This includes the already existing PR_GET/SET_THP_DISABLE policy, as well as the newly introduced PR_GET/SET_THP_POLICY. Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx> --- Documentation/admin-guide/mm/transhuge.rst | 42 ++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index dff8d5985f0f..79983c20ae48 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -218,6 +218,48 @@ to "always" or "madvise"), and it'll be automatically shutdown when PMD-sized THP is disabled (when both the per-size anon control and the top-level control are "never") +process THP controls +-------------------- + +Transparent Hugepage behaviour of a process can be modified/obtained by +using the prctl system call. The following operations are supported: + +PR_SET_THP_DISABLE + This will set the MMF_DISABLE_THP process flag which will result + in no hugepages being faulted in or collapsed by khugepaged, + irrespective of global THP controls. + +PR_GET_THP_DISABLE + This will return the MMF_DISABLE_THP process flag, which will be + set if the process has previously been set with PR_SET_THP_DISABLE. + +PR_SET_THP_POLICY + This is used to change the behaviour of existing and future VMAs. + It has support for the following policies: + + PR_DEFAULT_MADV_HUGEPAGE + This will set VM_HUGEPAGE and clear VM_NOHUGEPAGE for the default + VMA flags. It will also iterate through every VMA in the process + and call hugepage_madvise on it, with MADV_HUGEPAGE policy. + This effectively allows setting MADV_HUGEPAGE on the entire process. + The policy is inherited during fork+exec. + + PR_DEFAULT_MADV_NOHUGEPAGE + This will set VM_NOHUGEPAGE and clear VM_HUGEPAGE for the default + VMA flags. It will also iterate through every VMA in the process + and call hugepage_madvise on it, with MADV_NOHUGEPAGE policy. + This effectively allows setting MADV_NOHUGEPAGE on the entire process. + The policy is inherited during fork+exec. + + PR_THP_POLICY_SYSTEM + This will reset (clear) both VM_HUGEPAGE and VM_NOHUGEPAGE process + for the default flags. + +PR_SET_THP_POLICY + This will return the current THP policy of the process, i.e. + PR_DEFAULT_MADV_HUGEPAGE, PR_DEFAULT_MADV_NOHUGEPAGE or + PR_THP_POLICY_SYSTEM. + Khugepaged controls ------------------- -- 2.47.1
