[PATCHSET v2] blk-throttle: implement proper hierarchy support

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

Changes since the last take[L] are

* Unnecessary throtl_schedule_delayed_work() call dropped from 0007.

* throtl_log() implement in 0021 forgot to print space after blkg
  path.  Fixed.

* 0030-blk-throttle-add-throtl_qnode-for-dispatch-fairness.patch added
  to address dispatch fairness.

* 0031-blk-throttle-Account-for-child-group-s-start-time-in.patch
  added to address unwarranted penalty of nested limit enforcement due
  to staggered delays of slice start times at multiple levels.

The original patchset description follows.

blk-throttle is the last controller with broken hierarchy support
making blkcg the last one tagged with .broken_hierarchy.  This
patchset implements hierarchy support for blk-throttle.  The semantics
is pretty simple - limits on an intermediate node applies to the whole
subtree and the statistics remain local.

As this changes the meaning of the knobs in an incompatible manner -
e.g. configuring limits on root cgroup now means setting the limit for
the whole system - the hierarchy mode is enabled by "sane_behavior"
cgroup mount flag.  If the flag is not specified, the original broken
flat hierarchy behavior is retained.

While this patchset contains many patches, the implementation is
pretty straight-forward.  throtl_grp's form a tree anchored at
throtl_data and bios climb the tree as they get dispatched at each
level.  The bios which reach the top of the tree - throl_data - are
issued.  The scheduling algorithm remains unchanged at each level and
blk-throttle should behave the same for flat hierarchy after the
changes.  The same algorithm is repeated until bios clear all limits
to the top of the tree.

This patchset contains the following 33 patches.

 0001-blkcg-fix-error-return-path-in-blkg_create.patch
 0002-blkcg-move-blkg_for_each_descendant_pre-to-block-blk.patch
 0003-blkcg-implement-blkg_for_each_descendant_post.patch
 0004-blkcg-invoke-blkcg_policy-pd_init-after-parent-is-li.patch
 0005-blkcg-move-bulk-of-blkcg_gq-release-operations-to-th.patch
 0006-blk-throttle-remove-spurious-throtl_enqueue_tg-call-.patch
 0007-blk-throttle-removed-deferred-config-application-mec.patch
 0008-blk-throttle-collapse-throtl_dispatch-into-the-work-.patch
 0009-blk-throttle-relocate-throtl_schedule_delayed_work.patch
 0010-blk-throttle-remove-pointless-throtl_nr_queued-optim.patch
 0011-blk-throttle-rename-throtl_rb_root-to-throtl_service.patch
 0012-blk-throttle-simplify-throtl_grp-flag-handling.patch
 0013-blk-throttle-add-backlink-pointer-from-throtl_grp-to.patch
 0014-blk-throttle-pass-around-throtl_service_queue-instea.patch
 0015-blk-throttle-reorganize-throtl_service_queue-passed-.patch
 0016-blk-throttle-add-throtl_grp-service_queue.patch
 0017-blk-throttle-move-bio_lists-and-friends-to-throtl_se.patch
 0018-blk-throttle-dispatch-to-throtl_data-service_queue.b.patch
 0019-blk-throttle-generalize-update_disptime-optimization.patch
 0020-blk-throttle-add-throtl_service_queue-parent_sq.patch
 0021-blk-throttle-implement-sq_to_tg-sq_to_td-and-throtl_.patch
 0022-blk-throttle-set-REQ_THROTTLED-from-throtl_charge_bi.patch
 0023-blk-throttle-separate-out-throtl_service_queue-pendi.patch
 0024-blk-throttle-implement-dispatch-looping.patch
 0025-blk-throttle-dispatch-from-throtl_pending_timer_fn.patch
 0026-blk-throttle-make-blk_throtl_drain-ready-for-hierarc.patch
 0027-blk-throttle-make-blk_throtl_bio-ready-for-hierarchy.patch
 0028-blk-throttle-make-tg_dispatch_one_bio-ready-for-hier.patch
 0029-blk-throttle-make-throtl_pending_timer_fn-ready-for-.patch
 0030-blk-throttle-add-throtl_qnode-for-dispatch-fairness.patch
 0031-blk-throttle-Account-for-child-group-s-start-time-in.patch
 0032-blk-throttle-implement-throtl_grp-has_rules.patch
 0033-blk-throttle-implement-proper-hierarchy-support.patch

0001-0005 prepare blkcg so that hierarchy operations are easier.

0006-0016 reorganize code piece-by-piece so that hierarchy support can
be added.  These don't change behaviors.

0017-0025 prepare for hierarchy support.  Moves fields which are used
in hierarchy to throtl_service_queue and define parent-child
relationship.

0026-0032 make queueing, dispatching and configuration changes
propagate through the hierarchy.

0033 implemenats hierarchy support.

As we're in the middle of a merge window, this patchset is currently
based on cgroup/for-3.10.  Once 3.10-rc1 drops, I'll rebase the tree
and send pull request to Jens so that it can be routed with other
block changes.  The patches are also available on the following git
branch.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-throtl-hierarchy

diffstat follows.  Thanks.

 block/blk-cgroup.c     |  105 +---
 block/blk-cgroup.h     |   38 +
 block/blk-throttle.c   | 1064 ++++++++++++++++++++++++++++++++++---------------
 include/linux/cgroup.h |    2 
 4 files changed, 822 insertions(+), 387 deletions(-)

--
tejun

[L] http://thread.gmane.org/gmane.linux.kernel.containers/25845