Hi Vivek, Here are some test results for normal reads and write for IO Controller V7 by fio. Tested with "fairness == 0". It seems performance gets better comparing with V6. Mode Normal read | Random read | Normal write | Random write | Direct read | Direct Write 2.6.31-rc1 71,613KiB/s 3,606KiB/s 66,250KiB/s 9,420KiB/s 51,535KiB/s 55,752KiB/s V7 70,540KiB/s 3,551KiB/s 64,548KiB/s 9,677KiB/s 53,530KiB/s 54,145KiB/s Performance -1.5% -1.5% -2.6% +2.7% +3.9% -2.9% Vivek Goyal wrote: > Hi All, > > Here is the V7 of the IO controller patches generated on top of 2.6.31-rc4. > > For ease of patching, a consolidated patch is available here. > > http://people.redhat.com/~vgoyal/io-controller/io-scheduler-based-io-controller-v7.patch > > Previous versions of the patches was posted here. > > (V1) http://lkml.org/lkml/2009/3/11/486 > (V2) http://lkml.org/lkml/2009/5/5/275 > (V3) http://lkml.org/lkml/2009/5/26/472 > (V4) http://lkml.org/lkml/2009/6/8/580 > (V5) http://lkml.org/lkml/2009/6/19/279 > (V6) http://lkml.org/lkml/2009/7/2/369 > > Changes from V6 > =============== > - Introduced the notion of group_idling where we idle for next request to > come from the same group before we expire it. It is along the lines of > cfq's slice_idle thing to provide fairness. Switching to group idling > now helps in the sense that we don't have to rely whether queue idling > was turned on or not by CFQ. It becomes too much of debugging pain with > different work loads and different kind of storage media. Introduction > of group_idle should help. > > - Moved some of the code like dynamic queue idling update, arming queue > idling timer, keeping track of average think time etc back to CFQ. With > group idling we don't need it now. Reduce the amount of change. > > - Enabled cfq's close cooperator functionality in groups. So far this worked > only in root group. Now it should work in non-root groups also. > > - Got rid of the patch where we calculated disk time based on average disk > rate in some circumstances. It was giving bad numbers in early queue > deletion cases. Also did not think that it was helping a lot. Remvoed it > for the time being. > > - Added an experimental patch to map sync requests using bio tracking info and > not task context. This is only for noop, deadline and AS. > > - Got rid of experimental patch of idling for async queues. Don't think it > was helping. > > - Got rid of wait_busy and wait_busy_done logic from queue. Instead > implemented it for groups. > > - Introduced oom_ioq to accomodate oom_cfqq change recently. > > - Broke-up elv_init_ioq() fn into smaller functions. It had 7 arguments and > looked complicated. > > - Fixed a bug in blk_queue_io_group_congested(). Thanks to Munehiro Ikeda. > > - Merged gui's patch to fix the cgroup file format issue. > > - Merged gui's patch to update per group congestion limit when > q->nr_group_requests is updated. > > - Fixed a bug where close cooperation will not work if we wait for all the > requests to finish from previous queue. > > - Fixed group deletion accouting where deletion from idle tree were also > appearing in the log. > > - Got rid of busy_rt_queues infrastructure. > > - Got rid of elv_ioq_request_dispatched(). An helper function just to > increment a variable. > > Limitations > =========== > > - This IO controller provides the bandwidth control at the IO scheduler > level (leaf node in stacked hiearchy of logical devices). So there can > be cases (depending on configuration) where application does not see > proportional BW division at higher logical level device. > > LWN has written an article about the issue here. > > http://lwn.net/Articles/332839/ > > How to solve the issue of fairness at higher level logical devices > ================================================================== > (Do we really need it? That's not where the contention for resources is.) > > Couple of suggestions have come forward. > > - Implement IO control at IO scheduler layer and then with the help of > some daemon, adjust the weight on underlying devices dynamiclly, depending > on what kind of BW gurantees are to be achieved at higher level logical > block devices. > > - Also implement a higher level IO controller along with IO scheduler > based controller and let user