Messages in this thread |  | | Date | Thu, 15 Sep 2011 23:25:38 +0530 | | From | Kamalesh Babulal <> | | Subject | Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinnede |
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* Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> [2011-09-14 00:05:02]:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> [2011-09-13 20:30:46]: > > > On Tue, 2011-09-13 at 23:58 +0530, Srivatsa Vaddagiri wrote: > > > * Peter Zijlstra <a.p.zijlstra@chello.nl> [2011-09-13 20:19:55]: > > > > > > > On Tue, 2011-09-13 at 23:24 +0530, Srivatsa Vaddagiri wrote: > > > > > We saw considerably high migration count on latest tip compared to > > > > > previous kernels. Kamalesh, can you please post the migration count > > > > > data? > > > > > > > > Hrmm, yes this looks horrid.. even without cgroup crap, something's funny. > > > > > > Yes ..we could visualize that very much in top o/p .. A task's cpu would keep > > > changing *every* screen refresh (refreshed every 0.5 sec that too!). > > > > > > We didn't see that with older kernels ..Kamalesh is planning to do a > > > git bisect and see which commit lead to this "mad" hopping .. > > > > Awesome, thanks! Btw, what is 'older'? 3.0? > > We went back all the way upto 2.6.32! I think 2.6.38 and 2.6.39 were > pretty stable ..I don't have the migration count data with me readily. I > will let Kamalesh post that info soon.
Test Setup : ----------- Machine is 2 socket Quad Core Intel (x5570) box. The lb.sh script was run in a loop to execute 5 times after the box was bought up with the kernel.
lb.sh script spawns 2x number of CPU hogs, where x is number of CPUs on the system. The script collects the se.nr_migration before/after 60 seconds sleep and subtracts the after_se.nr_migration - before_se.nr_migrations for all the spawned hogs. ----------------+-------+-------+-------+-------+-------+ Kernel | Run 1 | Run 2 | Run 3 | Run 4 | Run 5 | ----------------+-------+-------+-------+-------+-------+ 2.6.33 | 9604 | 101 | 66 | 2543 | 3488 | ----------------+-------+-------+-------+-------+-------+ 2.6.34 | 28469 | 1514 | 1602 | 185 | 139 | ----------------+-------+-------+-------+-------+-------+ 2.6.35 | 1052 | 12 | 4 | 11 | 6 | ----------------+-------+-------+-------+-------+-------+ 2.6.36 | 1253 | 53 | 78 | 76 | 50 | ----------------+-------+-------+-------+-------+-------+ 2.6.37 | 262 | 36 | 48 | 61 | 43 | ----------------+-------+-------+-------+-------+-------+ 2.6.38 | 1551 | 48 | 62 | 47 | 50 | ----------------+-------+-------+-------+-------+-------+ 2.6.39 | 3784 | 457 | 722 | 3209 | 1037 | ----------------+-------+-------+-------+-------+-------+ 3.0 | 933 | 608 | 658 | 1424 | 1415 | ----------------+-------+-------+-------+-------+-------+ 3.1.0-rc4-tip | | | | | | (e467f18f945) | 1672 | 1643 | 1316 | 1577 | 61 | ----------------+-------+-------+-------+-------+-------+
lb.sh ------ #!/bin/bash
rm -rf test* rm -rf t*
ITERATIONS=60 # No of Iterations to capture the details NUM_CPUS=$(cat /proc/cpuinfo |grep -i proces|wc -l)
NUM_HOGS=$((NUM_CPUS * 2)) # No of hogs threads to invoke
echo "System has $NUM_CPUS cpus..... Spawing $NUM_HOGS cpu hogs ... for $ITERATIONS seconds.." if [ ! -e while1.c ] then cat >> while1.c << EOF int main (int argc, char **argv) { while(1); return (0); } EOF fi
for i in $(seq 1 $NUM_HOGS) do gcc -o while$i while1.c if [ $? -ne 0 ] then echo "Looks like gcc is not present ... aborting" exit fi done
for i in $(seq 1 $NUM_HOGS) do ./while$i & pids[$i]=$! pids_old[$i]=`cat /proc/$!/sched |grep -i nr_migr|grep -iv cold|cut -d ":" -f2|sed 's/ //g'` done
sleep $ITERATIONS
j=1 old_nr_migrations=0 new_nr_migrations=0 echo -e " \t New \t Old" for i in $(seq 1 $NUM_HOGS) do a=`echo ${pids[i]}` new=`cat /proc/$a/sched |grep -i nr_migr|grep -iv cold|cut -d ":" -f2|sed 's/ //g'` old=`echo ${pids_old[i]}` old_nr_migrations=$((old_nr_migrations + old)) c=$(($new - $old)) new_nr_migrations=$((new_nr_migrations + c)) echo -e "while$i\t[$new]\t[$old]\t" done echo "*******************************************" echo -e " $new_nr_migrations\t$old_nr_migrations" echo "*******************************************" pkill -9 while
exit
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