netdev - Re: [PATCH 0/2] net/sched: Add hardware specific counters to TC actions

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Date:   Thu, 9 Aug 2018 20:26:08 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Eelco Chaudron <echaudro@...hat.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, jiri@...nulli.us,
        Simon Horman <simon.horman@...ronome.com>
Subject: Re: [PATCH 0/2] net/sched: Add hardware specific counters to TC
 actions

On Thu,  9 Aug 2018 11:01:18 -0400, Eelco Chaudron wrote:
> Add hardware specific counters to TC actions which will be exported
> through the netlink API. This makes troubleshooting TC flower offload
> easier, as it possible to differentiate the packets being offloaded.

It is not immediately clear why this is needed.  The memory and
updating two sets of counters won't come for free, so perhaps a
stronger justification than troubleshooting is due? :S

Netdev has counters for fallback vs forwarded traffic, so you'd know
that traffic hits the SW datapath, plus the rules which are in_hw will
most likely not match as of today for flower (assuming correctness).

I'm slightly concerned about potential performance impact, would you
be able to share some numbers for non-trivial number of flows (100k
active?)?