Extended Functions

Extended functionality. More...

Macros
#define	MI_SMALL_SIZE_MAX
	Maximum size allowed for small allocations in mi_malloc_small and mi_zalloc_small (usually 128*sizeof(void*) (= 1KB on 64-bit systems)) More...

Typedefs
typedef void()	mi_deferred_free_fun(bool force, unsigned long long heartbeat, void *arg)
	Type of deferred free functions. More...
typedef void()	mi_output_fun(const char *msg, void *arg)
	Type of output functions. More...

Functions
void *	mi_malloc_small (size_t size)
	Allocate a small object. More...
void *	mi_zalloc_small (size_t size)
	Allocate a zero initialized small object. More...
size_t	mi_usable_size (void *p)
	Return the available bytes in a memory block. More...
size_t	mi_good_size (size_t size)
	Return the used allocation size. More...
void	mi_collect (bool force)
	Eagerly free memory. More...
void	mi_stats_print (void *out)
	Print the main statistics. More...
void	mi_stats_print (mi_output_fun *out, void *arg)
	Print the main statistics. More...
void	mi_stats_reset (void)
	Reset statistics. More...
void	mi_stats_merge (void)
	Merge thread local statistics with the main statistics and reset. More...
void	mi_thread_init (void)
	Initialize mimalloc on a thread. More...
void	mi_thread_done (void)
	Uninitialize mimalloc on a thread. More...
void	mi_thread_stats_print_out (mi_output_fun *out, void *arg)
	Print out heap statistics for this thread. More...
void	mi_register_deferred_free (mi_deferred_free_fun *deferred_free, void *arg)
	Register a deferred free function. More...
void	mi_register_output (mi_output_fun *out, void *arg)
	Register an output function. More...
bool	mi_is_in_heap_region (const void *p)
	Is a pointer part of our heap? More...
int	mi_reserve_huge_os_pages_interleave (size_t pages, size_t numa_nodes, size_t timeout_msecs)
	Reserve pages of huge OS pages (1GiB) evenly divided over numa_nodes nodes, but stops after at most timeout_msecs seconds. More...
int	mi_reserve_huge_os_pages_at (size_t pages, int numa_node, size_t timeout_msecs)
	Reserve pages of huge OS pages (1GiB) at a specific numa_node, but stops after at most timeout_msecs seconds. More...
bool	mi_is_redirected ()
	Is the C runtime malloc API redirected? More...

Detailed Description

Extended functionality.

Macro Definition Documentation

MI_SMALL_SIZE_MAX

#define MI_SMALL_SIZE_MAX

Maximum size allowed for small allocations in mi_malloc_small and mi_zalloc_small (usually 128*sizeof(void*) (= 1KB on 64-bit systems))

Typedef Documentation

mi_deferred_free_fun

typedef void() mi_deferred_free_fun(bool force, unsigned long long heartbeat, void *arg)

Type of deferred free functions.

Parameters

force	If true all outstanding items should be freed.
heartbeat	A monotonically increasing count.
arg	Argument that was passed at registration to hold extra state.

See also

mi_register_deferred_free

mi_output_fun

typedef void() mi_output_fun(const char *msg, void *arg)

Type of output functions.

Parameters

msg	Message to output.
arg	Argument that was passed at registration to hold extra state.

See also

mi_register_output()

Function Documentation

mi_collect()

void mi_collect

(

bool

force

)

Eagerly free memory.

Parameters

force

If true, aggressively return memory to the OS (can be expensive!)

Regular code should not have to call this function. It can be beneficial in very narrow circumstances; in particular, when a long running thread allocates a lot of blocks that are freed by other threads it may improve resource usage by calling this every once in a while.

mi_good_size()

size_t mi_good_size

(

size_t

size

)

Return the used allocation size.

Parameters

size	The minimal required size in bytes.

Returns

the size n that will be allocated, where n >= size.

Generally, mi_usable_size(mi_malloc(size)) == mi_good_size(size). This can be used to reduce internal wasted space when allocating buffers for example.

See also

mi_usable_size()

mi_is_in_heap_region()

bool mi_is_in_heap_region

(

const void *

p

)

Is a pointer part of our heap?

Parameters

p	The pointer to check.

Returns

true if this is a pointer into our heap. This function is relatively fast.

mi_is_redirected()

bool mi_is_redirected

(

)

Is the C runtime malloc API redirected?

Returns

true if all malloc API calls are redirected to mimalloc.

Currenty only used on Windows.

mi_malloc_small()

void* mi_malloc_small

(

size_t

size

)

Allocate a small object.

Parameters

size	The size in bytes, can be at most MI_SMALL_SIZE_MAX.

Returns

a pointer to newly allocated memory of at least size bytes, or NULL if out of memory. This function is meant for use in run-time systems for best performance and does not check if size was indeed small – use with care!

mi_register_deferred_free()

void mi_register_deferred_free	(	mi_deferred_free_fun *	deferred_free,
		void *	arg
	)

Register a deferred free function.

