netdev - Re: [PATCH v2 bpf-next] cpumap: bulk skb using netif_receive_skb

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Date:   Thu, 15 Apr 2021 18:03:55 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, brouer@...hat.com, song@...nel.org
Subject: Re: [PATCH v2 bpf-next] cpumap: bulk skb using netif_receive_skb_list

> On 4/15/21 8:05 AM, Daniel Borkmann wrote:

[...]
> >> &stats);
> > 
> > Given we stop counting drops with the netif_receive_skb_list(), we
> > should then
> > also remove drops from trace_xdp_cpumap_kthread(), imho, as otherwise it
> > is rather
> > misleading (as in: drops actually happening, but 0 are shown from the
> > tracepoint).
> > Given they are not considered stable API, I would just remove those to
> > make it clear
> > to users that they cannot rely on this counter anymore anyway.
> > 
> 
> What's the visibility into drops then? Seems like it would be fairly
> easy to have netif_receive_skb_list return number of drops.
> 

In order to return drops from netif_receive_skb_list() I guess we need to introduce
some extra checks in the hot path. Moreover packet drops are already accounted
in the networking stack and this is currently the only consumer for this info.
Does it worth to do so?

Regards,
Lorenzo

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