bpf: Add support for fq's EDT to HBM
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>
This commit is contained in:
brakmo
Daniel Borkmann
parent
33bae185f7
commit
71634d7f92
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@ -168,6 +168,7 @@ always += task_fd_query_kern.o
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always += xdp_sample_pkts_kern.o
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always += ibumad_kern.o
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always += hbm_out_kern.o
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always += hbm_edt_kern.o
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KBUILD_HOSTCFLAGS += -I$(objtree)/usr/include
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KBUILD_HOSTCFLAGS += -I$(srctree)/tools/lib/bpf/
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@ -272,6 +273,7 @@ $(src)/*.c: verify_target_bpf $(LIBBPF)
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$(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h
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$(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
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$(obj)/hbm.o: $(src)/hbm.h
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$(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
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# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
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# But, there is no easy way to fix it, so just exclude it since it is
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@ -14,7 +14,7 @@ Usage() {
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echo "loads. The output is the goodput in Mbps (unless -D was used)."
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echo ""
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echo "USAGE: $name [out] [-b=<prog>|--bpf=<prog>] [-c=<cc>|--cc=<cc>]"
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echo " [-D] [-d=<delay>|--delay=<delay>] [--debug] [-E]"
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echo " [-D] [-d=<delay>|--delay=<delay>] [--debug] [-E] [--edt]"
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echo " [-f=<#flows>|--flows=<#flows>] [-h] [-i=<id>|--id=<id >]"
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echo " [-l] [-N] [--no_cn] [-p=<port>|--port=<port>] [-P]"
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echo " [-q=<qdisc>] [-R] [-s=<server>|--server=<server]"
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@ -30,6 +30,7 @@ Usage() {
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echo " other detailed information. This information is"
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echo " test dependent (i.e. iperf3 or netperf)."
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echo " -E enable ECN (not required for dctcp)"
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echo " --edt use fq's Earliest Departure Time (requires fq)"
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echo " -f or --flows number of concurrent flows (default=1)"
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echo " -i or --id cgroup id (an integer, default is 1)"
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echo " -N use netperf instead of iperf3"
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@ -130,13 +131,12 @@ processArgs () {
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details=1
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;;
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-E)
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ecn=1
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ecn=1
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;;
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--edt)
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flags="$flags --edt"
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qdisc="fq"
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;;
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# Support for upcomming fq Early Departure Time egress rate limiting
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#--edt)
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# prog="hbm_out_edt_kern.o"
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# qdisc="fq"
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# ;;
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-f=*|--flows=*)
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flows="${i#*=}"
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;;
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@ -228,8 +228,8 @@ if [ "$netem" -ne "0" ] ; then
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tc qdisc del dev lo root > /dev/null 2>&1
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tc qdisc add dev lo root netem delay $netem\ms > /dev/null 2>&1
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elif [ "$qdisc" != "" ] ; then
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tc qdisc del dev lo root > /dev/null 2>&1
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tc qdisc add dev lo root $qdisc > /dev/null 2>&1
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tc qdisc del dev eth0 root > /dev/null 2>&1
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tc qdisc add dev eth0 root $qdisc > /dev/null 2>&1
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fi
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n=0
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@ -399,7 +399,9 @@ fi
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if [ "$netem" -ne "0" ] ; then
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tc qdisc del dev lo root > /dev/null 2>&1
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fi
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if [ "$qdisc" != "" ] ; then
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tc qdisc del dev eth0 root > /dev/null 2>&1
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fi
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sleep 2
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hbmPid=`ps ax | grep "hbm " | grep --invert-match "grep" | awk '{ print $1 }'`
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@ -62,6 +62,7 @@ bool loopback_flag;
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bool debugFlag;
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bool work_conserving_flag;
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bool no_cn_flag;
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bool edt_flag;
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static void Usage(void);
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static void read_trace_pipe2(void);
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@ -372,9 +373,14 @@ static int run_bpf_prog(char *prog, int cg_id)
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fprintf(fout, "avg rtt:%d\n",
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(int)(qstats.sum_rtt / (qstats.pkts_total + 1)));
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// Average credit
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fprintf(fout, "avg credit:%d\n",
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(int)(qstats.sum_credit /
