From 10239edf86f137ce4c39b62ea9575e8053c549a0 Mon Sep 17 00:00:00 2001 From: Terry Lam Date: Sun, 15 Dec 2013 00:30:21 -0800 Subject: net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc This patch implements the first size-based qdisc that attempts to differentiate between small flows and heavy-hitters. The goal is to catch the heavy-hitters and move them to a separate queue with less priority so that bulk traffic does not affect the latency of critical traffic. Currently "less priority" means less weight (2:1 in particular) in a Weighted Deficit Round Robin (WDRR) scheduler. In essence, this patch addresses the "delay-bloat" problem due to bloated buffers. In some systems, large queues may be necessary for obtaining CPU efficiency, or due to the presence of unresponsive traffic like UDP, or just a large number of connections with each having a small amount of outstanding traffic. In these circumstances, HHF aims to reduce the HoL blocking for latency sensitive traffic, while not impacting the queues built up by bulk traffic. HHF can also be used in conjunction with other AQM mechanisms such as CoDel. To capture heavy-hitters, we implement the "multi-stage filter" design in the following paper: C. Estan and G. Varghese, "New Directions in Traffic Measurement and Accounting", in ACM SIGCOMM, 2002. Some configurable qdisc settings through 'tc': - hhf_reset_timeout: period to reset counter values in the multi-stage filter (default 40ms) - hhf_admit_bytes: threshold to classify heavy-hitters (default 128KB) - hhf_evict_timeout: threshold to evict idle heavy-hitters (default 1s) - hhf_non_hh_weight: Weighted Deficit Round Robin (WDRR) weight for non-heavy-hitters (default 2) - hh_flows_limit: max number of heavy-hitter flow entries (default 2048) Note that the ratio between hhf_admit_bytes and hhf_reset_timeout reflects the bandwidth of heavy-hitters that we attempt to capture (25Mbps with the above default settings). The false negative rate (heavy-hitter flows getting away unclassified) is zero by the design of the multi-stage filter algorithm. With 100 heavy-hitter flows, using four hashes and 4000 counters yields a false positive rate (non-heavy-hitters mistakenly classified as heavy-hitters) of less than 1e-4. Signed-off-by: Terry Lam Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/sched/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'net/sched/Makefile') diff --git a/net/sched/Makefile b/net/sched/Makefile index 35fa47a494ab..3442e5fbc4d7 100644 --- a/net/sched/Makefile +++ b/net/sched/Makefile @@ -40,6 +40,7 @@ obj-$(CONFIG_NET_SCH_QFQ) += sch_qfq.o obj-$(CONFIG_NET_SCH_CODEL) += sch_codel.o obj-$(CONFIG_NET_SCH_FQ_CODEL) += sch_fq_codel.o obj-$(CONFIG_NET_SCH_FQ) += sch_fq.o +obj-$(CONFIG_NET_SCH_HHF) += sch_hhf.o obj-$(CONFIG_NET_CLS_U32) += cls_u32.o obj-$(CONFIG_NET_CLS_ROUTE4) += cls_route.o -- cgit v1.2.3-59-g8ed1b