# Configuring the Memory Allocator

The oneTBB memory allocator provides the following API functions and environment variables to configure its behavior:

- the `scalable_allocation_command` function instructs the allocator to perform a certain action, such as cleaning up its internal memory buffers.

- the `scalable_allocation_mode` function allows an application to set certain parameters for the memory allocator, such as an option to map memory in huge pages or define a recommended heap size. These settings take effect until modified by another call to `scalable_allocation_mode`.

Some of the memory allocator parameters can also be set via system environment variables. It can be useful to adjust the behavior without modifying application source code, to ensure that a setting takes effect as early as possible, or to avoid explicit dependency on the oneTBB allocator binaries. The following environment variables are recognized:

- `TBB_MALLOC_USE_HUGE_PAGES` controls usage of huge pages for memory mapping.

- `TBB_MALLOC_SET_HUGE_OBJECT_THRESHOLD` defines the lower bound for the size (bytes), that is interpreted as huge and not released during regular cleanup operations.

These variables only take effect at the time the memory manager is initialized; later environment changes are ignored. A call to `scalable_allocation_mode` overrides the effect of the corresponding environment variable.