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    SubjectCFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinned
    Hi All,

    In our test environment, while testing the CFS Bandwidth V6 patch set
    on top of 55922c9d1b84. We observed that the CPU's idle time is seen
    between 30% to 40% while running CPU bound test, with the cgroups tasks
    not pinned to the CPU's. Whereas in the inverse case, where the cgroups
    tasks are pinned to the CPU's, the idle time seen is nearly zero.

    Test Scenario
    --------------
    - 5 cgroups are created with each groups assigned 2, 2, 4, 8, 16 tasks respectively.
    - Each of the cgroup, has N sub-cgroups created. Where N is the NR_TASKS the cgroup
    is assigned with. i.e., cgroup1, will create two sub-cgroups under it and assigned
    one tasks per sub-group.
    ------------
    | cgroup 1 |
    ------------
    / \
    / \
    -------------- --------------
    |sub-cgroup 1| |sub-cgroup 2|
    | (task 1) | | (task 2) |
    -------------- --------------
    - Top cgroup is given unlimited quota (cpu.cfs_quota_us = -1) and period of 500ms
    (cpu.cfs_period_us = 500000). Whereas the sub-cgroups are given 250ms of quota
    (cpu.cfs_quota_us = 250000) and period of 500ms. i.e. the top cgroups are given
    unlimited bandwidth, whereas the sub-group are throttled every 250ms.
    - Additional if required the proportional CPU shares can be assigned to cpu.shares
    as NR_TASKS * 1024. i.e. cgroup1 has 2 tasks * 1024 = 2048 worth cpu.shares
    for cgroup1. (In the below test results published all cgroups and sub-cgroups
    are given the equal share of 1024).

    - One CPU bound while(1) task is attached to each sub-cgroup.
    - sum-exec time for each cgroup/sub-cgroup is captured from /proc/sched_debug after
    60 seconds and analyzed for the run time of the tasks a.k.a sub-cgroup.

    How is the idle CPU time measured ?
    ------------------------------------
    - vmstat stats are logged every 2 seconds, after attaching the last while1 task
    to 16th sub-cgroup of cgroup 5 till the 60 sec run is over. After the run idle%
    of a CPU is calculated by summing idle column from the vmstat log and dividing it
    by number of samples collected, of-course after neglecting the first record
    from the log.
    How are the tasks pinned to the CPU ?
    -------------------------------------
    - cgroup is mounted with cpuset,cpu controller and for every 2 sub-cgroups one
    physical CPU is allocated. i.e. CPU 1 is allocated between 1/1 and 1/2 (Group 1,
    sub-cgroup 1 and sub-cgroup 2). Similarly CPUs 7 to 15 are allocated to 15/1 to
    15/16 (Group 15, subgroup 1 to 16). Note that test machine used to test has
    16 CPUs.
    Result for non-pining case
    ---------------------------
    Only the hierarchy is created as stated above and cpusets are not assigned per cgroup.
    Average CPU Idle percentage 34.8% (as explained above in the Idle time measured)
    Bandwidth shared with remaining non-Idle 65.2%

    * Note: For the sake of roundoff value the numbers are multiplied by 100.

    In the below result for cgroup1 9.2500 corresponds to sum-exec time captured
    from /proc/sched_debug for cgroup 1 tasks (including sub-cgroup 1 and 2).
    Which is in-turn 6% of the non-Idle CPU time (which is derived by 9.2500 * 65.2 / 100 )

    Bandwidth of Group 1 = 9.2500 i.e = 6.0300% of non-Idle CPU time 65.2%
    |...... subgroup 1/1 = 48.7800 i.e = 2.9400% of 6.0300% Groups non-Idle CPU time
    |...... subgroup 1/2 = 51.2100 i.e = 3.0800% of 6.0300% Groups non-Idle CPU time


    Bandwidth of Group 2 = 9.0400 i.e = 5.8900% of non-Idle CPU time 65.2%
    |...... subgroup 2/1 = 51.0200 i.e = 3.0000% of 5.8900% Groups non-Idle CPU time
    |...... subgroup 2/2 = 48.9700 i.e = 2.8800% of 5.8900% Groups non-Idle CPU time


    Bandwidth of Group 3 = 16.9300 i.e = 11.0300% of non-Idle CPU time 65.2%
    |...... subgroup 3/1 = 26.0300 i.e = 2.8700% of 11.0300% Groups non-Idle CPU time
    |...... subgroup 3/2 = 25.8800 i.e = 2.8500% of 11.0300% Groups non-Idle CPU time
    |...... subgroup 3/3 = 22.7800 i.e = 2.5100% of 11.0300% Groups non-Idle CPU time
    |...... subgroup 3/4 = 25.2900 i.e = 2.7800% of 11.0300% Groups non-Idle CPU time


