5.1.1.3. Batching

The BATCH QoS Policy can be used to decrease the amount of communication overhead associated with the transmission and (in the case of reliable communication) acknowledgment of small DDS samples, in order to increase throughput. It does this by collecting multiple user data DDS samples to be sent in a single network packet, to take advantage of the efficiency of sending larger packets.

Batching increases effective throughput dramatically for small data DDS samples. Throughput for small DDS samples is typically limited by CPU capacity and not by network bandwidth. Batching many smaller DDS samples to be sent in a single large packet increases network utilization and thus throughput in terms of DDS samples per second.

For more information, see BATCH QosPolicy, in the RTI Connext Core Libraries User’s Manual.

The tests below show how powerful the use of batching can be. In these tests, we compare the RTI Perftest default configuration for throughput, which enables batching (with a batch size of 8192 bytes), and a configuration where batching is disabled.

Note

We choose 8192 bytes for the batch size because it is the closest power of two below the maximum MTU that can be configured for a regular NIC, which is 9000 bytes. This way the RTPS packet doesn’t need to be fragmented.

This configuration, by itself, cannot ensure that the packet will not be fragmented, since if the MTU of the NIC is set to a lower value (like the default value in many NICs, of 1500 bytes), then the packet will have fragmentation.

Note

Since some samples are delayed until the batch is ready, you may observe increased latency. The maximum delay, as well as maximum bytes or maximum number of samples, can be configured. See BATCH QosPolicy, in the RTI Connext Core Libraries User’s Manual.

Unkeyed, UDPv4 10Gbps Network, C++98

Linux x64

Maximum Throughput

The graph below shows the expected throughput behavior when performing a 1-1 communication between two Linux nodes in a 10Gbps network with and without batching (with a batch size of 8192 bytes). The numbers are for best-effort as well as strict reliable reliability scenarios.

Detailed Statistics

This table contains the raw numbers presented by RTI Perftest. These numbers are the exact output with no further processing.

• Best Effort, Batching

Sample Size (Bytes)	Total Samples	Avg Samples/s	Avg Mbps	Lost Samples	Lost Samples (%)
32	96567174	4822939	1234.7	133888	0.14
64	88277933	4408632	2257.2	0	0.00
128	78236376	3907863	4001.7	0	0.00
256	61245120	3057756	6262.3	0	0.00
512	43312848	2162371	8857.1	0	0.00
1024	23817335	1190128	9749.5	0	0.00
2048	11952159	597348	9787.0	0	0.00
4096	5987406	299257	9806.1	0	0.00
8192	3006174	150276	9848.5	0	0.00
16384	1509068	75446	9888.9	34	0.00
32768	756015	37798	9908.7	8	0.00
63000	393520	19675	9916.3	4	0.00

• Best Effort, No Batching

Sample Size (Bytes)	Total Samples	Avg Samples/s	Avg Mbps	Lost Samples	Lost Samples (%)
32	7151957	357088	91.4	0	0.00
64	7212591	360136	184.4	0	0.00
128	7155745	357257	365.8	0	0.00
256	7308831	364906	747.3	0	0.00
512	7196016	359271	1471.6	0	0.00
1024	6941380	346546	2838.9	0	0.00
2048	6588215	328958	5389.7	0	0.00
4096	5882497	293700	9624.0	0	0.00
8192	3006153	150276	9848.5	0	0.00
16384	1509068	75446	9889.0	43	0.00
32768	756071	37800	9909.3	9	0.00
63000	393520	19675	9916.3	5	0.00

• Reliable, Batching

Sample Size (Bytes)	Total Samples	Avg Samples/s	Avg Mbps	Lost Samples	Lost Samples (%)
32	92191882	4603759	1178.6	0	0.00
64	82246912	4106899	2102.7	0	0.00
128	69599190	3476168	3559.6	0	0.00
256	52012088	2597675	5320.0	0	0.00
512	34342828	1715328	7026.0	0	0.00
1024	20394416	1018645	8344.7	0	0.00
2048	11496140	574177	9407.3	0	0.00
4096	5979302	298635	9785.7	0	0.00
8192	3004618	150185	9842.6	0	0.00
16384	1508831	75431	9887.0	0	0.00
32768	756045	37797	9908.3	0	0.00
63000	393539	19674	9915.8	0	0.00
100000	247582	12376	9901.5	0	0.00
500000	46851	2340	9361.4	0	0.00
1048576	15904	792	6652.0	0	0.00
1548576	14951	746	9253.7	0	0.00
4194304	5116	255	8569.6	0	0.00
10485760	2069	103	8678.7	0	0.00

