| 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 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 |
