Re: [dpdk-dev] [PATCH 4/4] net/virtio: improve offload check performance

[Tiwei Bie <tiwei.bie@intel.com>]

On Mon, Jun 04, 2018 at 04:29:56PM +0200, Maxime Coquelin wrote:
> On 06/04/2018 01:55 PM, Tiwei Bie wrote:
> > On Fri, Jun 01, 2018 at 02:47:58PM +0200, Maxime Coquelin wrote:
[...]
> > > @@ -253,13 +246,15 @@ virtqueue_enqueue_xmit(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
> > >   	struct virtio_net_hdr *hdr;
> > >   	int offload;
> > > -	offload = tx_offload_enabled(vq->hw);
> > >   	head_idx = vq->vq_desc_head_idx;
> > >   	idx = head_idx;
> > >   	dxp = &vq->vq_descx[idx];
> > >   	dxp->cookie = (void *)cookie;
> > >   	dxp->ndescs = needed;
> > > +	offload = vq->hw->has_tx_offload &&
> > > +		(cookie->ol_flags & PKT_TX_OFFLOAD_MASK);
> > 
> > If features aren't negotiated, I think there is no need to
> > check ol_flags and update the net header.
> 
> Isn't what the code is doing?
> has_tx_offload will be false if none of the Tx offload features have
> been negotiated, so ol_flags won't be checked in that case.

Hmm.. Somehow I treated 'and' as 'or'..

I have another question. When 'can_push' is false
and 'vq->hw->has_tx_offload' is true, there will
be a chance that virtio net hdr won't be zeroed
when ol_flags doesn't specify any Tx offloads.

Best regards,
Tiwei Bie