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 10:36:56 +0100 [thread overview]
Message-ID: <61abe6ff1aa870d1b885ce88814920d4@localhost> (raw)
In-Reply-To: <1322730108.2335.3.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
On Thu, 01 Dec 2011 10:01:48 +0100, Eric Dumazet wrote:
> Yes :)
damn!
> I want to be able to use netem on a 10Gigabit link, and simulate a 5ms
> delay. I already will hit the shared qdisc bottleneck, dont force me to
> use small packets !
No I don't want that. But with 10Gb/s links you will have packet
scheduling problems anyway - if you focus on an _accurate_ delay. A static
delay differs from rate shaping in use case. In the later we (and probably
you) want a exact/realistic spacing between packets.
Due to timer and scheduling granularity somewhere in between 1bit/s and
10Gb/s netem rate (and tbf) will not scale anymore. You will see burst and
inaccurate spacings, far away from what you want to emulate. For us we want
a realistic and clean behavior, if the result of the emulation is not
identical to the emulated link/device we cannot use it (some background
information).
Anyway: I was not sure what solution you prefer - for us both are
identical. That's why I presented two solutions, so you can pick up the
favorite one. I will re-code the calculation using a reciprocal divide.
Thanks Eric!
Hagen
next prev parent reply other threads:[~2011-12-01 9:36 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
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 ` Hagen Paul Pfeifer [this message]
2011-12-01 16:24 ` [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior 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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