Messages in this thread | | | From | Paul Turner <> | Date | Tue, 7 Jun 2011 20:09:09 -0700 | Subject | Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinned |
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[ Sorry for the delayed response, I was out on vacation for the second half of May until last week -- I've now caught up on email and am preparing the next posting ]
Thanks for the test-case Kamalesh -- my immediate suspicion is quota return may not be fine-grained enough (although the numbers provided are large enough it's possible there's also just a bug).
I have some tools from my own testing I can use to pull this apart, let me run your work-load and get back to you.
On Tue, Jun 7, 2011 at 8:45 AM, Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> wrote: > 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. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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