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(1500 * ((int)qstats.pkts_total) + 1)));
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if (edt_flag)
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fprintf(fout, "avg credit_ms:%.03f\n",
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(qstats.sum_credit /
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(qstats.pkts_total + 1.0)) / 1000000.0);
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else
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fprintf(fout, "avg credit:%d\n",
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(int)(qstats.sum_credit /
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(1500 * ((int)qstats.pkts_total ) + 1)));
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// Return values stats
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for (k = 0; k < RET_VAL_COUNT; k++) {
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@ -408,6 +414,7 @@ static void Usage(void)
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" Where:\n"
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" -o indicates egress direction (default)\n"
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" -d print BPF trace debug buffer\n"
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" --edt use fq's Earliest Departure Time\n"
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" -l also limit flows using loopback\n"
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" -n <#> to create cgroup \"/hbm#\" and attach prog\n"
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" Default is /hbm1\n"
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@ -433,6 +440,7 @@ int main(int argc, char **argv)
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char *optstring = "iodln:r:st:wh";
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struct option loptions[] = {
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{"no_cn", 0, NULL, 1},
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{"edt", 0, NULL, 2},
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{NULL, 0, NULL, 0}
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};
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@ -441,6 +449,10 @@ int main(int argc, char **argv)
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case 1:
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no_cn_flag = true;
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break;
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case 2:
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prog = "hbm_edt_kern.o";
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edt_flag = true;
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break;
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case'o':
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break;
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case 'd':
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@ -0,0 +1,168 @@
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// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2019 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* Sample Host Bandwidth Manager (HBM) BPF program.
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*
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* A cgroup skb BPF egress program to limit cgroup output bandwidth.
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* It uses a modified virtual token bucket queue to limit average
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* egress bandwidth. The implementation uses credits instead of tokens.
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* Negative credits imply that queueing would have happened (this is
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* a virtual queue, so no queueing is done by it. However, queueing may
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* occur at the actual qdisc (which is not used for rate limiting).
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*
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* This implementation uses 3 thresholds, one to start marking packets and
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* the other two to drop packets:
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* CREDIT
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* - <--------------------------|------------------------> +
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* | | | 0
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* | Large pkt |
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* | drop thresh |
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* Small pkt drop Mark threshold
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* thresh
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*
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* The effect of marking depends on the type of packet:
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* a) If the packet is ECN enabled and it is a TCP packet, then the packet
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* is ECN marked.
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* b) If the packet is a TCP packet, then we probabilistically call tcp_cwr
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* to reduce the congestion window. The current implementation uses a linear
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* distribution (0% probability at marking threshold, 100% probability
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* at drop threshold).
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* c) If the packet is not a TCP packet, then it is dropped.
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*
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* If the credit is below the drop threshold, the packet is dropped. If it
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* is a TCP packet, then it also calls tcp_cwr since packets dropped by
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* by a cgroup skb BPF program do not automatically trigger a call to
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* tcp_cwr in the current kernel code.
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*
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* This BPF program actually uses 2 drop thresholds, one threshold
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* for larger packets (>= 120 bytes) and another for smaller packets. This
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* protects smaller packets such as SYNs, ACKs, etc.
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*
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* The default bandwidth limit is set at 1Gbps but this can be changed by
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* a user program through a shared BPF map. In addition, by default this BPF
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* program does not limit connections using loopback. This behavior can be
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* overwritten by the user program. There is also an option to calculate
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* some statistics, such as percent of packets marked or dropped, which
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* a user program, such as hbm, can access.
