Re: [dpdk-dev] [PATCH 5/8] driver/virtio:enqueue vhost TX offload

["Liu, Jijiang" <jijiang.liu@intel.com>]

From: David Marchand [mailto:david.marchand@6wind.com]
Sent: Friday, October 30, 2015 8:15 PM
To: Liu, Jijiang
Cc: dev@dpdk.org; Thomas Monjalon
Subject: Re: [dpdk-dev] [PATCH 5/8] driver/virtio:enqueue vhost TX offload

On Fri, Oct 30, 2015 at 12:45 PM, Liu, Jijiang <jijiang.liu@intel.com<mailto:jijiang.liu@intel.com>> wrote:

If the driver correctly reports negotiated offload capabilities (see my previous comment on patch 3), there is no need for the test on VIRTIO_NET_F_CSUM, because application is not supposed to ask for offloads on driver that do not support them.


> If the driver correctly reports negotiated offload capabilities, then application in guest will set the ol_flags in mbuf based on these offload capabilities.
If the VIRTIO_NET_F_CSUM is not enabled, and there is no need to call virtqueue_enqueue_offload() to check ol_flags in mbuf to see if the TX checksum and TSO is set ,and it will  not effect on the performance of disabling TX checksum path as much as possible.
So I think there is need for the check.

You are supposed to only handle mbuf with offloads if VIRTIO_NET_F_CSUM was enabled in the first place through the capabilities.
So looking at ol_flags means that you implicitely check for VIRTIO_NET_F_CSUM.
This is just an optimisation, so do as you like.
Anyway, I just want to confirm, is this patchset for 2.2 ?
>Yes, I will send new version for this patch set ASAP

--
David Marchand