netdev - Re: [PATCH v2 net-next 3/4] net: make listified RX functions return number of good packets

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Date:   Fri, 7 Sep 2018 11:44:30 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Eric Dumazet <eric.dumazet@...il.com>, <davem@...emloft.net>
CC:     <linux-net-drivers@...arflare.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net-next 3/4] net: make listified RX functions return
 number of good packets

On 07/09/18 03:27, Eric Dumazet wrote:
> On 09/06/2018 07:26 AM, Edward Cree wrote:
>> Signed-off-by: Edward Cree <ecree@...arflare.com>
> Lack of changelog here ?
>
> I do not know what is a good packet.
The comment on netif_receive_skb_list() defines this as "skbs for which
 netif_receive_skb() would have returned %NET_RX_SUCCESS".  But I shall put
 that into the changelog as well.

> You are adding a lot of conditional expressions, that cpu
> will mispredict quite often.
I don't see an alternative, since this is needed by patch #4 and I daresay
 there are other drivers that will also want to get NET_RX_SUCCESS-like
 information (possibly from regular receives as well as GRO; I'm not quite
 sure why sfc only cares about the latter).

> Typical micro benchmarks wont really notice.

Any suggestions on how to construct a test that will?