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*/
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#include "hbm_kern.h"
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SEC("cgroup_skb/egress")
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int _hbm_out_cg(struct __sk_buff *skb)
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{
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long long delta = 0, delta_send;
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unsigned long long curtime, sendtime;
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struct hbm_queue_stats *qsp = NULL;
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unsigned int queue_index = 0;
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bool congestion_flag = false;
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bool ecn_ce_flag = false;
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struct hbm_pkt_info pkti = {};
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struct hbm_vqueue *qdp;
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bool drop_flag = false;
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bool cwr_flag = false;
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int len = skb->len;
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int rv = ALLOW_PKT;
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qsp = bpf_map_lookup_elem(&queue_stats, &queue_index);
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// Check if we should ignore loopback traffic
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if (qsp != NULL && !qsp->loopback && (skb->ifindex == 1))
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return ALLOW_PKT;
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hbm_get_pkt_info(skb, &pkti);
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// We may want to account for the length of headers in len
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// calculation, like ETH header + overhead, specially if it
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// is a gso packet. But I am not doing it right now.
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qdp = bpf_get_local_storage(&queue_state, 0);
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if (!qdp)
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return ALLOW_PKT;
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if (qdp->lasttime == 0)
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hbm_init_edt_vqueue(qdp, 1024);
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curtime = bpf_ktime_get_ns();
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// Begin critical section
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bpf_spin_lock(&qdp->lock);
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delta = qdp->lasttime - curtime;
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// bound bursts to 100us
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if (delta < -BURST_SIZE_NS) {
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// negative delta is a credit that allows bursts
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qdp->lasttime = curtime - BURST_SIZE_NS;
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delta = -BURST_SIZE_NS;
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}
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sendtime = qdp->lasttime;
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delta_send = BYTES_TO_NS(len, qdp->rate);
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__sync_add_and_fetch(&(qdp->lasttime), delta_send);
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bpf_spin_unlock(&qdp->lock);
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// End critical section
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// Set EDT of packet
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skb->tstamp = sendtime;
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// Check if we should update rate
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if (qsp != NULL && (qsp->rate * 128) != qdp->rate)
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qdp->rate = qsp->rate * 128;
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// Set flags (drop, congestion, cwr)
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// last packet will be sent in the future, bound latency
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if (delta > DROP_THRESH_NS || (delta > LARGE_PKT_DROP_THRESH_NS &&
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len > LARGE_PKT_THRESH)) {
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drop_flag = true;
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if (pkti.is_tcp && pkti.ecn == 0)
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cwr_flag = true;
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} else if (delta > MARK_THRESH_NS) {
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if (pkti.is_tcp)
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congestion_flag = true;
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else
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drop_flag = true;
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}
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if (congestion_flag) {
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if (bpf_skb_ecn_set_ce(skb)) {
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ecn_ce_flag = true;
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} else {
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if (pkti.is_tcp) {
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unsigned int rand = bpf_get_prandom_u32();
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if (delta >= MARK_THRESH_NS +
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(rand % MARK_REGION_SIZE_NS)) {
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// Do congestion control
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cwr_flag = true;
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}
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} else if (len > LARGE_PKT_THRESH) {
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// Problem if too many small packets?