• Reliable, No Batching

Sample Size (Bytes)	Total Samples	Avg Samples/s	Avg Mbps	Lost Samples	Lost Samples (%)
32	4295545	214612	54.9	0	0.00
64	4445516	222139	113.7	0	0.00
128	4448833	222331	227.7	0	0.00
256	4508238	225308	461.4	0	0.00
512	4496387	224749	920.6	0	0.00
1024	4397735	219822	1800.8	0	0.00
2048	4269910	213436	3496.9	0	0.00
4096	3991218	199497	6537.1	0	0.00
8192	3005200	150213	9844.4	0	0.00
16384	1508834	75432	9887.0	0	0.00
32768	756054	37797	9908.3	0	0.00
63000	393539	19674	9915.8	0	0.00

Perftest Scripts

To produce these tests, we executed RTI Perftest for C++98. The exact script used can be found here:

#!/bin/bash
filename=$0
script_location=$(cd "$(dirname "$filename")" || exit 255; pwd)

export datasizes="32 64 128 256 512 1024 2048 4096 8192 16384 32768 63000"
export datasizes_extended="${datasizes} 100000 500000 1048576 1548576 4194304 10485760"

export domain="2"
export exec_time=20
export num_reps=1
export instance_number=100000
export core=0

# We will use some colors to improve visibility of errors and info messages.
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
BLUE='\033[0;34m'
LIGHTBLUE='\033[0;36m'
NC='\033[0m'
INFO_TAG="${GREEN}[INFO]:${NC}"
WARNING_TAG="${YELLOW}[WARNING]:${NC}"
ERROR_TAG="${RED}[ERROR]:${NC}"

export ip_machine_1="10.2.78.20"
export ip_machine_2="10.2.78.21"
export if10Gbps="enp1s0f0"
export if1Gbps="eno1"

################################################################################

function disable_colors() {
    export RED=""
    export GREEN=""
    export YELLOW=""
    export NC=""
    export BLUE=""
    export LIGHTBLUE=""
    export INFO_TAG="${GREEN}[INFO]:${NC}"
    export WARNING_TAG="${YELLOW}[WARNING]:${NC}"
    export ERROR_TAG="${RED}[ERROR]:${NC}"
}

function change_domain() {
    if [[ "$domain" == "1" ]]; then
        export domain="2"
    else
        export domain="1"
    fi
}

# Usage: execute_test <keyed/unkeyed> <rel/be> <datasizes> <batchSize>
function execute_test() {

    local keyed_unkeyed=$1
    local rel_be=$2
    local datasizes_test=$3
    local other_args=$4
    local name_suffix=$5

    local commands_string_test=$commands_string
    local tag=""

    if [[ "${keyed_unkeyed}" == "keyed" ]]; then
        commands_string_test="${commands_string_test} -keyed -instances $instance_number"
        tag="[${YELLOW}${transport}${NC}|${BLUE}K${NC}|"
    else
        tag="[${YELLOW}${transport}${NC}|${LIGHTBLUE}UK${NC}|"
    fi

    if [[ "${rel_be}" == "be" ]]; then
        commands_string_test="${commands_string_test} -bestEffort"
        tag="${tag}${YELLOW}BE${NC}]"
    else
        tag="${tag}${RED}REL${NC}]"
    fi

    tag="${tag}[${LIGHTBLUE}${lat_thr}${NC}]"

    local output_file=$output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}.csv

    if [[ "$role" == "pub" ]]; then
        echo -e "${YELLOW}[TEST]: $keyed_unkeyed, $rel_be. ${NC}"
    fi

    if [[ "$NO_TASKSET" == "" ]]; then
        if [[ "$LANGUAGE" != "java" && "$LANGUAGE" != "cs" ]]; then
            export pre_command_string="taskset -c $core"
        fi
    fi

    if [[ "$LANGUAGE" == "python" ]]; then
        export pre_command_string="python3 "
    fi

    if [[ "$DOCKER" == "1" ]]; then
        export pre_command_string="taskset -c $core docker run --net=host -v /home/perfuser/rti_license_connextpro.dat:/opt/rti.com/rti_connext_dds-7.3.0/rti_license.dat rticom/perftest:7.3.0-EAR "
        executable=""
    fi

