netdev - Re: [PATCH net-next v2] net: sched: red: don't reset the backlog on every stat dump

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Message-ID: <20180117105043.GB2114@nanopsycho>
Date:   Wed, 17 Jan 2018 11:50:43 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     davem@...emloft.net, Nogah Frankel <nogahf@...lanox.com>,
        netdev@...r.kernel.org, oss-drivers@...ronome.com,
        xiyou.wangcong@...il.com, edumazet@...gle.com,
        Yuval Mintz <yuvalm@...lanox.com>
Subject: Re: [PATCH net-next v2] net: sched: red: don't reset the backlog on
 every stat dump

Mon, Jan 15, 2018 at 05:01:26AM CET, jakub.kicinski@...ronome.com wrote:
>Commit 0dfb33a0d7e2 ("sch_red: report backlog information") copied
>child's backlog into RED's backlog.  Back then RED did not maintain
>its own backlog counts.  This has changed after commit 2ccccf5fb43f
>("net_sched: update hierarchical backlog too") and commit d7f4f332f082
>("sch_red: update backlog as well").  Copying is no longer necessary.
>
>Tested:
>
>$ tc -s qdisc show dev veth0
>qdisc red 1: root refcnt 2 limit 400000b min 30000b max 30000b ecn
> Sent 20942 bytes 221 pkt (dropped 0, overlimits 0 requeues 0)
> backlog 1260b 14p requeues 14
>  marked 0 early 0 pdrop 0 other 0
>qdisc tbf 2: parent 1: rate 1Kbit burst 15000b lat 3585.0s
> Sent 20942 bytes 221 pkt (dropped 0, overlimits 138 requeues 0)
> backlog 1260b 14p requeues 14
>
>Recently RED offload was added.  We need to make sure drivers don't
>depend on resetting the stats.  This means backlog should be treated
>like any other statistic:
>
>  total_stat = new_hw_stat - prev_hw_stat;
>
>Adjust mlxsw.
>
>Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>