netdev - Re: [PATCH net-next] tcp: add optional per socket transmit delay

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Date:   Wed, 12 Jun 2019 11:03:44 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] tcp: add optional per socket transmit delay

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon, 10 Jun 2019 20:03:34 -0700

> Adding delays to TCP flows is crucial for studying behavior
> of TCP stacks, including congestion control modules.
> 
> Linux offers netem module, but it has unpractical constraints :
> - Need root access to change qdisc
> - Hard to setup on egress if combined with non trivial qdisc like FQ
> - Single delay for all flows.
> 
> EDT (Earliest Departure Time) adoption in TCP stack allows us
> to enable a per socket delay at a very small cost.
> 
> Networking tools can now establish thousands of flows, each of them
> with a different delay, simulating real world conditions.
> 
> This requires FQ packet scheduler or a EDT-enabled NIC.
> 
> This patchs adds TCP_TX_DELAY socket option, to set a delay in
> usec units.
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied to net-next and build testing.

Thanks.