    # Get the aprox time this will take:
    total_tests=$((`wc -w <<< "$datasizes_test"` * num_reps))
    total_time=$((total_tests * exec_time))

    touch $output_file
    local no_headers=""
    local current_test=0
    for index in $(seq 1 ${num_reps}); do
        for DATALEN in ${datasizes_test}; do
            current_test=$((current_test + 1))
            export command="$pre_command_string $executable -domain $domain -dataLen $DATALEN $commands_string_test $other_args $no_headers"
            if [[ "$role" == "pub" ]]; then
                echo -e "Test ${tag} (${current_test}/${total_tests}) -- Total time = ${total_time}s"
                echo -e ${BLUE}$command${NC}
            else
                echo -e ${LIGHTBLUE}$command${NC}
            fi
            if [[ "$LANGUAGE" == "cs" && "$role" == "pub" ]]; then
                sleep 3
            fi
            if [[ "$raw" == "1" && "$role" == "sub" ]]; then
                sleep 5
            fi
            if [[ "${get_netstat_info}" == "1" ]]; then
                echo -e "${INFO_TAG} Getting netstat info before"
                netstat -s -u | grep -e "error" -e "packet" > $output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat_before.txt
            fi
            eval $command >> $output_file;
            if [[ "${get_netstat_info}" == "1" ]]; then
                echo -e "${INFO_TAG} Getting netstat info after"
                netstat -s -u | grep -e "error" -e "packet" > $output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat_after.txt
                touch "$output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat.csv"
                python3 $script_location/../../../tools/diff_netstat_output.py \
                    -n $output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat_after.txt \
                    -o $output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat_before.txt \
                    -d $DATALEN $no_header_netstat \
                    -csv >> "$output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat.csv"
                rm -rf $output_folder/${lat_thr}_${role}_${keyed_unkeyed}_${rel_be}${name_suffix}_netstat_*.txt
                no_header_netstat=" -nh"
            fi
            no_headers=" -noOutputHeaders"

            change_domain
        done
    done
}

################################################################################
# PARSE COMMAND LINE OPTIONS:

while [ "$1" != "" ]; do
    case $1 in
        --executable)
            executable=$2
            shift
            ;;
        --docker)
            DOCKER="1"
            ;;
        --output-folder)
            output_folder=$2
            shift
            ;;
        --sub-folder)
            sub_folder=$2
            shift
            ;;
        --role)
            export role=$2
            shift
            ;;
        --core)
            export core=$2
            shift
            ;;
        --test-kind)
            export lat_thr=$2
            shift
            ;;
        --interface1)
            export interface=$2
            shift
            ;;
        --interface2)
            export interface2=$2
            shift
            ;;
        --ip1)
            export ip1=$2
            shift
            ;;
        --ip2)
            export ip2=$2
            shift
            ;;
        --repetitions)
            export num_reps=$2
            shift
            ;;
        --domain)
            export domain=$2
            shift
            ;;
        --execution-time)
            export exec_time=$2
            shift
            ;;
        --transport)
            export transport=$2
            shift
            ;;
        --datalen)
            export datalen_input=$2
            shift
            ;;
        --file-suffix)
            export file_suffix=$2
            shift
            ;;
        --executable-suffix)
            export executable_suffix=$2
            shift
            ;;
        --extra-arguments)
            export extra_arguments=$2
            shift
            ;;
        --extra-arguments-pub)
            export extra_arguments_pub=$2
            shift
            ;;
        --extra-arguments-sub)
            export extra_arguments_sub=$2
            shift
            ;;
        --skip-no-batching)
            export skip_no_batching="1"
            ;;
        --skip-be)
            export skip_be_tests="1"
            ;;
        --skip-rel)
            export skip_rel_tests="1"
            ;;
        --skip-keyed)
            export skip_keyed_data="1"
            ;;
        --skip-large-data)
            export skip_large_data="1"
            ;;
        --large-data)
            export large_data="1"
            ;;
        --keyed)
            export skip_unkeyed="1"
            ;;
        --unkeyed)
            export skip_keyed_data="1"
            ;;
        --no-batching | --skip-batching)
            export no_batching_only="1"
            ;;
        --reliable)
            export skip_be_tests="1"
            ;;
        --best-effort)
            export skip_rel_tests="1"
            ;;
        --security)
            export security_only="$2"
            shift
            ;;
        --micro)
            export micro="1"
            ;;
        --raw | --raw-transport)
            export raw="1"
            ;;
        --tss)
            export tss="1"
            ;;
        --no-colors)
            export NO_COLORS="1"
            ;;
        --language)
            export LANGUAGE=$2
            shift
            ;;
        --loss-rate)
            export loss_rate=$2
            shift
            ;;
        --get-netstat-info | --netstat)
            export get_netstat_info="1"
            ;;
        --no-taskset)
            export NO_TASKSET="1"
            ;;
        *)
            echo -e "unknown parameter \"$1\""
            exit 255
            ;;
    esac
    shift
done

if [[ "$NO_COLORS" == "1" ]]; then
    disable_colors
fi

export folder_base="$(dirname "${executable}")"/../../..

