From: Hagen Paul Pfeifer <hagen@jauu.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: <netdev@vger.kernel.org>, Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior
Date: Thu, 01 Dec 2011 09:25:20 +0100 [thread overview]
Message-ID: <cfd2e2c26063da002d8afe76991ff0c1@localhost> (raw)
In-Reply-To: <1322710225.2577.1.camel@edumazet-laptop>
On Thu, 01 Dec 2011 04:30:25 +0100, Eric Dumazet wrote:
> Thats a multiply instead of a divide. On many cpus thats a lot faster.
>
> Think about a super packet (TSO) of 65000 bytes and cell_size=64
I've never imagined that I am going to say the following: you are wrong,
Eric! (ok, maybe you are right ;-)
TSO and Netem is a no-go. With netem you are strongly advised to disable
offloading. I mean TSO will result in _one_ delay of several minutes,
followed by a burst of packets. Instead of packets spaced by several
seconds (with the rate of 1000byte/s) - which is what you wan't.
To sum up: skb->len is _never_ larger as the MTU for (normal, correct)
network emulation setups with netem. This was the assumption why I
preferred the iterative solution over the div/mod solution.
Did I miss something?
Hagen
next prev parent reply other threads:[~2011-12-01 8:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-30 22:20 [PATCH v3 net-next 1/2] netem: rate extension Hagen Paul Pfeifer
2011-11-30 22:20 ` [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior Hagen Paul Pfeifer
2011-12-01 3:30 ` Eric Dumazet
2011-12-01 8:25 ` Hagen Paul Pfeifer [this message]
2011-12-01 9:01 ` Eric Dumazet
2011-12-01 9:32 ` [PATCH net-next] netem: fix build error on 32bit arches Eric Dumazet
2011-12-01 9:46 ` Hagen Paul Pfeifer
2011-12-01 11:04 ` David Laight
2011-12-01 11:19 ` Eric Dumazet
2011-12-01 17:46 ` David Miller
2011-12-01 9:36 ` [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior Hagen Paul Pfeifer
2011-12-01 16:24 ` Stephen Hemminger
2011-12-01 16:38 ` David Laight
2011-12-01 16:57 ` Stephen Hemminger
2011-12-01 18:25 ` Rick Jones
2011-12-01 4:19 ` [PATCH v3 net-next 1/2] netem: rate extension David Miller
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