netdev - Re: [PATCH net-next 0/5] virtio-net: Add SCTP checksum offload support

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Date:   Wed, 18 Apr 2018 17:06:46 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Vlad Yasevich <vyasevic@...hat.com>
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Vladislav Yasevich <vyasevich@...il.com>,
        netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, jasowang@...hat.com,
        nhorman@...driver.com
Subject: Re: [PATCH net-next 0/5] virtio-net: Add SCTP checksum offload
 support

On Tue, Apr 17, 2018 at 04:35:18PM -0400, Vlad Yasevich wrote:
> On 04/02/2018 10:47 AM, Marcelo Ricardo Leitner wrote:
> > On Mon, Apr 02, 2018 at 09:40:01AM -0400, Vladislav Yasevich wrote:
> >> Now that we have SCTP offload capabilities in the kernel, we can add
> >> them to virtio as well.  First step is SCTP checksum.
> > 
> > Thanks.
> > 
> >> As for GSO, the way sctp GSO is currently implemented buys us nothing
> >> in added support to virtio.  To add true GSO, would require a lot of
> >> re-work inside of SCTP and would require extensions to the virtio
> >> net header to carry extra sctp data.
> > 
> > Can you please elaborate more on this? Is this because SCTP GSO relies
> > on the gso skb format for knowing how to segment it instead of having
> > a list of sizes?
> > 
> 
> it's mainly because all the true segmentation, placing data into chunks,
> has already happened.  All that GSO does is allow for higher bundling
> rate between VMs. If that is all SCTP GSO ever going to do, that fine,
> but the goal is to do real GSO eventually and potentially reduce the
> amount of memory copying we are doing.
> If we do that, any current attempt at GSO in virtio would have to be
> depricated and we'd need GSO2 or something like that.

Batching helps virtualization *a lot* though.
Are there actual plans for GSO2? Is it just for SCTP?

> 
> This is why, after doing the GSO support, I decided not to include it.
> 
> -vlad
> >   Marcelo
> >