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diff --git a/Documentation/cgroup-v1/hugetlb.rst b/Documentation/cgroup-v1/hugetlb.rst new file mode 100644 index 000000000000..a3902aa253a9 --- /dev/null +++ b/Documentation/cgroup-v1/hugetlb.rst @@ -0,0 +1,50 @@ +================== +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 usage for "hugepagesize" hugetlb + hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB limit + +For a system supporting three hugepage sizes (64k, 32M and 1G), the control +files include:: + + hugetlb.1GB.limit_in_bytes + hugetlb.1GB.max_usage_in_bytes + hugetlb.1GB.usage_in_bytes + hugetlb.1GB.failcnt + hugetlb.64KB.limit_in_bytes + hugetlb.64KB.max_usage_in_bytes + hugetlb.64KB.usage_in_bytes + hugetlb.64KB.failcnt + hugetlb.32MB.limit_in_bytes + hugetlb.32MB.max_usage_in_bytes + hugetlb.32MB.usage_in_bytes + hugetlb.32MB.failcnt |