[dpdk-dev] [PATCH 4/5] vhost: do not use rte_memcpy for virtio_hdr copy

[Xie, Huawei]

On 1/27/2016 2:02 PM, Yuanhan Liu wrote:
> On Wed, Jan 27, 2016 at 05:56:56AM +0000, Xie, Huawei wrote:
>> On 1/27/2016 11:22 AM, Yuanhan Liu wrote:
>>> On Wed, Jan 27, 2016 at 02:46:39AM +0000, Xie, Huawei wrote:
>>>> On 12/3/2015 2:03 PM, Yuanhan Liu wrote:
>>>>> +	if (vq->vhost_hlen == sizeof(struct virtio_net_hdr_mrg_rxbuf)) {
>>>>> +		*(struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr = hdr;
>>>>> +	} else {
>>>>> +		*(struct virtio_net_hdr *)(uintptr_t)desc_addr = hdr.hdr;
>>>>> +	}
>>>> Thanks!
>>>> We might simplify this further. Just reset the first two fields flags
>>>> and gso_type.
>>> What's this "simplification" for? Don't even to say that we will add
>>> TSO support, which modifies few more files, such as csum_start: reseting
>>> the first two fields only is wrong here.
>> I know TSO before commenting, but at least in this implementation and
>> this specific patch, i guess zeroing two fields are enough.
>>
>> What is wrong resetting only two fields?
> I then have to ask "What is the benifit of resetting only two fields"?
> If doing so, we have to change it back for TSO. My proposal requires no
> extra change when adding TSO support.

? Benefit is we save four unnecessary stores.

>
> 	--yliu
>