C Interface to Scalable Allocator¶
[memory_allocation.scalable_alloc_c_interface]
Low-level interface for scalable memory allocation.
// Defined in header <tbb/scalable_allocator.h>
extern "C" {
// Scalable analogs of C memory allocator
void* scalable_malloc( size_t size );
void scalable_free( void* ptr );
void* scalable_calloc( size_t nobj, size_t size );
void* scalable_realloc( void* ptr, size_t size );
// Analog of _msize/malloc_size/malloc_usable_size.
size_t scalable_msize( void* ptr );
// Scalable analog of posix_memalign
int scalable_posix_memalign( void** memptr, size_t alignment, size_t size );
// Aligned allocation
void* scalable_aligned_malloc( size_t size, size_t alignment);
void scalable_aligned_free( void* ptr );
void* scalable_aligned_realloc( void* ptr, size_t size, size_t alignment );
// Return values for scalable_allocation_* functions
typedef enum {
TBBMALLOC_OK,
TBBMALLOC_INVALID_PARAM,
TBBMALLOC_UNSUPPORTED,
TBBMALLOC_NO_MEMORY,
TBBMALLOC_NO_EFFECT
} ScalableAllocationResult;
typedef enum {
// To turn on/off the use of huge memory pages
TBBMALLOC_USE_HUGE_PAGES,
// To set a threshold for the allocator memory usage.
// Exceeding it will forcefully clean internal memory buffers
TBBMALLOC_SET_SOFT_HEAP_LIMIT,
// Lower bound for the size (Bytes), that is interpreted as huge
// and not released during regular cleanup operations
TBBMALLOC_SET_HUGE_SIZE_THRESHOLD
} AllocationModeParam;
// Set allocator-specific allocation modes.
int scalable_allocation_mode(int param, intptr_t value);
typedef enum {
// Clean internal allocator buffers for all threads.
TBBMALLOC_CLEAN_ALL_BUFFERS,
// Clean internal allocator buffer for current thread only.
TBBMALLOC_CLEAN_THREAD_BUFFERS
} ScalableAllocationCmd;
// Call allocator-specific commands.
int scalable_allocation_command(int cmd, void *param);
}
These functions provide a C-level interface to the scalable allocator.
With the exception of scalable_allocation_mode
and scalable_allocation_command
, each routine scalable_x
behaves analogously to the library function x
. The routines form the two families shown in
the table below, “C Interface to Scalable Allocator”.
Storage allocated by a scalable_x
function in one family must be freed or
resized by the scalable_x
function in the same family, not by a C standard library function. Likewise, storage allocated by a C
standard library function should not be freed or resized by a scalable_x
function.
Allocation Routine |
Deallocation Routine |
Analogous Library |
---|---|---|
scalable_malloc |
scalable_free |
C standard library |
scalable_calloc |
||
scalable_realloc |
||
scalable_posix_memalign |
POSIX* |
|
scalable_aligned_malloc |
scalable_aligned_free |
Microsoft* C run-time library |
scalable_aligned_realloc |
The following functions do not allocate or free memory but allow obtaining useful information or influencing behavior of the memory allocator.
-
size_t
scalable_msize
(void *ptr)¶ Returns: The usable size of the memory block pointed to by ptr if it was allocated by the scalable allocator. Returns zero if ptr does not point to such a block.
-
int
scalable_allocation_mode
(int mode, intptr_t value)¶ Use this function to adjust behavior of the scalable memory allocator.
Returns: TBBMALLOC_OK if the operation succeeded, TBBMALLOC_INVALID_PARAM if
mode
is not one of the described below, or ifvalue
is not valid for the given mode. Other return values are possible, as described below.
scalable_allocation_mode Parameters: Parameter, Description
-
TBBMALLOC_USE_HUGE_PAGES
¶ scalable_allocation_mode(TBBMALLOC_USE_HUGE_PAGES, 1)
tells the allocator to use huge pages if enabled by the operating system.scalable_allocation_mode(TBBMALLOC_USE_HUGE_PAGES, 0)
disables it. SettingTBB_MALLOC_USE_HUGE_PAGES
environment variable to 1 has the same effect asscalable_allocation_mode(TBBMALLOC_USE_HUGE_PAGES, 1)
. The mode set withscalable_allocation_mode()
takes priority over the environment variable.May return:
TBBMALLOC_NO_EFFECT
if huge pages are not supported on the platform.For now, this allocation mode is only supported for Linux* OS. It works with both explicitly configured and transparent huge pages. For information about enabling and configuring huge pages, refer to OS documentation or ask your system administrator.
-
TBBMALLOC_SET_SOFT_HEAP_LIMIT
¶ scalable_allocation_mode(TBBMALLOC_SET_SOFT_HEAP_LIMIT, size)
sets a threshold ofsize
bytes on the amount of memory the allocator takes from OS. Exceeding the threshold urges the allocator to release memory from its internal buffers; however it does not prevent from requesting more memory if needed.
-
TBBMALLOC_SET_HUGE_SIZE_THRESHOLD
¶ scalable_allocation_mode(TBBMALLOC_SET_HUGE_SIZE_THRESHOLD, size)
sets a lower bound threshold (with no upper limit) ofsize
bytes. Any object bigger than this threshold becomes huge and does not participate in internal periodic cleanup logic. However, it does not affect the logic of theTBBMALLOC_SET_SOFT_HEAP_LIMIT
mode as well as theTBBMALLOC_CLEAN_ALL_BUFFERS
operation.Setting
TBB_MALLOC_SET_HUGE_SIZE_THRESHOLD
environment variable to the size value has the same effect, but is limited to theLONG_MAX
value. The mode set withscalable_allocation_mode
takes priority over the environment variable.
-
int
scalable_allocation_command
(int cmd, void *reserved)¶ This function may be used to command the scalable memory allocator to perform an action specified by the first parameter. The second parameter is reserved and must be set to 0.
Returns:
TBBMALLOC_OK
if the operation succeeded,TBBMALLOC_INVALID_PARAM
ifcmd
is not one of the described below, or ifreserved
is not equal to 0.
scalable_allocation_command Parameters: Parameter, Description
-
TBBMALLOC_CLEAN_ALL_BUFFERS
¶ scalable_allocation_command(TBBMALLOC_CLEAN_ALL_BUFFERS, 0)
cleans internal memory buffers of the allocator, and possibly reduces memory footprint. It may result in increased time for subsequent memory allocation requests. The command is not designed for frequent use, and careful evaluation of the performance impact is recommended.May return:
TBBMALLOC_NO_EFFECT
if no buffers were released.Note
It is not guaranteed that the call will release all unused memory.
-
TBBMALLOC_CLEAN_THREAD_BUFFERS
¶ scalable_allocation_command(TBBMALLOC_CLEAN_THREAD_BUFFERS, 0)
cleans internal memory buffers, but only for the calling thread.May return:
TBBMALLOC_NO_EFFECT
if no buffers were released.