From: Tiwei Bie <tiwei.bie@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: zhihong.wang@intel.com, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 4/4] net/virtio: improve offload check performance
Date: Tue, 5 Jun 2018 20:21:28 +0800 [thread overview]
Message-ID: <20180605122128.GA28786@debian> (raw)
In-Reply-To: <b8e91f1c-1d9c-f07c-6aa6-4944b88ea93f@redhat.com>
On Tue, Jun 05, 2018 at 01:58:00PM +0200, Maxime Coquelin wrote:
> On 06/05/2018 01:20 PM, Tiwei Bie wrote:
> > On Tue, Jun 05, 2018 at 11:43:11AM +0200, Maxime Coquelin wrote:
> > > On 06/05/2018 05:10 AM, Tiwei Bie wrote:
> > > > 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.
> > >
> > > Right, good catch.
> > > It may be better to remove this small optimization.
> > > Indeed, with the series, if the application does not enable offloads,
> > > then the Virtio features are re-negotiated with the offload features.
> >
> > Yeah. It's a good idea to disable the features when
> > the corresponding Tx offloads aren't requested by
> > the applications! I like it!
> >
> > This issue happens for the mbufs whose ol_flags
> > doesn't specify Tx offloads when applications
> > enable Tx offloads and can_push is false. I think
> > when applications enable Tx offloads, although
> > most packets to be sent will have Tx offloads
> > specified in their ol_flags, it's still possible
> > that some packets don't have Tx offloads specified
> > in their ol_flags.
>
> Reading again my reply, I think it wasn't clear enough,
> let me rephrase it.
>
> My proposal is to keep disabling the features if the corresponding
> Tx offloads aren't negotiated by the application, but just to remove the
> check on mbuf's ol_flags, so:
> offload = vq->hw->has_tx_offload;
>
> Doing that, we retrieve the old behaviour, i.e. if Virtio features are
> negotiated but no ol_flags set, virtio-net header will be cleared.
It sounds good! Thanks!
Best regards,
Tiwei Bie
next prev parent reply other threads:[~2018-06-05 12:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-01 12:47 [dpdk-dev] [PATCH 0/4] net/virtio: Tx path selection and offload improvements Maxime Coquelin
2018-06-01 12:47 ` [dpdk-dev] [PATCH 1/4] net/virtio: use simple path for Tx even if Rx mergeable Maxime Coquelin
2018-06-01 12:47 ` [dpdk-dev] [PATCH 2/4] net/vhost: improve Tx path selection Maxime Coquelin
2018-06-04 12:25 ` Tiwei Bie
2018-06-01 12:47 ` [dpdk-dev] [PATCH 3/4] net/virtio: don't use simple Rx path if TCP LRO requested Maxime Coquelin
2018-06-04 11:59 ` Tiwei Bie
2018-06-04 14:32 ` Maxime Coquelin
2018-06-05 13:39 ` Maxime Coquelin
2018-06-01 12:47 ` [dpdk-dev] [PATCH 4/4] net/virtio: improve offload check performance Maxime Coquelin
2018-06-04 11:55 ` Tiwei Bie
2018-06-04 14:29 ` Maxime Coquelin
2018-06-05 3:10 ` Tiwei Bie
2018-06-05 9:43 ` Maxime Coquelin
2018-06-05 11:20 ` Tiwei Bie
2018-06-05 11:58 ` Maxime Coquelin
2018-06-05 12:21 ` Tiwei Bie [this message]
2018-06-04 7:42 ` [dpdk-dev] [PATCH 0/4] net/virtio: Tx path selection and offload improvements Maxime Coquelin
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