Guardian Native C Library Calls Reference Manual (G06.29+, H06.08+, J06.03+)

heap_min_block_size(3) Guardian Native C Library Calls Reference Manual

NAME

heap_min_block_size - Speciﬁes the minimum block size to attempt to use when allocating

from the heap

LIBRARY

G-series native Guardian processes: $SYSTEM.SYSnn.ZCRTLSRL

G-series native OSS processes: /G/system/sysnn/zcrtlsrl

H-series and J-series native Guardian processes: $SYSTEM.ZDLLnnn.ZCRTLDLL

32-bit H-series and J-series OSS processes: /G/system/zdllnnn/zcrtldll

64-bit H-series and J-series OSS processes: /G/system/zdllnnn/ycrtldll

SYNOPSIS

#include <stdlib.h>

void heap_min_block_size (

long min_block_size);

PARAMETERS

min_block_size Speciﬁes the number of bytes to be allocated.

DESCRIPTION

The heap_min_block_size() function speciﬁes to the run-time library the minimum block size to

attempt to use when an allocation is made from the heap. If a larger block size is required than

the minimum speciﬁed block size, the minimum value is ignored.

If a program makes many calls to the the memory-management functions calloc(), free(), mal-

loc(), and realloc() to allocate and deallocate small blocks of memory and these calls are inter-

spersed with many calls to allocate large blocks of memory, the heap can become very frag-

mented with many small, almost useless free blocks. This memory conﬁguration can have a

detrimental effect on the run-time efﬁciency of the routines that traverse the "free-list" searching

for a block of memory of the proper size to allocate. By judiciously choosing a value for

heap_min_block_size(), you can tune the performance of your program.

RELATED INFORMATION

Functions: heap_check(3), heap_check_always(3).

STANDARDS CONFORMANCE

The heap_min_block_size() function is an HP extension to the XPG4 Version 2 speciﬁcation.

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