netdev - Re: [virtio-dev] Re: [PATCH net-next v2 0/5] virtio: support packed ring

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Date:   Thu, 11 Oct 2018 09:48:48 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        virtio-dev@...ts.oasis-open.org, wexu@...hat.com,
        jfreimann@...hat.com
Subject: Re: [virtio-dev] Re: [PATCH net-next v2 0/5] virtio: support packed
 ring

On Thu, Oct 11, 2018 at 08:12:21PM +0800, Tiwei Bie wrote:
> > > But if it's not too late, I second for a OUT_OF_ORDER feature.
> > > Starting from in order can have much simpler code in driver.
> > > 
> > > Thanks
> > 
> > It's tricky to change the flag polarity because of compatibility
> > with legacy interfaces. Why is this such a big deal?
> > 
> > Let's teach drivers about IN_ORDER, then if devices
> > are in order it will get enabled by default.
> 
> Yeah, make sense.
> 
> Besides, I have done some further profiling and debugging
> both in kernel driver and DPDK vhost. Previously I was mislead
> by a bug in vhost code. I will send a patch to fix that bug.
> With that bug fixed, the performance of packed ring in the
> test between kernel driver and DPDK vhost is better now.

OK, if we get a performance gain on the virtio side, we can finally
upstream it. If you see that please re-post ASAP so we can
put it in the next kernel release.

-- 
MST