init_heap Kernel Service

Purpose

Initializes a new heap to be used with kernel memory management services.

Syntax

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/xmalloc.h>
#include <sys/malloc.h>

heapaddr_t init_heap ( area, size, heapp) caddr_t area; int size; heapaddr_t *heapp;

Parameters

Item	Description
area	Specifies the virtual memory address used to define the starting memory area for the heap. This address must be page-aligned.
size	Specifies the size of the heap in bytes. This value must be an integral number of system pages.
heapp	Points to the external heap descriptor. This must have a null value. The base kernel uses this field is used to specify special heap characteristics that are unavailable to kernel extensions.

Description

The init_heap kernel service is most commonly used by a kernel process to initialize and manage an area of virtual memory as a private heap. Once this service creates a private heap, the returned heapaddr_t value can be used with the xmalloc or xmfree service to allocate or deallocate memory from the private heap. Heaps can be created within other heaps, a kernel process private region, or even on a stack.

Few kernel extensions ever require the init_heap service because the exported global kernel_heap and pinned_heap are normally used for memory allocation within the kernel. However, kernel processes can use the init_heap service to create private nonglobal heaps within their process private region for controlling kernel access to the heap and possibly for performance considerations.

Execution Environment

The init_heap kernel service can be called from the process environment only.