    Bandwidth of Group 4 = 27.9300 i.e = 18.2100% of non-Idle CPU time 65.2%
    |...... subgroup 4/1 = 16.6000 i.e = 3.0200% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/2 = 8.0000 i.e = 1.4500% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/3 = 9.0000 i.e = 1.6300% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/4 = 7.9600 i.e = 1.4400% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/5 = 12.3500 i.e = 2.2400% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/6 = 16.2500 i.e = 2.9500% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/7 = 12.6100 i.e = 2.2900% of 18.2100% Groups non-Idle CPU time
    |...... subgroup 4/8 = 17.1900 i.e = 3.1300% of 18.2100% Groups non-Idle CPU time


    Bandwidth of Group 5 = 36.8300 i.e = 24.0100% of non-Idle CPU time 65.2%
    |...... subgroup 5/1 = 56.6900 i.e = 13.6100% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/2 = 8.8600 i.e = 2.1200% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/3 = 5.5100 i.e = 1.3200% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/4 = 4.5700 i.e = 1.0900% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/5 = 7.9500 i.e = 1.9000% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/6 = 2.1600 i.e = .5100% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/7 = 2.3400 i.e = .5600% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/8 = 2.1500 i.e = .5100% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/9 = 9.7200 i.e = 2.3300% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/10 = 5.0600 i.e = 1.2100% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/11 = 4.6900 i.e = 1.1200% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/12 = 8.9700 i.e = 2.1500% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/13 = 8.4600 i.e = 2.0300% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/14 = 11.8400 i.e = 2.8400% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/15 = 6.3400 i.e = 1.5200% of 24.0100% Groups non-Idle CPU time
    |...... subgroup 5/16 = 5.1500 i.e = 1.2300% of 24.0100% Groups non-Idle CPU time

    Pinned case
    --------------
    CPU hierarchy is created and cpusets are allocated.
    Average CPU Idle percentage 0%
    Bandwidth shared with remaining non-Idle 100%

    Bandwidth of Group 1 = 6.3400 i.e = 6.3400% of non-Idle CPU time 100%
    |...... subgroup 1/1 = 50.0400 i.e = 3.1700% of 6.3400% Groups non-Idle CPU time
    |...... subgroup 1/2 = 49.9500 i.e = 3.1600% of 6.3400% Groups non-Idle CPU time


    Bandwidth of Group 2 = 6.3200 i.e = 6.3200% of non-Idle CPU time 100%
    |...... subgroup 2/1 = 50.0400 i.e = 3.1600% of 6.3200% Groups non-Idle CPU time
    |...... subgroup 2/2 = 49.9500 i.e = 3.1500% of 6.3200% Groups non-Idle CPU time


    Bandwidth of Group 3 = 12.6300 i.e = 12.6300% of non-Idle CPU time 100%
    |...... subgroup 3/1 = 25.0300 i.e = 3.1600% of 12.6300% Groups non-Idle CPU time
    |...... subgroup 3/2 = 25.0100 i.e = 3.1500% of 12.6300% Groups non-Idle CPU time
    |...... subgroup 3/3 = 25.0000 i.e = 3.1500% of 12.6300% Groups non-Idle CPU time
    |...... subgroup 3/4 = 24.9400 i.e = 3.1400% of 12.6300% Groups non-Idle CPU time


    Bandwidth of Group 4 = 25.1000 i.e = 25.1000% of non-Idle CPU time 100%
    |...... subgroup 4/1 = 12.5400 i.e = 3.1400% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/2 = 12.5100 i.e = 3.1400% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/3 = 12.5300 i.e = 3.1400% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/4 = 12.5000 i.e = 3.1300% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/5 = 12.4900 i.e = 3.1300% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/6 = 12.4700 i.e = 3.1200% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/7 = 12.4700 i.e = 3.1200% of 25.1000% Groups non-Idle CPU time
    |...... subgroup 4/8 = 12.4500 i.e = 3.1200% of 25.1000% Groups non-Idle CPU time


    Bandwidth of Group 5 = 49.5700 i.e = 49.5700% of non-Idle CPU time 100%
    |...... subgroup 5/1 = 49.8500 i.e = 24.7100% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/2 = 6.2900 i.e = 3.1100% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/3 = 6.2800 i.e = 3.1100% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/4 = 6.2700 i.e = 3.1000% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/5 = 6.2700 i.e = 3.1000% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/6 = 6.2600 i.e = 3.1000% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/7 = 6.2500 i.e = 3.0900% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/8 = 6.2400 i.e = 3.0900% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/9 = 6.2400 i.e = 3.0900% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/10 = 6.2300 i.e = 3.0800% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/11 = 6.2300 i.e = 3.0800% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/12 = 6.2200 i.e = 3.0800% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/13 = 6.2100 i.e = 3.0700% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/14 = 6.2100 i.e = 3.0700% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/15 = 6.2100 i.e = 3.0700% of 49.5700% Groups non-Idle CPU time
    |...... subgroup 5/16 = 6.2100 i.e = 3.0700% of 49.5700% Groups non-Idle CPU time

    with equal cpu shares allocated to all the groups/sub-cgroups and CFS bandwidth configured
    to allow 100% CPU utilization. We see the CPU idle time in the un-pinned case.

