On Thu, May 07, 2009 at 11:36:42AM -0400, Vivek Goyal wrote: > On Thu, May 07, 2009 at 10:45:01AM -0400, Vivek Goyal wrote: > > On Thu, May 07, 2009 at 10:11:26AM -0400, Vivek Goyal wrote: > > > > [..] > > > [root@chilli io-throttle-tests]# ./andrea-test-script.sh > > > RT: 223+1 records in > > > RT: 223+1 records out > > > RT: 234179072 bytes (234 MB) copied, 0.988448 s, 237 MB/s > > > BE: 223+1 records in > > > BE: 223+1 records out > > > BE: 234179072 bytes (234 MB) copied, 1.93885 s, 121 MB/s > > > > > > So I am still seeing the issue with differnt kind of disks also. At this point > > > of time I am really not sure why I am seeing such results. > > > > Hold on. I think I found the culprit here. I was thinking that what is > > the difference between two setups and realized that with vanilla kernels > > I had done "make defconfig" and with io-throttle kernels I had used an > > old config of my and did "make oldconfig". So basically config files > > were differnt. > > > > I now used the same config file and issues seems to have gone away. I > > will look into why an old config file can force such kind of issues. > > > > Hmm.., my old config had "AS" as default scheduler that's why I was seeing > the strange issue of RT task finishing after BE. My apologies for that. I > somehow assumed that CFQ is default scheduler in my config. > > So I have re-run the test to see if we are still seeing the issue of > loosing priority and class with-in cgroup. And we still do.. > > 2.6.30-rc4 with io-throttle patches > =================================== > Test1 > ===== > - Two readers, one BE prio 0 and other BE prio 7 in a cgroup limited with > 8MB/s BW. > > 234179072 bytes (234 MB) copied, 55.8448 s, 4.2 MB/s > prio 0 task finished > 234179072 bytes (234 MB) copied, 55.8878 s, 4.2 MB/s > > Test2 > ===== > - Two readers, one RT prio 0 and other BE prio 7 in a cgroup limited with > 8MB/s BW. > > 234179072 bytes (234 MB) copied, 55.8876 s, 4.2 MB/s > 234179072 bytes (234 MB) copied, 55.8984 s, 4.2 MB/s > RT task finished > > Test3 > ===== > - Reader Starvation > - I created a cgroup with BW limit of 64MB/s. First I just run the reader > alone and then I run reader along with 4 writers 4 times. > > Reader alone > 234179072 bytes (234 MB) copied, 3.71796 s, 63.0 MB/s > > Reader with 4 writers > --------------------- > First run > 234179072 bytes (234 MB) copied, 30.394 s, 7.7 MB/s > > Second run > 234179072 bytes (234 MB) copied, 26.9607 s, 8.7 MB/s > > Third run > 234179072 bytes (234 MB) copied, 37.3515 s, 6.3 MB/s > > Fourth run > 234179072 bytes (234 MB) copied, 36.817 s, 6.4 MB/s > > Note that out of 64MB/s limit of this cgroup, reader does not get even > 1/5 of the BW. In normal systems, readers are advantaged and reader gets > its job done much faster even in presence of multiple writers. > > Vanilla 2.6.30-rc4 > ================== > > Test3 > ===== > Reader alone > 234179072 bytes (234 MB) copied, 2.52195 s, 92.9 MB/s > > Reader with 4 writers > --------------------- > First run > 234179072 bytes (234 MB) copied, 4.39929 s, 53.2 MB/s > > Second run > 234179072 bytes (234 MB) copied, 4.55929 s, 51.4 MB/s > > Third run > 234179072 bytes (234 MB) copied, 4.79855 s, 48.8 MB/s > > Fourth run > 234179072 bytes (234 MB) copied, 4.5069 s, 52.0 MB/s > > Notice, that without any writers we seem to be having BW of 92MB/s and > more than 50% of that BW is still assigned to reader in presence of > writers. Compare this with io-throttle cgroup of 64MB/s where reader > struggles to get 10-15% of BW. > > So any 2nd level control will break the notion and assumptions of > underlying IO scheduler. We should probably do control at IO scheduler > level to make sure we don't run into such issues while getting > hierarchical fair share for groups. > Forgot to attached my reader-writer script last time. Here it is. *************************************************************** #!/bin/bash mount /dev/sdb1 /mnt/sdb mount -t cgroup -o blockio blockio /cgroup/iot/ mkdir -p /cgroup/iot/test1 /cgroup/iot/test2 # Set bw limit of 64 MB/ps on sdb echo "/dev/sdb:$((64 * 1024 * 1024)):0:0" > /cgroup/iot/test1/blockio.bandwidth-max sync echo 3 > /proc/sys/vm/drop_caches echo $$ > /cgroup/iot/test1/tasks ionice -c 2 -n 7 dd if=/dev/zero of=/mnt/sdb/testzerofile1 bs=4K count=524288 & echo $! ionice -c 2 -n 7 dd if=/dev/zero of=/mnt/sdb/testzerofile2 bs=4K count=524288 & echo $! ionice -c 2 -n 7 dd if=/dev/zero of=/mnt/sdb/testzerofile3 bs=4K count=524288 & echo $! ionice -c 2 -n 7 dd if=/dev/zero of=/mnt/sdb/testzerofile4 bs=4K count=524288 & echo $! sleep 5 echo "Launching reader" ionice -c 2 -n 0 dd if=/mnt/sdb/zerofile2 of=/dev/zero & pid2=$! echo $pid2 wait $pid2 echo "Reader Finished" killall dd ********************************************************************** Thanks Vivek -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
