mi-malloc  1.0
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)
 Type of deferred free functions. More...
 
typedef void() mi_output_fun(const char *msg)
 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 (mi_output_fun *out)
 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 (mi_output_fun *out)
 Print out heap statistics for this thread. More...
 
void mi_register_deferred_free (mi_deferred_free_fun *deferred_free)
 Register a deferred free function. More...
 
void mi_register_output (mi_output_fun *out) mi_attr_noexcept
 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 (size_t pages, double max_secs, size_t *pages_reserved)
 Reserve pages of huge OS pages (1GiB) but stops after at most max_secs 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)

Type of deferred free functions.

Parameters
forceIf true all outstanding items should be freed.
heartbeatA monotonically increasing count.
See also
mi_register_deferred_free

◆ mi_output_fun

typedef void() mi_output_fun(const char *msg)

Type of output functions.

Parameters
msgMessage to output.
See also
mi_register_output()

Function Documentation

◆ mi_collect()

void mi_collect ( bool  force)

Eagerly free memory.

Parameters
forceIf 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
sizeThe 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
pThe 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
sizeThe 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)

Register a deferred free function.

Parameters
deferred_freeAddress of a deferred free-ing function or NULL to unregister.

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)

Register an output function.

Parameters
outThe output function, use NULL to output to stdout.

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

◆ mi_reserve_huge_os_pages()

int mi_reserve_huge_os_pages ( size_t  pages,
double  max_secs,
size_t *  pages_reserved 
)

Reserve pages of huge OS pages (1GiB) but stops after at most max_secs seconds.

Parameters
pagesThe number of 1GiB pages to reserve.
max_secsMaximum number of seconds to try reserving.
pages_reservedIf not NULL, it is set to the actual number of pages that were reserved.
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 max_secs are expired if it estimates it will take more than 1.5 times max_secs. 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()

void mi_stats_print ( mi_output_fun out)

Print the main statistics.

Parameters
outOutput function. Use NULL for outputting to stderr.

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()

void mi_thread_stats_print ( mi_output_fun out)

Print out heap statistics for this thread.

Parameters
outOutput function. Use NULL for outputting to stderr.

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
pPointer 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
sizeThe 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!