    Benchmark used to reproduce the issue, is attached. Justing executing the script should
    report similar numbers.

    #!/bin/bash

    NR_TASKS1=2
    NR_TASKS2=2
    NR_TASKS3=4
    NR_TASKS4=8
    NR_TASKS5=16

    BANDWIDTH=1
    SUBGROUP=1
    PRO_SHARES=0
    MOUNT=/cgroup/
    LOAD=/root/while1

    usage()
    {
    echo "Usage $0: [-b 0|1] [-s 0|1] [-p 0|1]"
    echo "-b 1|0 set/unset Cgroups bandwidth control (default set)"
    echo "-s Create sub-groups for every task (default creates sub-group)"
    echo "-p create propotional shares based on cpus"
    exit
    }
    while getopts ":b:s:p:" arg
    do
    case $arg in
    b)
    BANDWIDTH=$OPTARG
    shift
    if [ $BANDWIDTH -gt 1 ] && [ $BANDWIDTH -lt 0 ]
    then
    usage
    fi
    ;;
    s)
    SUBGROUP=$OPTARG
    shift
    if [ $SUBGROUP -gt 1 ] && [ $SUBGROUP -lt 0 ]
    then
    usage
    fi
    ;;
    p)
    PRO_SHARES=$OPTARG
    shift
    if [ $PRO_SHARES -gt 1 ] && [ $PRO_SHARES -lt 0 ]
    then
    usage
    fi
    ;;
    *)

