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 | 40 ++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index dff8d5985f0f..cf3092eb239a 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -218,6 +218,46 @@ 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_THP_POLICY_DEFAULT_HUGE + This will set the MMF2_THP_VMA_DEFAULT_HUGE process flag which + changes the default of new VMAs to be VM_HUGEPAGE. The call + also modifies all existing VMAs that are not VM_NOHUGEPAGE + to be VM_HUGEPAGE. The policy is inherited during fork+exec. + + PR_THP_POLICY_DEFAULT_NOHUGE + This will set the MMF2_THP_VMA_DEFAULT_NOHUGE process flag which + changes the default of new VMAs to be VM_NOHUGEPAGE. The call + also modifies all existing VMAs that are not VM_HUGEPAGE + to be VM_NOHUGEPAGE. The policy is inherited during fork+exec. + + PR_THP_POLICY_DEFAULT_SYSTEM + This will clear both MMF2_THP_VMA_DEFAULT_HUGE and + MMF2_THP_VMA_DEFAULT_NOHUGE process flags. + +PR_SET_THP_POLICY + This will return the current THP policy of the process, i.e. + PR_THP_POLICY_DEFAULT_HUGE, PR_THP_POLICY_DEFAULT_NOHUGE or + PR_THP_POLICY_DEFAULT_SYSTEM. + Khugepaged controls ------------------- -- 2.47.1
