cgroup: enable refcnting for root csses

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Currently, css_get(), css_tryget() and css_tryget_online() are noops
for root csses as an optimization; however, we're planning to use css
refcnts to track of cgroup lifetime too and root cgroups also need to
be reference counted.  Since css has been converted to percpu_refcnt,
the overhead of refcnting is miniscule and this optimization isn't too
meaningful anymore.  Furthermore, controllers which optimize the root
cgroup often never even invoke these functions in their hot paths.

This patch enables refcnting for root csses too.  This makes CSS_ROOT
flag unused and removes it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

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This commit is contained in:

Tejun Heo 2014-05-14 09:15:02 -04:00

parent 25e15d8350

commit 9395a45004

2 changed files with 5 additions and 11 deletions

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10

include/linux/cgroup.h

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6

kernel/cgroup.c

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