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Date: Thu, 01 Dec 2011 10:36:56 +0100 From: Hagen Paul Pfeifer <hagen@...u.net> To: Eric Dumazet <eric.dumazet@...il.com> Cc: <netdev@...r.kernel.org>, Stephen Hemminger <shemminger@...tta.com> Subject: Re: [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior 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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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