if [[ $LANGUAGE == "java"  || "$LANGUAGE" == "cs" ]]; then
    export folder_base="$(dirname "${executable}")"/../..
fi
if [[ $tss == "1" ]]; then
    export folder_base="$(dirname "${executable}")"/../../../../..
fi

if [[ "${executable_suffix}" != "" ]]; then
    export executable="${executable}${executable_suffix}"
fi

if [[ "${sub_folder}" != "" ]]; then
    export output_folder="${output_folder}/${sub_folder}"
fi

echo -e "${INFO_TAG} Perftest executable is: $executable"
echo -e "${INFO_TAG} Output folder is: $output_folder"

################################################################################

if [[ "$LANGUAGE" == "python" ]]; then
    export skip_keyed_data="1"
    export skip_large_data="1"
    export skip_be_tests="1"
    export skip_no_batching="1"
fi

if [[ "${skip_large_data}" == "1" ]]; then
    export datasizes_extended=${datasizes}
elif [[ "${large_data}" == "1" ]]; then
    export datasizes=${datasizes_extended}
fi

if [[ "${datalen_input}" != "" ]]; then
    echo -e "${YELLOW}[TEST] Testing only for ${datalen_input}${NC}"
    export datasizes=${datalen_input}
    export datasizes_extended=${datalen_input}
    if [[ "${no_batching_only}" != "1" ]]; then
        export skip_large_data="1"
    fi
fi

if [[ "$role" != "pub" && "$role" != "sub" ]]; then
    echo -e "${ERROR_TAG} It must be either publisher or subscriber"
    exit 255
fi

if [[ "$lat_thr" != "thr" && "$lat_thr" != "lat" ]]; then
    echo -e "${ERROR_TAG} It must be either lat or thr"
    exit 255
fi

if [[ "${interface}" == "" ]]; then
    echo "Using default nics"
    export nic_publisher=${ip_machine_1}
    export nic_subscriber=${ip_machine_2}
elif [[ "${interface}" == "both" ]]; then
    export nic_publisher="enp1s0f0,eno1"
    export nic_subscriber="enp1s0f0,eno1"
    echo -e "${INFO_TAG} Using nic_publisher: ${nic_publisher}"
    echo -e "${INFO_TAG} Using nic_subscriber: ${nic_subscriber}"
else
    export nic_publisher=$interface
    echo -e "${INFO_TAG} Using nic_publisher: ${nic_publisher}"

    if [[ "${interface2}" == "" ]]; then
        export nic_subscriber=$interface
    else
        export nic_subscriber=$interface2
    fi
    echo -e "${INFO_TAG} Using nic_subscriber: ${nic_subscriber}"

    if [[ "${ip1}" != "" ]]; then
        export ip_publisher=$ip1
        echo "Using ip_publisher: ${ip_publisher}"
    fi

    if [[ "${ip2}" != "" ]]; then
        export ip_subscriber=$ip2
        echo "Using ip_subscriber: ${ip_subscriber}"
    fi

fi

export transport_string="-transport $transport"

if [[ "$transport" == "UDPv4" ]]; then

    export transport_string_pub="$transport_string -nic $nic_publisher"
    export transport_string_sub="$transport_string -nic $nic_subscriber"

    if [[ "$micro" == "1" || "$raw" == "1" ]]; then
        export transport_string_pub="$transport_string_pub -peer ${ip_subscriber}"
        export transport_string_sub="$transport_string_sub -peer ${ip_publisher}"
    fi

elif [[ "$transport" == "TCP" ]]; then
    export transport_string_pub="$transport_string \
        -nic $nic_publisher \
        -peer 0@tcpv4_lan://${ip_subscriber}:7400"
    export transport_string_sub="$transport_string \
        -nic $nic_subscriber \
        -peer 0@tcpv4_lan://${ip_publisher}:7400"
elif [[ "$transport" == "TLS" ]]; then
    export transport_string_pub="$transport_string \
        -nic $nic_publisher \
        -peer tlsv4_lan://${ip_subscriber}:7400"
    export transport_string_sub="$transport_string \
        -nic $nic_subscriber \
        -peer tlsv4_lan://${ip_publisher}:7400"
elif [[ "$transport" == "UDPv4_WAN" ]]; then
    export transport_string_pub="$transport_string \
        -nic $nic_publisher \
        -transportPublicAddress $ip_publisher:7400"
    export transport_string_sub="$transport_string \
        -nic $nic_subscriber \
        -peer 0@udpv4_wan://${ip_publisher}:7400"
else
    export transport_string_pub="$transport_string"
    export transport_string_sub="$transport_string"
fi