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drop_flag = true;
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congestion_flag = false;
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}
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}
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}
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if (pkti.is_tcp && drop_flag && pkti.packets_out <= 1) {
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drop_flag = false;
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cwr_flag = true;
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congestion_flag = false;
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}
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if (qsp != NULL && qsp->no_cn)
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cwr_flag = false;
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hbm_update_stats(qsp, len, curtime, congestion_flag, drop_flag,
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cwr_flag, ecn_ce_flag, &pkti, (int) delta);
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if (drop_flag) {
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__sync_add_and_fetch(&(qdp->lasttime), -delta_send);
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rv = DROP_PKT;
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}
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if (cwr_flag)
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rv |= CWR;
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return rv;
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}
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char _license[] SEC("license") = "GPL";
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@ -29,6 +29,7 @@
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#define DROP_PKT 0
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#define ALLOW_PKT 1
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#define TCP_ECN_OK 1
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#define CWR 2
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#ifndef HBM_DEBUG // Define HBM_DEBUG to enable debugging
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#undef bpf_printk
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@ -45,8 +46,18 @@
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#define MAX_CREDIT (100 * MAX_BYTES_PER_PACKET)
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#define INIT_CREDIT (INITIAL_CREDIT_PACKETS * MAX_BYTES_PER_PACKET)
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// Time base accounting for fq's EDT
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#define BURST_SIZE_NS 100000 // 100us
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#define MARK_THRESH_NS 50000 // 50us
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#define DROP_THRESH_NS 500000 // 500us
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// Reserve 20us of queuing for small packets (less than 120 bytes)
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#define LARGE_PKT_DROP_THRESH_NS (DROP_THRESH_NS - 20000)
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#define MARK_REGION_SIZE_NS (LARGE_PKT_DROP_THRESH_NS - MARK_THRESH_NS)
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// rate in bytes per ns << 20
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#define CREDIT_PER_NS(delta, rate) ((((u64)(delta)) * (rate)) >> 20)
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#define BYTES_PER_NS(delta, rate) ((((u64)(delta)) * (rate)) >> 20)
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#define BYTES_TO_NS(bytes, rate) div64_u64(((u64)(bytes)) << 20, (u64)(rate))
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struct bpf_map_def SEC("maps") queue_state = {
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.type = BPF_MAP_TYPE_CGROUP_STORAGE,
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@ -67,6 +78,7 @@ BPF_ANNOTATE_KV_PAIR(queue_stats, int, struct hbm_queue_stats);
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struct hbm_pkt_info {
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int cwnd;
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int rtt;
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int packets_out;
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bool is_ip;
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bool is_tcp;
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short ecn;
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@ -86,16 +98,20 @@ static int get_tcp_info(struct __sk_buff *skb, struct hbm_pkt_info *pkti)
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if (tp) {
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pkti->cwnd = tp->snd_cwnd;
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pkti->rtt = tp->srtt_us >> 3;
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pkti->packets_out = tp->packets_out;
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return 0;
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}
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}
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}
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}
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pkti->cwnd = 0;
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pkti->rtt = 0;
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pkti->packets_out = 0;
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return 1;
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}
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static __always_inline void hbm_get_pkt_info(struct __sk_buff *skb,
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struct hbm_pkt_info *pkti)
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static void hbm_get_pkt_info(struct __sk_buff *skb,
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struct hbm_pkt_info *pkti)
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{
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struct iphdr iph;
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struct ipv6hdr *ip6h;
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@ -123,10 +139,22 @@ static __always_inline void hbm_get_pkt_info(struct __sk_buff *skb,
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static __always_inline void hbm_init_vqueue(struct hbm_vqueue *qdp, int rate)
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{
|
||||
bpf_printk("Initializing queue_state, rate:%d\n", rate * 128);
|
||||
qdp->lasttime = bpf_ktime_get_ns();
|
||||
qdp->credit = INIT_CREDIT;
|
||||
qdp->rate = rate * 128;
|
||||
bpf_printk("Initializing queue_state, rate:%d\n", rate * 128);
|
||||
qdp->lasttime = bpf_ktime_get_ns();
|
||||
qdp->credit = INIT_CREDIT;
|
||||
qdp->rate = rate * 128;
|
||||
}
|
||||
|
||||
static __always_inline void hbm_init_edt_vqueue(struct hbm_vqueue *qdp,
|
||||
int rate)
|
||||
{
|
||||
unsigned long long curtime;
|
||||
|
||||
curtime = bpf_ktime_get_ns();
|
||||
bpf_printk("Initializing queue_state, rate:%d\n", rate * 128);
|
||||
qdp->lasttime = curtime - BURST_SIZE_NS; // support initial burst
|
||||
qdp->credit = 0; // not used
|
||||
qdp->rate = rate * 128;
|
||||
}
|
||||
|
||||
static __always_inline void hbm_update_stats(struct hbm_queue_stats *qsp,
|
||||
|
|
|
|||
Loading…
Reference in New Issue