Adds support for fq's Earliest Departure Time to HBM (Host Bandwidth
Manager). Includes a new BPF program supporting EDT, and also updates
corresponding programs.
It will drop packets with an EDT of more than 500us in the future
unless the packet belongs to a flow with less than 2 packets in flight.
This is done so each flow has at least 2 packets in flight, so they
will not starve, and also to help prevent delayed ACK timeouts.
It will also work with ECN enabled traffic, where the packets will be
CE marked if their EDT is more than 50us in the future.
The table below shows some performance numbers. The flows are back to
back RPCS. One server sending to another, either 2 or 4 flows.
One flow is a 10KB RPC, the rest are 1MB RPCs. When there are more
than one flow of a given RPC size, the numbers represent averages.
The rate limit applies to all flows (they are in the same cgroup).
Tests ending with "-edt" ran with the new BPF program supporting EDT.
Tests ending with "-hbt" ran on top HBT qdisc with the specified rate
(i.e. no HBM). The other tests ran with the HBM BPF program included
in the HBM patch-set.
EDT has limited value when using DCTCP, but it helps in many cases when
using Cubic. It usually achieves larger link utilization and lower
99% latencies for the 1MB RPCs.
HBM ends up queueing a lot of packets with its default parameter values,
reducing the goodput of the 10KB RPCs and increasing their latency. Also,
the RTTs seen by the flows are quite large.
Aggr 10K 10K 10K 1MB 1MB 1MB
Limit rate drops RTT rate P90 P99 rate P90 P99
Test rate Flows Mbps % us Mbps us us Mbps ms ms
-------- ---- ----- ---- ----- --- ---- ---- ---- ---- ---- ----
cubic 1G 2 904 0.02 108 257 511 539 647 13.4 24.5
cubic-edt 1G 2 982 0.01 156 239 656 967 743 14.0 17.2
dctcp 1G 2 977 0.00 105 324 408 744 653 14.5 15.9
dctcp-edt 1G 2 981 0.01 142 321 417 811 660 15.7 17.0
cubic-htb 1G 2 919 0.00 1825 40 2822 4140 879 9.7 9.9
cubic 200M 2 155 0.30 220 81 532 655 74 283 450
cubic-edt 200M 2 188 0.02 222 87 1035 1095 101 84 85
dctcp 200M 2 188 0.03 111 77 912 939 111 76 325
dctcp-edt 200M 2 188 0.03 217 74 1416 1738 114 76 79
cubic-htb 200M 2 188 0.00 5015 8 14ms 15ms 180 48 50
cubic 1G 4 952 0.03 110 165 516 546 262 38 154
cubic-edt 1G 4 973 0.01 190 111 1034 1314 287 65 79
dctcp 1G 4 951 0.00 103 180 617 905 257 37 38
dctcp-edt 1G 4 967 0.00 163 151 732 1126 272 43 55
cubic-htb 1G 4 914 0.00 3249 13 7ms 8ms 300 29 34
cubic 5G 4 4236 0.00 134 305 490 624 1310 10 17
cubic-edt 5G 4 4865 0.00 156 306 425 759 1520 10 16
dctcp 5G 4 4936 0.00 128 485 221 409 1484 7 9
dctcp-edt 5G 4 4924 0.00 148 390 392 623 1508 11 26
v1 -> v2: Incorporated Andrii's suggestions
v2 -> v3: Incorporated Yonghong's suggestions
v3 -> v4: Removed credit update that is not needed
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Adds more stats to HBM, including average cwnd and rtt of all TCP
flows, percents of packets that are ecn ce marked and distribution
of return values.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The bpf_printk macro was moved to bpf_helpers.h which is included in all
example programs.
Signed-off-by: Michal Rostecki <mrostecki@opensuse.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
A cgroup skb BPF program to limit cgroup output bandwidth.
It uses a modified virtual token bucket queue to limit average
egress bandwidth. The implementation uses credits instead of tokens.
Negative credits imply that queueing would have happened (this is
a virtual queue, so no queueing is done by it. However, queueing may
occur at the actual qdisc (which is not used for rate limiting).
This implementation uses 3 thresholds, one to start marking packets and
the other two to drop packets:
CREDIT
- <--------------------------|------------------------> +
| | | 0
| Large pkt |
| drop thresh |
Small pkt drop Mark threshold
thresh
The effect of marking depends on the type of packet:
a) If the packet is ECN enabled, then the packet is ECN ce marked.
The current mark threshold is tuned for DCTCP.
c) Else, it is dropped if it is a large packet.
If the credit is below the drop threshold, the packet is dropped.
Note that dropping a packet through the BPF program does not trigger CWR
(Congestion Window Reduction) in TCP packets. A future patch will add
support for triggering CWR.
This BPF program actually uses 2 drop thresholds, one threshold
for larger packets (>= 120 bytes) and another for smaller packets. This
protects smaller packets such as SYNs, ACKs, etc.
The default bandwidth limit is set at 1Gbps but this can be changed by
a user program through a shared BPF map. In addition, by default this BPF
program does not limit connections using loopback. This behavior can be
overwritten by the user program. There is also an option to calculate
some statistics, such as percent of packets marked or dropped, which
the user program can access.
A latter patch provides such a program (hbm.c)
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
brakmo