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mi-malloc: Extended Functions

Internal 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))
 

Typedefs

typedef void mi_deferred_free_fun(bool force, unsigned long long heartbeat, void *arg)
 Type of deferred free functions.
 
typedef void mi_output_fun(const char *msg, void *arg)
 Type of output functions.
 
typedef void mi_error_fun(int err, void *arg)
 Type of error callback functions.
 
int mi_version (void)
 Return the mimalloc version.
 
void mi_collect (bool force)
 Eagerly free memory.
 
void mi_thread_set_in_threadpool (void)
 v3: Communicate that a thread is in a threadpool.
 
bool mi_is_redirected ()
 Is the C runtime malloc API redirected?
 
void mi_thread_init (void)
 Initialize mimalloc on a thread.
 
void mi_thread_done (void)
 Uninitialize mimalloc on a thread.
 
void mi_register_deferred_free (mi_deferred_free_fun *deferred_free, void *arg)
 Register a deferred free function.
 
void mi_register_output (mi_output_fun *out, void *arg)
 Register an output function.
 
void mi_register_error (mi_error_fun *errfun, void *arg)
 Register an error callback function.
 
void * mi_malloc_small (size_t size)
 Allocate a small object.
 
void * mi_zalloc_small (size_t size)
 Allocate a zero initialized small object.
 

Internal functionality.

◆ 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))

◆ mi_deferred_free_fun

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

Type of deferred free functions.

Parameters
forceIf true all outstanding items should be freed.
heartbeatA monotonically increasing count.
argArgument that was passed at registration to hold extra state.
See also
mi_register_deferred_free

◆ mi_error_fun

typedef void mi_error_fun(int err, void *arg)

Type of error callback functions.

Parameters
errError code (see mi_register_error() for a complete list).
argArgument that was passed at registration to hold extra state.
See also
mi_register_error()

◆ mi_output_fun

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

Type of output functions.

Parameters
msgMessage to output.
argArgument that was passed at registration to hold extra state.
See also
mi_register_output()

◆ 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_is_redirected()

bool mi_is_redirected ( )

Is the C runtime malloc API redirected?

Returns
true if all malloc API calls are redirected to mimalloc.

Currently 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,
void * arg )

Register a deferred free function.

Parameters
deferred_freeAddress of a deferred free-ing function or NULL to unregister.
argArgument 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_error()

void mi_register_error ( mi_error_fun * errfun,
void * arg )

Register an error callback function.

Parameters
errfunThe error function that is called on an error (use NULL for default)
argExtra argument that will be passed on to the error function.

The errfun function is called on an error in mimalloc after emitting an error message (through the output function). It as always legal to just return from the errfun function in which case allocation functions generally return NULL or ignore the condition. The default function only calls abort() when compiled in secure mode with an EFAULT error. The possible error codes are:

  • EAGAIN: Double free was detected (only in debug and secure mode).
  • EFAULT: Corrupted free list or meta-data was detected (only in debug and secure mode).
  • ENOMEM: Not enough memory available to satisfy the request.
  • EOVERFLOW: Too large a request, for example in mi_calloc(), the count and size parameters are too large.
  • EINVAL: Trying to free or re-allocate an invalid pointer.

◆ mi_register_output()

void mi_register_output ( mi_output_fun * out,
void * arg )

Register an output function.

Parameters
outThe output function, use NULL to output to stderr.
argArgument 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_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_set_in_threadpool()

void mi_thread_set_in_threadpool ( void )

v3: Communicate that a thread is in a threadpool.

This is done automatically for threads in the Windows threadpool, but if using a custom threadpool it is good to call this on worker threads. Internally, mimalloc uses different locality heuristics for worker threads to try to reduce non-local accesss.

◆ mi_version()

Return the mimalloc version.

Returns
The version. For v1,v2 the version is 100*major + 10*minor + patch (for example 227 for v2.2.7). For v3, it is 1000*major + 100*minor + path (for example, 3207 for v3.2.7).

◆ 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!