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Re: [aqm] Gathering Queue Length Statistics

Toke Høiland-Jørgensen <toke@toke.dk> Thu, 26 February 2015 10:36 UTC

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From: Toke Høiland-Jørgensen <toke@toke.dk>
To: Mikael Abrahamsson <swmike@swm.pp.se>
References: <BAY176-W35105790F5BC047AA12309A5170@phx.gbl> <CAA93jw5dPhLmamcSHxD92b50XxmkkZNy28SWMkOSRFzBY3keBA@mail.gmail.com> <alpine.DEB.2.02.1502261125510.4007@uplift.swm.pp.se>
Date: Thu, 26 Feb 2015 11:36:03 +0100
In-Reply-To: <alpine.DEB.2.02.1502261125510.4007@uplift.swm.pp.se> (Mikael Abrahamsson's message of "Thu, 26 Feb 2015 11:30:00 +0100 (CET)")
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Cc: Dave Taht <dave.taht@gmail.com>, "aqm@ietf.org" <aqm@ietf.org>
Subject: Re: [aqm] Gathering Queue Length Statistics
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Mikael Abrahamsson <swmike@swm.pp.se> writes:

> I don't know how the Linux AQM system works, but exposing some of
> these counters through the proc subsystem (or something else), might
> work, and then a userspace daemon could poll this data as often as it
> wanted, then you don't even need the kernel to do averaging and
> keeping the data.

It's exposed via the Netlink interface, which is what `tc -s` shows:

qdisc fq_codel 110: dev enp2s0 parent 1:10 limit 1000p flows 1014 quantum 500 target 5.0ms interval 100.0ms ecn 
 Sent 16981968691 bytes 17816348 pkt (dropped 8, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0 
  maxpacket 13216 drop_overlimit 0 new_flow_count 6502039 ecn_mark 0
  new_flows_len 1 old_flows_len 5

The 'backlog 0b 0p' shows that the queue is currently empty, while the
lines below show qdisc-specific stats. But as Dave said, getting the
statistics has some locking issues that may (or will, probably) cause
trouble if trying to poll it too frequently...

-Toke

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