Documentation/cgroup-v1/hugetlb.txt

   1 HugeTLB Controller
   2 -------------------
   3
   4 The HugeTLB controller allows to limit the HugeTLB usage per control group and
   5 enforces the controller limit during page fault. Since HugeTLB doesn't
   6 support page reclaim, enforcing the limit at page fault time implies that,
   7 the application will get SIGBUS signal if it tries to access HugeTLB pages
   8 beyond its limit. This requires the application to know beforehand how much
   9 HugeTLB pages it would require for its use.
  10
  11 HugeTLB controller can be created by first mounting the cgroup filesystem.
  12
  13 # mount -t cgroup -o hugetlb none /sys/fs/cgroup
  14
  15 With the above step, the initial or the parent HugeTLB group becomes
  16 visible at /sys/fs/cgroup. At bootup, this group includes all the tasks in
  17 the system. /sys/fs/cgroup/tasks lists the tasks in this cgroup.
  18
  19 New groups can be created under the parent group /sys/fs/cgroup.
  20
  21 # cd /sys/fs/cgroup
  22 # mkdir g1
  23 # echo $$ > g1/tasks
  24
  25 The above steps create a new group g1 and move the current shell
  26 process (bash) into it.
  27
  28 Brief summary of control files
  29
  30  hugetlb.<hugepagesize>.limit_in_bytes     # set/show limit of "hugepagesize" hugetlb usage
  31  hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb  usage recorded
  32  hugetlb.<hugepagesize>.usage_in_bytes     # show current usage for "hugepagesize" hugetlb
  33  hugetlb.<hugepagesize>.failcnt            # show the number of allocation failure due to HugeTLB limit
  34
  35 For a system supporting three hugepage sizes (64k, 32M and 1G), the control
  36 files include:
  37
  38 hugetlb.1GB.limit_in_bytes
  39 hugetlb.1GB.max_usage_in_bytes
  40 hugetlb.1GB.usage_in_bytes
  41 hugetlb.1GB.failcnt
  42 hugetlb.64KB.limit_in_bytes
  43 hugetlb.64KB.max_usage_in_bytes
  44 hugetlb.64KB.usage_in_bytes
  45 hugetlb.64KB.failcnt
  46 hugetlb.32MB.limit_in_bytes
  47 hugetlb.32MB.max_usage_in_bytes
  48 hugetlb.32MB.usage_in_bytes
  49 hugetlb.32MB.failcnt