| 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 |