choose one depending on his needs. > > A higher level controller does not know about the assumptions/policies > of unerldying IO scheduler, hence it has the potential to break down > the IO scheduler's policy with-in cgroup. A lower level controller > can work with IO scheduler much more closely and efficiently. > > Other active IO controller developments > ======================================= > > IO throttling > ------------- > > This is a max bandwidth controller and not the proportional one. Secondly > it is a second level controller which can break the IO scheduler's > policy/assumtions with-in cgroup. > > dm-ioband > --------- > > This is a proportional bandwidth controller implemented as device mapper > driver. It is also a second level controller which can break the > IO scheduler's policy/assumptions with-in cgroup. > > TODO > ==== > - code cleanups, testing, bug fixing, optimizations, benchmarking etc... > > Testing > ======= > > I have been able to do some testing as follows. All my testing is with ext3 > file system with a SATA drive which supports queue depth of 31. > > Test1 (Isolation between two KVM virtual machines) > ================================================== > Created two KVM virtual machines. Partitioned a disk on host in two partitions > and gave one partition to each virtual machine. Put both the virtual machines > in two different cgroup of weight 1000 and 500 each. Virtual machines created > ext3 file system on the partitions exported from host and did buffered writes. > Host seems writes as synchronous and virtual machine with higher weight gets > double the disk time of virtual machine of lower weight. Used deadline > scheduler in this test case. > > Some more details about configuration are in documentation patch. > > Test2 (Fairness for synchronous reads) > ====================================== > - Two dd in two cgroups with cgrop weights 1000 and 500. Ran two "dd" in those > cgroups (With CFQ scheduler and /sys/block/<device>/queue/fairness = 1) > > Higher weight dd finishes first and at that point of time my script takes > care of reading cgroup files io.disk_time and io.disk_sectors for both the > groups and display the results. > > dd if=/mnt/$BLOCKDEV/zerofile1 of=/dev/null & > dd if=/mnt/$BLOCKDEV/zerofile2 of=/dev/null & > > 234179072 bytes (234 MB) copied, 3.9065 s, 59.9 MB/s > 234179072 bytes (234 MB) copied, 5.19232 s, 45.1 MB/s > > group1 time=8 16 2471 group1 sectors=8 16 457840 > group2 time=8 16 1220 group2 sectors=8 16 225736 > > First two fields in time and sectors statistics represent major and minor > number of the device. Third field represents disk time in milliseconds and > number of sectors transferred respectively. > > This patchset tries to provide fairness in terms of disk time received. group1 > got almost double of group2 disk time (At the time of first dd finish). These > time and sectors statistics can be read using io.disk_time and io.disk_sector > files in cgroup. More about it in documentation file. > > Test3 (Reader Vs Buffered Writes) > ================================ > Buffered writes can be problematic and can overwhelm readers, especially with > noop and deadline. IO controller can provide isolation between readers and > buffered (async) writers. > > First I ran the test without io controller to see the severity of the issue. > Ran a hostile writer and then after 10 seconds started a reader and then > monitored the completion time of reader. Reader reads a 256 MB file. Tested > this with noop scheduler. > > sample script > ------------ > sync > echo 3 > /proc/sys/vm/drop_caches > time dd if=/dev/zero of=/mnt/sdb/reader-writer-zerofile bs=4K count=2097152 > conv=fdatasync & > sleep 10 > time dd if=/mnt/sdb/256M-file of=/dev/null & > > Results > ------- > 8589934592 bytes (8.6 GB) copied, 106.045 s, 81.0 MB/s (Writer) > 268435456 bytes (268 MB) copied, 96.5237 s, 2.8 MB/s (Reader) > > Now it was time to test io controller whether it can provide isolation between > readers and writers with noop. I created two cgroups of weight 1000 each and > put reader in group1 and writer in group 2 and ran the test again. Upon > comletion of reader, my scripts read io.dis_time and io.disk_group cgroup > files to get an estimate how much disk