linux-toradex.git/block/blk-cgroup.c, branch v2.6.38.8

blk-cgroup: Allow creation of hierarchical cgroups

2010-11-15T18:37:36+00:00

o Allow hierarchical cgroup creation for blkio controller

o Currently we disallow it as both the io controller policies (throttling
  as well as proportion bandwidth) do not support hierarhical accounting
  and control. But the flip side is that blkio controller can not be used with
  libvirt as libvirt creates a cgroup hierarchy deeper than 1 level.

  //libvirt/qemu/

o So this patch will allow creation of cgroup hierarhcy but at the backend
  everything will be treated as flat. So if somebody created a an hierarchy
  like as follows.

			root
			/  \
		     test1 test2
			|
		     test3

  CFQ and throttling will practically treat all groups at same level.

				pivot
			     /  |   \  \
			root  test1 test2  test3

o Once we have actual support for hierarchical accounting and control
  then we can introduce another cgroup tunable file "blkio.use_hierarchy"
  which will be 0 by default but if user wants to enforce hierarhical
  control then it can be set to 1. This way there should not be any
  ABI problems down the line.

o The only not so pretty part is introduction of extra file "use_hierarchy"
  down the line. Kame-san had mentioned that hierarhical accounting is
  expensive in memory controller hence they keep it off by default. I
  suspect same will be the case for IO controller also as for each IO
  completion we shall have to account IO through hierarchy up to the root.
  if yes, then it probably is not a very bad idea to introduce this extra
  file so that it will be used only when somebody needs it and some people
  might enable hierarchy only in part of the hierarchy.

o This is how basically memory controller also uses "use_hierarhcy" and
  they also allowed creation of hierarchies when actual backend support
  was not available.

Signed-off-by: Vivek Goyal 
Acked-by: Balbir Singh 
Reviewed-by: Gui Jianfeng 
Reviewed-by: Ciju Rajan K 
Tested-by: Ciju Rajan K 
Signed-off-by: Jens Axboe

Merge branch 'for-2.6.37/core' of git://git.kernel.dk/linux-2.6-block

2010-10-23T00:00:32+00:00

* 'for-2.6.37/core' of git://git.kernel.dk/linux-2.6-block: (39 commits)
  cfq-iosched: Fix a gcc 4.5 warning and put some comments
  block: Turn bvec_k{un,}map_irq() into static inline functions
  block: fix accounting bug on cross partition merges
  block: Make the integrity mapped property a bio flag
  block: Fix double free in blk_integrity_unregister
  block: Ensure physical block size is unsigned int
  blkio-throttle: Fix possible multiplication overflow in iops calculations
  blkio-throttle: limit max iops value to UINT_MAX
  blkio-throttle: There is no need to convert jiffies to milli seconds
  blkio-throttle: Fix link failure failure on i386
  blkio: Recalculate the throttled bio dispatch time upon throttle limit change
  blkio: Add root group to td->tg_list
  blkio: deletion of a cgroup was causes oops
  blkio: Do not export throttle files if CONFIG_BLK_DEV_THROTTLING=n
  block: set the bounce_pfn to the actual DMA limit rather than to max memory
  block: revert bad fix for memory hotplug causing bounces
  Fix compile error in blk-exec.c for !CONFIG_DETECT_HUNG_TASK
  block: set the bounce_pfn to the actual DMA limit rather than to max memory
  block: Prevent hang_check firing during long I/O
  cfq: improve fsync performance for small files
  ...

Fix up trivial conflicts due to __rcu sparse annotation in include/linux/genhd.h

blkio-throttle: limit max iops value to UINT_MAX

2010-10-01T19:16:41+00:00

- Limit max iops value to UINT_MAX and return error to user if value is more
  than that instead of accepting bigger values and truncating implicitly.

Signed-off-by: Jens Axboe

blkio: Recalculate the throttled bio dispatch time upon throttle limit change

2010-10-01T12:49:49+00:00

o Currently any cgroup throttle limit changes are processed asynchronousy and
  the change does not take affect till a new bio is dispatched from same group.

o It might happen that a user sets a redicuously low limit on throttling.
  Say 1 bytes per second on reads. In such cases simple operations like mount
  a disk can wait for a very long time.

o Once bio is throttled, there is no easy way to come out of that wait even if
  user increases the read limit later.

o This patch fixes it. Now if a user changes the cgroup limits, we recalculate
  the bio dispatch time according to new limits.

o Can't take queueu lock under blkcg_lock, hence after the change I wake
  up the dispatch thread again which recalculates the time. So there are some
  variables being synchronized across two threads without lock and I had to
  make use of barriers. Hoping I have used barriers correctly. Any review of
  memory barrier code especially will help.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blkio: deletion of a cgroup was causes oops

2010-10-01T12:49:44+00:00

o Now a cgroup list of blkg elements can contain blkg from multiple policies.
  Before sending an unlink event, make sure blkg belongs to they policy. If
  policy does not own the blkg, do not send update for this blkg.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blkio: Do not export throttle files if CONFIG_BLK_DEV_THROTTLING=n

2010-10-01T12:49:41+00:00

Currently throttling related files were visible even if user had disabled
throttling using config options. It was switching off background throttling
of bio but not the cgroup files. This patch fixes it.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blk-cgroup: cgroup changes for IOPS limit support

2010-09-16T06:42:58+00:00

o cgroup changes for IOPS throttling rules.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blk-cgroup: Introduce cgroup changes for throttling policy

2010-09-16T06:42:12+00:00

o cgroup chagnes for throttle policy.

o Introduces READ and WRITE bytes per second throttling rules.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blk-cgroup: Prepare the base for supporting more than one IO control policies

2010-09-16T06:42:04+00:00

o This patch prepares the base for introducing new IO control policies.
  Currently all the code is written knowing there is only one policy
  and that is proportional bandwidth. Creating infrastructure for newer
  policies to come in.

o Also there were many functions which were generated using macro. It was
  very confusing. Got rid of those.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe

blk-cgroup: Kill the header printed at the start of blkio.weight_device file

2010-09-16T06:40:42+00:00

o Kill extra "dev weight" header which is printed when somebody reads
  blkio.weight_device file. This really seems to be out of convention. No other
  blkio files are printing any header at the start of file. I think it is ok
  to just print values and how to interpret values should be part of
  documentation.

Signed-off-by: Vivek Goyal 
Signed-off-by: Jens Axboe