From: Michal Soltys <soltys@ziu.info>
To: Jarek Poplawski <jarkao2@gmail.com>
Cc: Linux Netdev List <netdev@vger.kernel.org>
Subject: pkt_sched: Fix qdisc len in qdisc_peek_dequeued() [61c9eaf9008] - question
Date: Sun, 16 Nov 2014 14:04:05 +0100 [thread overview]
Message-ID: <5468A0C5.9010409@ziu.info> (raw)
Hi,
I was wondering (probably missing some subtleties) about that particular
patch, namely:
61c9eaf90081cbe6dc4f389e0056bff76eca19ec
Why would that qlen++ change be necessary ? As far as peeked qdisc sees
things, the packet is already deqeued and gone - so not really part of
the queue anymore in this context (not ever requeued either). More
advanced qdiscs such as say fq_codel - if for example they decide to
drop head during further enqueue operation - obviously won't even
consider the peeked packet.
Increasing qlen from what I can see artificially shortens queue by 1.
For some classful schedulers (say like hfsc that instantly peeks next
packet length after dequeuing), child qdiscs will be almost all the time
formally operating at queue size decreased by 1.
next reply other threads:[~2014-11-16 13:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-16 13:04 Michal Soltys [this message]
2014-11-16 18:15 ` pkt_sched: Fix qdisc len in qdisc_peek_dequeued() [61c9eaf9008] - question Eric Dumazet
2014-11-16 21:09 ` Michal Soltys
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