From 0a9fe5c375b57fab6d18ed0a6a7f935eefb09db3 Mon Sep 17 00:00:00 2001 From: Yousuk Seung Date: Wed, 27 Jun 2018 10:32:19 -0700 Subject: netem: slotting with non-uniform distribution 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 Acked-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- include/uapi/linux/pkt_sched.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 37b5096ae97b..bad3c03bcf43 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -539,6 +539,7 @@ enum { TCA_NETEM_LATENCY64, TCA_NETEM_JITTER64, TCA_NETEM_SLOT, + TCA_NETEM_SLOT_DIST, __TCA_NETEM_MAX, }; @@ -581,6 +582,8 @@ struct tc_netem_slot { __s64 max_delay; __s32 max_packets; __s32 max_bytes; + __s64 dist_delay; /* nsec */ + __s64 dist_jitter; /* nsec */ }; enum { -- cgit