netdev - Re: Questions on XDP

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Date:   Wed, 22 Feb 2017 22:59:24 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Netdev <netdev@...r.kernel.org>,
        Tom Herbert <tom@...bertland.com>,
        Alexei Starovoitov <ast@...nel.org>,
        John Fastabend <john.r.fastabend@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>, brouer@...hat.com
Subject: Re: Questions on XDP

On Wed, 22 Feb 2017 09:08:53 -0800
John Fastabend <john.fastabend@...il.com> wrote:

> > GSO/TSO is getting into advanced stuff I would rather not have to get
> > into right now.  I figure we need to take this portion one step at a
> > time.  To support GSO we need more information like the mss.
> >   
> 
> Agreed lets get the driver support for basic things first. But this
> is on my list. I'm just repeating myself but VM to VM performance uses
> TSO/LRO heavily.

Sorry, but I get annoyed every time I hear we need to support
TSO/LRO/GRO for performance reasons.  If you take one step back, you
are actually saying we need bulking for better performance.  And the
bulking you are proposing is a TCP protocol specific bulking mechanism.

I'm saying is let's make bulking protocol agnostic, by doing it at the
packet level.  And once the bulk enters the VM, by-all-means it should
construct a GRO packet it can send into it's own network stack.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer