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Date: Thu, 5 Nov 2009 05:06:12 +0530 From: Balbir Singh <balbir@...ux.vnet.ibm.com> To: Vivek Goyal <vgoyal@...hat.com> Cc: linux-kernel@...r.kernel.org, jens.axboe@...cle.com, nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com, ryov@...inux.co.jp, fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp, guijianfeng@...fujitsu.com, jmoyer@...hat.com, righi.andrea@...il.com, m-ikeda@...jp.nec.com, akpm@...ux-foundation.org, riel@...hat.com, kamezawa.hiroyu@...fujitsu.com Subject: Re: [PATCH 01/20] blkio: Documentation * Vivek Goyal <vgoyal@...hat.com> [2009-11-04 12:52:44]: > On Wed, Nov 04, 2009 at 10:51:00PM +0530, Balbir Singh wrote: > > * Vivek Goyal <vgoyal@...hat.com> [2009-11-03 18:43:38]: > > > > > Signed-off-by: Vivek Goyal <vgoyal@...hat.com> > > > --- > > > Documentation/cgroups/blkio-controller.txt | 106 ++++++++++++++++++++++++++++ > > > 1 files changed, 106 insertions(+), 0 deletions(-) > > > create mode 100644 Documentation/cgroups/blkio-controller.txt > > > > > > diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt > > > new file mode 100644 > > > index 0000000..dc8fb1a > > > --- /dev/null > > > +++ b/Documentation/cgroups/blkio-controller.txt > > > @@ -0,0 +1,106 @@ > > > + Block IO Controller > > > + =================== > > > +Overview > > > +======== > > > +cgroup subsys "blkio" implements the block io controller. There seems to be > > > +a need of various kind of IO control policies (like proportional BW, max BW) > > > +both at leaf nodes as well as at intermediate nodes in storage hierarchy. Plan > > > +is to use same cgroup based management interface for blkio controller and > > > +based on user options switch IO policies in the background. > > > + > > > +In the first phase, this patchset implements proportional weight time based > > > +division of disk policy. It is implemented in CFQ. Hence this policy takes > > > +effect only on leaf nodes when CFQ is being used. > > > + > > > +HOWTO > > > +===== > > > +You can do a very simple testing of running two dd threads in two different > > > +cgroups. Here is what you can do. > > > + > > > +- Enable group scheduling in CFQ > > > + CONFIG_CFQ_GROUP_IOSCHED=y > > > + > > > +- Compile and boot into kernel and mount IO controller (blkio). > > > + > > > + mount -t cgroup -o blkio none /cgroup > > > + > > > +- Create two cgroups > > > + mkdir -p /cgroup/test1/ /cgroup/test2 > > > + > > > +- Set weights of group test1 and test2 > > > + echo 1000 > /cgroup/test1/blkio.weight > > > + echo 500 > /cgroup/test2/blkio.weight > > > + > > > +- Create two same size files (say 512MB each) on same disk (file1, file2) and > > > + launch two dd threads in different cgroup to read those files. > > > + > > > + sync > > > + echo 3 > /proc/sys/vm/drop_caches > > > + > > > + dd if=/mnt/sdb/zerofile1 of=/dev/null & > > > + echo $! > /cgroup/test1/tasks > > > + cat /cgroup/test1/tasks > > > + > > > + dd if=/mnt/sdb/zerofile2 of=/dev/null & > > > + echo $! > /cgroup/test2/tasks > > > + cat /cgroup/test2/tasks > > > + > > > +- At macro level, first dd should finish first. To get more precise data, keep > > > + on looking at (with the help of script), at blkio.disk_time and > > > + blkio.disk_sectors files of both test1 and test2 groups. This will tell how > > > + much disk time (in milli seconds), each group got and how many secotors each > > > + group dispatched to the disk. We provide fairness in terms of disk time, so > > > + ideally io.disk_time of cgroups should be in proportion to the weight. > > > + > > > +Various user visible config options > > > +=================================== > > > +CONFIG_CFQ_GROUP_IOSCHED > > > + - Enables group scheduling in CFQ. Currently only 1 level of group > > > + creation is allowed. > > > + > > > +CONFIG_DEBUG_CFQ_IOSCHED > > > + - Enables some debugging messages in blktrace. Also creates extra > > > + cgroup file blkio.dequeue. > > > + > > > +Config options selected automatically > > > +===================================== > > > +These config options are not user visible and are selected/deselected > > > +automatically based on IO scheduler configuration. > > > + > > > +CONFIG_BLK_CGROUP > > > + - Block IO controller. Selected by CONFIG_CFQ_GROUP_IOSCHED. > > > + > > > +CONFIG_DEBUG_BLK_CGROUP > > > + - Debug help. Selected by CONFIG_DEBUG_CFQ_IOSCHED. > > > + > > > +Details of cgroup files > > > +======================= > > > +- blkio.ioprio_class > > > + - Specifies class of the cgroup (RT, BE, IDLE). This is default io > > > + class of the group on all the devices. > > > + > > > + 1 = RT; 2 = BE, 3 = IDLE > > > + > > > +- blkio.weight > > > + - Specifies per cgroup weight. > > > + > > > + Currently allowed range of weights is from 100 to 1000. > > > + > > > +- blkio.time > > > + - disk time allocated to cgroup per device in milliseconds. First > > > + two fields specify the major and minor number of the device and > > > + third field specifies the disk time allocated to group in > > > + milliseconds. > > > + > > > +- blkio.sectors > > > + - number of sectors transferred to/from disk by the group. First > > > + two fields specify the major and minor number of the device and > > > + third field specifies the number of sectors transferred by the > > > + group to/from the device. > > > + > > > +- blkio.dequeue > > > + - Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This > > > + gives the statistics about how many a times a group was dequeued > > > + from service tree of the device. First two fields specify the major > > > + and minor number of the device and third field specifies the number > > > + of times a group was dequeued from a particular device. > > > > Hi, Vivek, > > > > Are the parameters inter-related? What if you have conflicts w.r.t. > > time, sectors, etc? > > What kind of conflicts? > > time, sectors, and dequeue are read only files. They are mainly for > monitoring purposes. CFQ provides fairness in terms of disk time, so one > can monitor whether time share received by a group is fair or not. > > "sectors" just gives additional data of how many sectors were transferred. > It it not a necessary file. I just exported it to get some sense of both > time and amount IO done by cgroup. > > So I am not sure what kind of conflicts you are referring to. > OK, so they are read only statistics? I seemed to parse the document differently -- Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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