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Message-ID: <20171003010245.f3op4t56crbjc4ke@ast-mbp>
Date: Mon, 2 Oct 2017 18:02:46 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: netdev@...r.kernel.org, jakub.kicinski@...ronome.com,
"Michael S. Tsirkin" <mst@...hat.com>, pavel.odintsov@...il.com,
Jason Wang <jasowang@...hat.com>, mchan@...adcom.com,
John Fastabend <john.fastabend@...il.com>,
peter.waskiewicz.jr@...el.com,
Daniel Borkmann <borkmann@...earbox.net>,
Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [net-next V3 PATCH 3/5] bpf: cpumap xdp_buff to skb conversion
and allocation
On Mon, Oct 02, 2017 at 06:05:29PM +0200, Jesper Dangaard Brouer wrote:
> + while ((xdp_pkt = __ptr_ring_consume(rcpu->queue))) {
> + struct sk_buff *skb;
> + int ret;
> +
> + /* Allow busy polling again */
> + empty_cnt = 0;
> +
> + skb = cpu_map_build_skb(rcpu, xdp_pkt);
> + if (!skb) {
> + page_frag_free(xdp_pkt);
> + continue;
> + }
> +
> + /* Inject into network stack */
> + ret = netif_receive_skb(skb);
> + if (ret == NET_RX_DROP)
> + drops++;
I thought the whole thing is an alternative to RPS,
but netif_receive_skb_internal() will call into RPS logic.
So the user has to make sure it disabled or they will
conflict in some weird way?
Or you're calling netif_receive_skb() to be able to call
generic XDP on that cpu again ?
But that prog can do cpumap redirect again?
sort-of recursive redirect? Is it really useful?
May be call into __netif_receive_skb_core() directly?
not sure.
I'm asking all these questions to make sure we think through
these implications before it becomes an abi.
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