################################################################################

export pub_string="-pub \
        ${transport_string_pub} \
        -noPrintIntervals \
        -executionTime $exec_time"

if [[ ${lat_thr} == "lat" ]]; then
    export pub_string="$pub_string \
        -latencyTest"
fi

export sub_string="-sub \
        ${transport_string_sub} \
        -noPrintIntervals"

if [[ "$role" == "pub" ]]; then
    echo -e "$INFO_TAG Publisher side running"
    export commands_string=${pub_string}
    export extra_arguments="${extra_arguments} ${extra_arguments_pub}"
else
    echo -e "$INFO_TAG Subscriber side running"
    export commands_string=${sub_string}
    export extra_arguments="${extra_arguments} ${extra_arguments_sub}"
fi

###############################################################################

echo -e "${INFO_TAG} Executing: /set_${lat_thr}_mode.sh"
sudo /set_${lat_thr}_mode.sh
sleep 5

echo -e "${INFO_TAG} Disabling any loss rate"
sudo tc qdisc add dev $nic_publisher root netem loss 0%
sudo tc qdisc del dev $nic_publisher root netem loss 0%

if [[ "$role" == "pub" && "${loss_rate}" != "" ]]; then
    echo -e "${INFO_TAG} Setting loss rate to ${loss_rate}%"
    sudo tc qdisc add dev $nic_publisher root netem loss $loss_rate%
fi

cd $folder_base
echo -e "${INFO_TAG} Folder Base is: $PWD"
mkdir -p $output_folder

# Tests that may use batching (when doing throughput tests)
if [[ ${no_batching_only} != "1" ]]; then

    # UNKEYED
    if [[ "${skip_unkeyed}" == "" ]]; then

        # RELIABLE
        if [[ "${skip_rel_tests}" == "" ]]; then
            execute_test "unkeyed" "rel" "${datasizes_extended}" "${extra_arguments}" "$file_suffix"
        fi

        # BEST EFFORT
        if [[ "${skip_be_tests}" == "" ]]; then
            execute_test "unkeyed" "be" "${datasizes}" "${extra_arguments}" "$file_suffix"
        fi
    fi

    # KEYED
    if [[ "${skip_keyed_data}" == "" ]]; then

        # RELIABLE
        if [[ "${skip_rel_tests}" == "" ]]; then
            execute_test "keyed" "rel" "${datasizes}" "${extra_arguments}" "$file_suffix"
        fi

        # BEST EFFORT
        if [[ "${skip_be_tests}" == "" ]]; then
            execute_test "keyed" "be" "${datasizes}" "${extra_arguments}" "$file_suffix"
        fi
    fi

fi

if [[ "${skip_no_batching}" == "" || "${no_batching_only}" == "1" ]]; then
    no_batching_tests="1"
fi

# Tests that will not use batching
if [[ "${lat_thr}" == "thr" && "${no_batching_tests}" == "1" ]]; then

    if [[ "$role" == "pub" ]]; then
        export commands_string="${commands_string} -batchSize 0"
    fi

    # UNKEYED
    if [[ "${skip_unkeyed}" == "" ]]; then

        # RELIABLE
        if [[ "${skip_rel_tests}" == "" ]]; then
            execute_test "unkeyed" "rel" "${datasizes}" "${extra_arguments}" "_noBatch${file_suffix}"
        fi

        # BEST EFFORT
        if [[ "${skip_be_tests}" == "" ]]; then
            execute_test "unkeyed" "be" "${datasizes}" "${extra_arguments}" "_noBatch${file_suffix}"
        fi
    fi
fi

if [[ "$role" == "pub" && "${loss_rate}" != "" ]]; then
    echo -e "${INFO_TAG} Disabling loss rate"
    sudo tc qdisc del dev $nic_publisher root netem loss $loss_rate%
fi

#!/bin/bash
filename=$0
script_location=$(cd "$(dirname "$filename")" || exit 255; pwd)

echo -e "[Calling base_script/script.sh]"
"${script_location}/../base_script/script.sh" $@ --transport UDPv4

Test Hardware

The following hardware was used to perform these tests:

Linux Nodes

Dell R340 Servers (13 Units)
Processor: Intel Xeon E-2278G (3.4-5GHz, 8c/16t, 16MB cache, 2 memory channels @2666MHz)
RAM: 4x 16GB 2666MHz DIMM (64GB RAM)
HD: 480GB SATA SSD
NIC 1: Intel 710 dual port 10Gbps SFP
OS: Ubuntu 20.04 -- gcc 9.3.0

Switch

Dell 2048 -- 10Gbps switch (10Gbps and 1Gbps interfaces)