netdev - Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

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Date:   Wed, 9 Dec 2020 08:44:33 -0700
From:   David Ahern <dsahern@...il.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        alardam@...il.com, magnus.karlsson@...el.com,
        bjorn.topel@...el.com, andrii.nakryiko@...il.com, kuba@...nel.org,
        ast@...nel.org, netdev@...r.kernel.org, davem@...emloft.net,
        hawk@...nel.org, jonathan.lemon@...il.com, bpf@...r.kernel.org,
        jeffrey.t.kirsher@...el.com, maciejromanfijalkowski@...il.com,
        intel-wired-lan@...ts.osuosl.org,
        Marek Majtyka <marekx.majtyka@...el.com>
Subject: Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

On 12/9/20 4:52 AM, Jesper Dangaard Brouer wrote:
> But I have redesigned the ndo_xdp_xmit call to take a bulk of packets
> (up-to 16) so it should not be a problem to solve this by sharing
> TX-queue and talking a lock per 16 packets.  I still recommend that,
> for fallback case,  you allocated a number a TX-queue and distribute
> this across CPUs to avoid hitting a congested lock (above measurements
> are the optimal non-congested atomic lock operation)

I have been meaning to ask you why 16 for the XDP batching? If the
netdev budget is 64, why not something higher like 32 or 64?