Parameters Used to Configure Transparent HugePages

The following table describes selected parameter settings that can be used when configuring Transparent HugePages (THP).

Table 3-1 Commonly Used THP Parameters

Parameter	File Location	Value Options
`enabled`	`/sys/kernel/mm/transparent_hugepage/enabled`	Sets THP and its mode, which is one of the following: `always (`default): THP is enabled in `system-wide` mode. In this setting, the kernel, whenever possible, assigns huge pages to processes using large contiguous virtual memory areas. `madvise`: THP is enabled in `per-process` mode. In this setting the kernel only assigns huge pages to application processes that explicitly request huge pages through the `madvise()`system call. `disabled`: THP is disabled.
`defrag`	`/sys/kernel/mm/transparent_hugepage/defrag`	Determines how aggressively an application can reclaim pages and defrag memory when THP is unavailable. The following list explains the available options: `always`: An application requesting THP stalls on allocation failure and directly reclaims pages and compact memory to obtain a THP immediately. `defer`: An application doesn't stall but continues using small pages. The application requests the kernel daemons `kswapd` and `kcompactd` to reclaim pages and compact memory so that THP is available later. `defer+madvise`: Regions using the `madvise(MADV_HUGEPAGE)` call stall on allocation failure and directly reclaim pages and compact memory to obtain a THP immediately However, all other regions request the kernel daemons `kswapd` and `kcompactd` to reclaim pages and compact memory so that THP is available later. `madvise` (default): Regions using the `madvise(MADV_HUGEPAGE)` call stall on allocation failure and directly reclaim pages and compact memory to obtain a THP immediately.