time each group got and how many > sectors each group did IO for. > > For more accurate accounting of disk time for buffered writes with queuing > hardware I had to set /sys/block/<disk>/queue/iosched/fairness to "1". > > sample script > ------------- > echo $$ > /cgroup/bfqio/test2/tasks > dd if=/dev/zero of=/mnt/$BLOCKDEV/testzerofile bs=4K count=2097152 & > sleep 10 > echo noop > /sys/block/$BLOCKDEV/queue/scheduler > echo 1 > /sys/block/$BLOCKDEV/queue/iosched/fairness > echo $$ > /cgroup/bfqio/test1/tasks > dd if=/mnt/$BLOCKDEV/256M-file of=/dev/null & > wait $! > # Some code for reading cgroup files upon completion of reader. > ------------------------- > > Results > ======= > 268435456 bytes (268 MB) copied, 6.65819 s, 40.3 MB/s (Reader) > > group1 time=8 16 3063 group1 sectors=8 16 524808 > group2 time=8 16 3071 group2 sectors=8 16 441752 > > Note, reader finishes now much lesser time and both group1 and group2 > got almost 3 seconds of disk time. Hence io-controller provides isolation > from buffered writes. > > Test4 (AIO) > =========== > > AIO reads > ----------- > Set up two fio, AIO read jobs in two cgroup with weight 1000 and 500 > respectively. I am using cfq scheduler. Following are some lines from my test > script. > > --------------------------------------------------------------- > echo 1000 > /cgroup/bfqio/test1/io.weight > echo 500 > /cgroup/bfqio/test2/io.weight > > fio_args="--ioengine=libaio --rw=read --size=512M --direct=1" > echo 1 > /sys/block/$BLOCKDEV/queue/iosched/fairness > > echo $$ > /cgroup/bfqio/test1/tasks > fio $fio_args --name=test1 --directory=/mnt/$BLOCKDEV/fio1/ > --output=/mnt/$BLOCKDEV/fio1/test1.log > --exec_postrun="../read-and-display-group-stats.sh $maj_dev $minor_dev" & > > echo $$ > /cgroup/bfqio/test2/tasks > fio $fio_args --name=test2 --directory=/mnt/$BLOCKDEV/fio2/ > --output=/mnt/$BLOCKDEV/fio2/test2.log & > ---------------------------------------------------------------- > > test1 and test2 are two groups with weight 1000 and 500 respectively. > "read-and-display-group-stats.sh" is one small script which reads the > test1 and test2 cgroup files to determine how much disk time each group > got till first fio job finished. > > Results > ------ > test1 statistics: time=8 16 22403 sectors=8 16 1049640 > test2 statistics: time=8 16 11400 sectors=8 16 552864 > > Above shows that by the time first fio (higher weight), finished, group > test1 got 22403 ms of disk time and group test2 got 11400 ms of disk time. > similarly the statistics for number of sectors transferred are also shown. > > Note that disk time given to group test1 is almost double of group2 disk > time. > > AIO writes > ---------- > Set up two fio, AIO direct write jobs in two cgroup with weight 1000 and 500 > respectively. I am using cfq scheduler. Following are some lines from my test > script. > > ------------------------------------------------ > echo 1000 > /cgroup/bfqio/test1/io.weight > echo 500 > /cgroup/bfqio/test2/io.weight > fio_args="--ioengine=libaio --rw=write --size=512M --direct=1" > > echo 1 > /sys/block/$BLOCKDEV/queue/iosched/fairness > > echo $$ > /cgroup/bfqio/test1/tasks > fio $fio_args --name=test1 --directory=/mnt/$BLOCKDEV/fio1/ > --output=/mnt/$BLOCKDEV/fio1/test1.log > --exec_postrun="../read-and-display-group-stats.sh $maj_dev $minor_dev" & > > echo $$ > /cgroup/bfqio/test2/tasks > fio $fio_args --name=test2 --directory=/mnt/$BLOCKDEV/fio2/ > --output=/mnt/$BLOCKDEV/fio2/test2.log & > ------------------------------------------------- > > test1 and test2 are two groups with weight 1000 and 500 respectively. > "read-and-display-group-stats.sh" is one small script which reads the > test1 and test2 cgroup files to determine how much disk time each group > got till first fio job finished. > > Following are the results. > > test1 statistics: time=8 16 29085 sectors=8 16 1049656 > test2 statistics: time=8 16 14652 sectors=8 16 516728 > > Above shows that by the time first fio (higher weight), finished, group > test1 got 28085 ms of disk time and group test2 got 14652 ms of disk time. > similarly the statistics for number of sectors transferred are also shown. > > Note that disk time given to group test1 is almost double of group2 disk > time. > > Test5 (Fairness for async