    esac
    done
    if [ ! -d $MOUNT ]
    then
    mkdir -p $MOUNT
    fi
    test()
    {
    echo -n "[ "
    if [ $1 -eq 0 ]
    then
    echo -ne '\E[42;40mOk'
    else
    echo -ne '\E[31;40mFailed'
    tput sgr0
    echo " ]"
    exit
    fi
    tput sgr0
    echo " ]"
    }
    mount_cgrp()
    {
    echo -n "Mounting root cgroup "
    mount -t cgroup -ocpu,cpuset,cpuacct none $MOUNT &> /dev/null
    test $?
    }
    umount_cgrp()
    {
    echo -n "Unmounting root cgroup "
    cd /root/
    umount $MOUNT
    test $?
    }
    create_hierarchy()
    {
    mount_cgrp
    cpuset_mem=`cat $MOUNT/cpuset.mems`
    cpuset_cpu=`cat $MOUNT/cpuset.cpus`
    echo -n "creating groups/sub-groups ..."
    for (( i=1; i<=5; i++ ))
    do
    mkdir $MOUNT/$i
    echo $cpuset_mem > $MOUNT/$i/cpuset.mems
    echo $cpuset_cpu > $MOUNT/$i/cpuset.cpus
    echo -n ".."
    if [ $SUBGROUP -eq 1 ]
    then
    jj=$(eval echo "\$NR_TASKS$i")
    for (( j=1; j<=$jj; j++ ))
    do
    mkdir -p $MOUNT/$i/$j
    echo $cpuset_mem > $MOUNT/$i/$j/cpuset.mems
    echo $cpuset_cpu > $MOUNT/$i/$j/cpuset.cpus
    echo -n ".."
    done
    fi
    done
    echo "."
    }
    cleanup()
    {
    pkill -9 while1 &> /dev/null
    sleep 10
    echo -n "Umount groups/sub-groups .."
    for (( i=1; i<=5; i++ ))
    do
    if [ $SUBGROUP -eq 1 ]
    then
    jj=$(eval echo "\$NR_TASKS$i")
    for (( j=1; j<=$jj; j++ ))
    do
    rmdir $MOUNT/$i/$j
    echo -n ".."
    done
    fi
    rmdir $MOUNT/$i
    echo -n ".."
    done
    echo " "
    umount_cgrp
    }
    load_tasks()
    {
    for (( i=1; i<=5; i++ ))
    do
    jj=$(eval echo "\$NR_TASKS$i")
    shares="1024"
    if [ $PRO_SHARES -eq 1 ]
    then
    eval shares=$(echo "$jj * 1024" | bc)
    fi
    echo $hares > $MOUNT/$i/cpu.shares
    for (( j=1; j<=$jj; j++ ))
    do
    echo "-1" > $MOUNT/$i/cpu.cfs_quota_us
    echo "500000" > $MOUNT/$i/cpu.cfs_period_us
    if [ $SUBGROUP -eq 1 ]
    then
    $LOAD &
    echo $! > $MOUNT/$i/$j/tasks
    echo "1024" > $MOUNT/$i/$j/cpu.shares
    if [ $BANDWIDTH -eq 1 ]
    then
    echo "500000" > $MOUNT/$i/$j/cpu.cfs_period_us
    echo "250000" > $MOUNT/$i/$j/cpu.cfs_quota_us
    fi
    else
    $LOAD &
    echo $! > $MOUNT/$i/tasks
    echo $shares > $MOUNT/$i/cpu.shares
    if [ $BANDWIDTH -eq 1 ]
    then
    echo "500000" > $MOUNT/$i/cpu.cfs_period_us
    echo "250000" > $MOUNT/$i/cpu.cfs_quota_us
    fi
    fi
    done
    done
    echo "Captuing idle cpu time with vmstat...."
    vmstat 2 100 &> vmstat_log &
    }
    pin_tasks()
    {
    cpu=0
    count=1
    for (( i=1; i<=5; i++ ))
    do
    if [ $SUBGROUP -eq 1 ]
    then
    jj=$(eval echo "\$NR_TASKS$i")
    for (( j=1; j<=$jj; j++ ))
    do
    if [ $count -gt 2 ]
    then
    cpu=$((cpu+1))
    count=1
    fi
    echo $cpu > $MOUNT/$i/$j/cpuset.cpus
    count=$((count+1))
    done
    else
    case $i in
    1)
    echo 0 > $MOUNT/$i/cpuset.cpus;;
    2)
    echo 1 > $MOUNT/$i/cpuset.cpus;;
    3)
    echo "2-3" > $MOUNT/$i/cpuset.cpus;;
    4)
    echo "4-6" > $MOUNT/$i/cpuset.cpus;;
    5)
    echo "7-15" > $MOUNT/$i/cpuset.cpus;;
    esac
    fi
    done
    }
    print_results()
    {
    eval gtot=$(cat sched_log|grep -i while|sed 's/R//g'|awk '{gtot+=$7};END{printf "%f", gtot}')
    for (( i=1; i<=5; i++ ))
    do
    eval temp=$(cat sched_log_$i|sed 's/R//g'| awk '{gtot+=$7};END{printf "%f",gtot}')
    eval tavg=$(echo "scale=4;(($temp / $gtot) * $1)/100 " | bc)
    eval avg=$(echo "scale=4;($temp / $gtot) * 100" | bc)
    eval pretty_tavg=$( echo "scale=4; $tavg * 100"| bc) # F0r pretty format
    echo "Bandwidth of Group $i = $avg i.e = $pretty_tavg% of non-Idle CPU time $1%"
    if [ $SUBGROUP -eq 1 ]
    then
    jj=$(eval echo "\$NR_TASKS$i")
    for (( j=1; j<=$jj; j++ ))
    do
    eval tmp=$(cat sched_log_$i-$j|sed 's/R//g'| awk '{gtot+=$7};END{printf "%f",gtot}')
    eval stavg=$(echo "scale=4;($tmp / $temp) * 100" | bc)
    eval pretty_stavg=$(echo "scale=4;(($tmp / $temp) * $tavg) * 100" | bc)
    echo -n "|"
    echo -e "...... subgroup $i/$j\t= $stavg\ti.e = $pretty_stavg% of $pretty_tavg% Groups non-Idle CPU time"
    done
    fi
    echo " "
    echo " "
    done
    }
    capture_results()
    {
    cat /proc/sched_debug > sched_log
    pkill -9 vmstat -c
    avg=$(cat vmstat_log |grep -iv "system"|grep -iv "swpd"|awk ' { if ( NR != 1) {id+=$15 }}END{print (id/NR)}')
    rem=$(echo "scale=2; 100 - $avg" |bc)
    echo "Average CPU Idle percentage $avg%"
    echo "Bandwidth shared with remaining non-Idle $rem%"
    for (( i=1; i<=5; i++ ))
    do
    cat sched_log |grep -i while1|grep -i " \/$i" > sched_log_$i
    if [ $SUBGROUP -eq 1 ]
    then
    jj=$(eval echo "\$NR_TASKS$i")
    for (( j=1; j<=$jj; j++ ))
    do
    cat sched_log |grep -i while1|grep -i " \/$i\/$j" > sched_log_$i-$j
    done
    fi
    done
    print_results $rem
    }
    create_hierarchy
    pin_tasks
    load_tasks
    sleep 60
    capture_results
    cleanup
    exit

    Thanks,
    Kamalesh.


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