netdev - Re: [PATCH v2 net-next RFC] Generic XDP

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Message-ID: <1491927148.10587.58.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 11 Apr 2017 09:12:28 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andy Gospodarek <andy@...yhouse.net>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        xdp-newbies@...r.kernel.org
Subject: Re: [PATCH v2 net-next RFC] Generic XDP

On Tue, 2017-04-11 at 09:05 -0700, Eric Dumazet wrote:

> Some kind of copybreak maybe ?
> 
> perf record -a -g sleep 5
> perf report --stdio
> 
> Copybreak is generally not really useful, and can have downsides.
> 
> Much better to let upper stacks deciding this.
> 
> For example, there is no point doing copy break for TCP ACK packets that
> are going to be consumed immediately.
> 
> There is also no point doing copy break in case the packet will be
> dropped (say by ... XDP ;) )


Yes :

#define BNXT_RX_COPY_THRESH 256

For optimal results, you probably want to remove copybreak.