You can adjust some parameters for dynamic memory allocation with the
mallopt function. This function is the general SVID/XPG
interface, defined in malloc.h.
Preliminary: | MT-Unsafe init const:mallopt | AS-Unsafe init lock | AC-Unsafe init lock | See POSIX Safety Concepts.
mallopt, the param argument specifies the
parameter to be set, and value the new value to be set. Possible
choices for param, as defined in malloc.h, are:
The maximum number of chunks to allocate with
mmap. Setting this
to zero disables all use of
All chunks larger than this value are allocated outside the normal
heap, using the
mmap system call. This way it is guaranteed
that the memory for these chunks can be returned to the system on
free. Note that requests smaller than this threshold might still
be allocated via
If non-zero, memory blocks are filled with values depending on some
low order bits of this parameter when they are allocated (except when
calloc) and freed. This can be used to debug the
use of uninitialized or freed heap memory. Note that this option does not
guarantee that the freed block will have any specific values. It only
guarantees that the content the block had before it was freed will be
This parameter determines the amount of extra memory to obtain from the
system when a call to
sbrk is required. It also specifies the
number of bytes to retain when shrinking the heap by calling
with a negative argument. This provides the necessary hysteresis in
heap size such that excessive amounts of system calls can be avoided.
This is the minimum size (in bytes) of the top-most, releasable chunk
that will cause
sbrk to be called with a negative argument in
order to return memory to the system.