writes, Buffered Write Vs Buffered Write) > =================================================================== > Fairness for async writes is tricky and biggest reason is that async writes > are cached in higher layers (page cahe) as well as possibly in file system > layer also (btrfs, xfs etc), and are dispatched to lower layers not necessarily > in proportional manner. > > For example, consider two dd threads reading /dev/zero as input file and doing > writes of huge files. Very soon we will cross vm_dirty_ratio and dd thread will > be forced to write out some pages to disk before more pages can be dirtied. But > not necessarily dirty pages of same thread are picked. It can very well pick > the inode of lesser priority dd thread and do some writeout. So effectively > higher weight dd is doing writeouts of lower weight dd pages and we don't see > service differentation. > > IOW, the core problem with async write fairness is that higher weight thread > does not throw enought IO traffic at IO controller to keep the queue > continuously backlogged. In my testing, there are many .2 to .8 second > intervals where higher weight queue is empty and in that duration lower weight > queue get lots of job done giving the impression that there was no service > differentiation. > > In summary, from IO controller point of view async writes support is there. > Because page cache has not been designed in such a manner that higher > prio/weight writer can do more write out as compared to lower prio/weight > writer, gettting service differentiation is hard and it is visible in some > cases and not visible in some cases. > > Do we really care that much for fairness among two writer cgroups? One can > choose to do direct writes or sync writes if fairness for writes really > matters for him. > > Following is the only case where it is hard to ensure fairness between cgroups. > > - Buffered writes Vs Buffered Writes. > > So to test async writes I created two partitions on a disk and created ext3 > file systems on both the partitions. Also created two cgroups and generated > lots of write traffic in two cgroups (50 fio threads) and watched the disk > time statistics in respective cgroups at the interval of 2 seconds. Thanks to > ryo tsuruta for the test case. > > ***************************************************************** > sync > echo 3 > /proc/sys/vm/drop_caches > > fio_args="--size=64m --rw=write --numjobs=50 --group_reporting" > > echo $$ > /cgroup/bfqio/test1/tasks > fio $fio_args --name=test1 --directory=/mnt/sdd1/fio/ --output=/mnt/sdd1/fio/test1.log & > > echo $$ > /cgroup/bfqio/test2/tasks > fio $fio_args --name=test2 --directory=/mnt/sdd2/fio/ --output=/mnt/sdd2/fio/test2.log & > *********************************************************************** > > And watched the disk time and sector statistics for the both the cgroups > every 2 seconds using a script. How is snippet from output. > > test1 statistics: time=8 48 1315 sectors=8 48 55776 dq=8 48 1 > test2 statistics: time=8 48 633 sectors=8 48 14720 dq=8 48 2 > > test1 statistics: time=8 48 5586 sectors=8 48 339064 dq=8 48 2 > test2 statistics: time=8 48 2985 sectors=8 48 146656 dq=8 48 3 > > test1 statistics: time=8 48 9935 sectors=8 48 628728 dq=8 48 3 > test2 statistics: time=8 48 5265 sectors=8 48 278688 dq=8 48 4 > > test1 statistics: time=8 48 14156 sectors=8 48 932488 dq=8 48 6 > test2 statistics: time=8 48 7646 sectors=8 48 412704 dq=8 48 7 > > test1 statistics: time=8 48 18141 sectors=8 48 1231488 dq=8 48 10 > test2 statistics: time=8 48 9820 sectors=8 48 548400 dq=8 48 8 > > test1 statistics: time=8 48 21953 sectors=8 48 1485632 dq=8 48 13 > test2 statistics: time=8 48 12394 sectors=8 48 698288 dq=8 48 10 > > test1 statistics: time=8 48 25167 sectors=8 48 1705264 dq=8 48 13 > test2 statistics: time=8 48 14042 sectors=8 48 817808 dq=8 48 10 > > First two fields in time and sectors statistics represent major and minor > number of the device. Third field represents disk time in milliseconds and > number of sectors transferred respectively. > > So disk time consumed by group1 is almost double of group2 in this case. > > Your feedback is welcome. > > Thanks > Vivek > > > -- Regards Gui Jianfeng -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