Parameters

deferred_free	Address of a deferred free-ing function or NULL to unregister.
arg	Argument that will be passed on to the deferred free function.

Some runtime systems use deferred free-ing, for example when using reference counting to limit the worst case free time. Such systems can register (re-entrant) deferred free function to free more memory on demand. When the force parameter is true all possible memory should be freed. The per-thread heartbeat parameter is monotonically increasing and guaranteed to be deterministic if the program allocates deterministically. The deferred_free function is guaranteed to be called deterministically after some number of allocations (regardless of freeing or available free memory). At most one deferred_free function can be active.

mi_register_output()

void mi_register_output	(	mi_output_fun *	out,
		void *	arg
	)

Register an output function.

Parameters

out	The output function, use NULL to output to stderr.
arg	Argument that will be passed on to the output function.

The out function is called to output any information from mimalloc, like verbose or warning messages.

mi_reserve_huge_os_pages_at()

int mi_reserve_huge_os_pages_at	(	size_t	pages,
		int	numa_node,
		size_t	timeout_msecs
	)

Reserve pages of huge OS pages (1GiB) at a specific numa_node, but stops after at most timeout_msecs seconds.

Parameters

pages	The number of 1GiB pages to reserve.
numa_node	The NUMA node where the memory is reserved (start at 0).
timeout_msecs	Maximum number of milli-seconds to try reserving, or 0 for no timeout.

Returns

0 if successfull, ENOMEM if running out of memory, or ETIMEDOUT if timed out.

The reserved memory is used by mimalloc to satisfy allocations. May quit before timeout_msecs are expired if it estimates it will take more than 1.5 times timeout_msecs. The time limit is needed because on some operating systems it can take a long time to reserve contiguous memory if the physical memory is fragmented.

mi_reserve_huge_os_pages_interleave()

int mi_reserve_huge_os_pages_interleave	(	size_t	pages,
		size_t	numa_nodes,
		size_t	timeout_msecs
	)

Reserve pages of huge OS pages (1GiB) evenly divided over numa_nodes nodes, but stops after at most timeout_msecs seconds.

Parameters

pages	The number of 1GiB pages to reserve.
numa_nodes	The number of nodes do evenly divide the pages over, or 0 for using the actual number of NUMA nodes.
timeout_msecs	Maximum number of milli-seconds to try reserving, or 0 for no timeout.

Returns

0 if successfull, ENOMEM if running out of memory, or ETIMEDOUT if timed out.

The reserved memory is used by mimalloc to satisfy allocations. May quit before timeout_msecs are expired if it estimates it will take more than 1.5 times timeout_msecs. The time limit is needed because on some operating systems it can take a long time to reserve contiguous memory if the physical memory is fragmented.

mi_stats_merge()

void mi_stats_merge

(

void

)

Merge thread local statistics with the main statistics and reset.

mi_stats_print() [1/2]

void mi_stats_print

(

void *

out

)

Print the main statistics.

Parameters

out	Ignored, outputs to the registered output function or stderr by default.

Most detailed when using a debug build.

mi_stats_print() [2/2]

void mi_stats_print	(	mi_output_fun *	out,
		void *	arg
	)

Print the main statistics.

Parameters

out	An output function or NULL for the default.
arg	Optional argument passed to out (if not NULL)

Most detailed when using a debug build.

mi_stats_reset()

void mi_stats_reset

(

void

)

Reset statistics.

mi_thread_done()

void mi_thread_done

(

void

)

Uninitialize mimalloc on a thread.

Should not be used as on most systems (pthreads, windows) this is done automatically. Ensures that any memory that is not freed yet (but will be freed by other threads in the future) is properly handled.

mi_thread_init()

void mi_thread_init

(

void

)

Initialize mimalloc on a thread.

Should not be used as on most systems (pthreads, windows) this is done automatically.

mi_thread_stats_print_out()

void mi_thread_stats_print_out	(	mi_output_fun *	out,
		void *	arg
	)

Print out heap statistics for this thread.

Parameters

out	An output function or NULL for the default.
arg	Optional argument passed to out (if not NULL)

Most detailed when using a debug build.

mi_usable_size()

size_t mi_usable_size

(

void *

p

)

Return the available bytes in a memory block.

Parameters

p	Pointer to previously allocated memory (or NULL)

Returns

Returns the available bytes in the memory block, or 0 if p was NULL.

The returned size can be used to call mi_expand successfully. The returned size is always at least equal to the allocated size of p, and, in the current design, should be less than 16.7% more.

See also

_msize (Windows)

malloc_usable_size (Linux)

mi_good_size()

mi_zalloc_small()

void* mi_zalloc_small

(

size_t

size

)

Allocate a zero initialized small object.

Parameters

size	The size in bytes, can be at most MI_SMALL_SIZE_MAX.

Returns

a pointer to newly allocated zero-initialized memory of at least size bytes, or NULL if out of memory. This function is meant for use in run-time systems for best performance and does not check if size was indeed small – use with care!