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hugetlb/cgroup: add HugeTLB controller documentation 

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aneesh Kumar K.V 2012-07-31 16:42:30 -07:00 committed by Linus Torvalds
parent 8e6ac7fab3
commit 585e27ea6d
1 changed files with 45 additions and 0 deletions
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Documentation/cgroups/hugetlb.txt Normal file
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HugeTLB Controller
-------------------
The HugeTLB controller allows to limit the HugeTLB usage per control group and
enforces the controller limit during page fault. Since HugeTLB doesn't
support page reclaim, enforcing the limit at page fault time implies that,
the application will get SIGBUS signal if it tries to access HugeTLB pages
beyond its limit. This requires the application to know beforehand how much
HugeTLB pages it would require for its use.
HugeTLB controller can be created by first mounting the cgroup filesystem.
# mount -t cgroup -o hugetlb none /sys/fs/cgroup
With the above step, the initial or the parent HugeTLB group becomes
visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in
the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup.
New groups can be created under the parent group /sys/fs/cgroup.
# cd /sys/fs/cgroup
# mkdir g1
# echo $$ > g1/tasks
The above steps create a new group g1 and move the current shell
process (bash) into it.
Brief summary of control files
hugetlb.<hugepagesize>.limit_in_bytes # set/show limit of "hugepagesize" hugetlb usage
hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded
hugetlb.<hugepagesize>.usage_in_bytes # show current res_counter usage for "hugepagesize" hugetlb
hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB limit
For a system supporting two hugepage size (16M and 16G) the control
files include:
hugetlb.16GB.limit_in_bytes
hugetlb.16GB.max_usage_in_bytes
hugetlb.16GB.usage_in_bytes
hugetlb.16GB.failcnt
hugetlb.16MB.limit_in_bytes
hugetlb.16MB.max_usage_in_bytes
hugetlb.16MB.usage_in_bytes
hugetlb.16MB.failcnt