx_queue_size > VIRTQUEUE_MAX_SIZE ||
>> +        (n->net_conf.tx_queue_size & (n->net_conf.tx_queue_size - 1))) {
> 
> Pls use is_power_of_2.
> 
>> +        error_setg(errp, "Invalid tx_queue_size (= %" PRIu16 "), "
>> +                   "must be a power of 2 between %d and %d.",

No trailing '.' in error_setg() messages, please.

>> +                   n->net_conf.tx_queue_size, VIRTIO_NET_TX_QUEUE_MIN_SIZE,
>> +                   VIRTQUEUE_MAX_SIZE);
> 
> I think management will need a way to discover the limits for
> this value. Not sure how. Cc QAPI maintainers.

Is this something that can be documented? Or is it a runtime-variable
limit, where you will need to query the limit on a per-machine basis?
Given that it looks like compile-time documentation, I'm leaning towards
documentation being sufficient.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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