netdev - Re: [PATCH bpf-next] samples/bpf: optimize l2fwd performance in xdpsock

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Date:   Mon, 31 Aug 2020 23:02:33 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Magnus Karlsson <magnus.karlsson@...el.com>, bjorn.topel@...el.com,
        ast@...nel.org, netdev@...r.kernel.org, jonathan.lemon@...il.com
Cc:     bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] samples/bpf: optimize l2fwd performance in
 xdpsock

On 8/28/20 2:51 PM, Magnus Karlsson wrote:
> Optimize the throughput performance of the l2fwd sub-app in the
> xdpsock sample application by removing a duplicate syscall and
> increasing the size of the fill ring.
> 
> The latter needs some further explanation. We recommend that you set
> the fill ring size >= HW RX ring size + AF_XDP RX ring size. Make sure
> you fill up the fill ring with buffers at regular intervals, and you
> will with this setting avoid allocation failures in the driver. These
> are usually quite expensive since drivers have not been written to
> assume that allocation failures are common. For regular sockets,
> kernel allocated memory is used that only runs out in OOM situations
> that should be rare.
> 
> These two performance optimizations together lead to a 6% percent
> improvement for the l2fwd app on my machine.
> 
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>

Applied, thanks!