Messages in this thread | | | Date | Wed, 4 Nov 2009 22:51:00 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH 01/20] blkio: Documentation |
| |
* Vivek Goyal <vgoyal@redhat.com> [2009-11-03 18:43:38]:
> Signed-off-by: Vivek Goyal <vgoyal@redhat.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?
-- Balbir
| |