netdev - Re: [PATCH] net_sched: accurate bytes/packets stats/rates

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Date:	Mon, 17 Jan 2011 10:16:35 +0100
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	Jarek Poplawski <jarkao2@...il.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Patrick McHardy <kaber@...sh.net>, jamal <hadi@...erus.ca>
Subject: Re: [PATCH] net_sched: accurate bytes/packets stats/rates

* Eric Dumazet | 2011-01-17 08:17:49 [+0100]:

>Hmm, considering qdisc stats are not used in kernel (only updated and
>reported to tc users) it seems to me counting arrival instead of
>departure rates is mostly useless for the user, if drops are ignored.
>
>(I am not speaking of direct drops, when we try to enqueue() this skb,
>but later ones, when another skb is enqueued and we drop a previously
>enqueued skb)
>
>User really wants to see the effective departure rate, to check its
>qdisc parameters in respect with kernel ones (HZ=100/1000, HIGH res
>timers off/on, ...)
>
>Arrival rates are of litle use. However, it might be good to have a
>second "bstats" only for dropped packets/bytes, or extend bstats in a
>compatible way (maybe adding fields to the end of structure)

Sure, qdiscs like CHOKe, SFQ, pfifo_head are only analyzable with this kind of
additional information. E.g. pfifo_head currently provides no statistic that
the queue length is possible underestimated and tunning is required.

Hagen
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