Re: [PATCH net-next] netem: slotting with non-uniform distribution

[David Miller <davem@davemloft.net>]

From: Yousuk Seung <ysseung@google.com>
Date: Wed, 27 Jun 2018 10:32:19 -0700

> Extend slotting with support for non-uniform distributions. This is
> similar to netem's non-uniform distribution delay feature.
> 
> Commit f043efeae2f1 ("netem: support delivering packets in delayed
> time slots") added the slotting feature to approximate the behaviors
> of media with packet aggregation but only supported a uniform
> distribution for delays between transmission attempts. Tests with TCP
> BBR with emulated wifi links with non-uniform distributions produced
> more useful results.
> 
> Syntax:
>    slot dist DISTRIBUTION DELAY JITTER [packets MAX_PACKETS] \
>       [bytes MAX_BYTES]
> 
> The syntax and use of the distribution table is the same as in the
> non-uniform distribution delay feature. A file DISTRIBUTION must be
> present in TC_LIB_DIR (e.g. /usr/lib/tc) containing numbers scaled by
> NETEM_DIST_SCALE. A random value x is selected from the table and it
> takes DELAY + ( x * JITTER ) as delay. Correlation between values is not
> supported.
> 
> Examples:
>   Normal distribution delay with mean = 800us and stdev = 100us.
>   > tc qdisc add dev eth0 root netem slot dist normal 800us 100us
> 
>   Optionally set the max slot size in bytes and/or packets.
>   > tc qdisc add dev eth0 root netem slot dist normal 800us 100us \
>     bytes 64k packets 42
> 
> Signed-off-by: Yousuk Seung <ysseung@google.com>
> Acked-by: Eric Dumazet <edumazet@google.com>
> Acked-by: Neal Cardwell <ncardwell@google.com>

Applied.