madvise(2) System Calls Manual madvise(2)NAME
madvise - Advise the system of the expected paging behavior of a process
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int madvise ( caddr_t addr, size_t len, int behav );
PARAMETERS
Specifies the address of the region to which the advice refers. Specifies the length in bytes of the region specified by the addr parame-
ter. Specifies the behavior of the region. The following values for the behav parameter are defined in the sys/mman.h header file: No
further special treatment Expect random page references Expect sequential references Will need these pages Do not need these pages
The system will free any whole pages in the specified region. All modifications will be lost and any swapped out pages will be dis-
carded. Subsequent access to the region will result in a zero-fill-on-demand fault as though it is being accessed for the first
time. Reserved swap space is not affected by this call. Ensure that resources are reserved
DESCRIPTION
The madvise() function permits a process to advise the system about its expected future behavior in referencing a mapped file or shared
memory region.
NOTES
Only a few values of the behav parameter values are operational on Tru64 UNIX systems. Non-operational values cause the system to always
return success (zero).
RETURN VALUES
Upon successful completion, the madvise() function returns zero. Otherwise, -1 is returned and errno is set to indicate the error.
ERRORS
If the madvise() function fails, errno may be set to one of the following values: The behav parameter is invalid. The behav parameter
specifies MADV_SPACEAVAIL and resources cannot be reserved.
RELATED INFORMATION
Functions: mmap(2) delim off
madvise(2)
Check Out this Related Man Page
MADVISE(2) BSD System Calls Manual MADVISE(2)NAME
madvise, posix_madvise -- give advice about use of memory
SYNOPSIS
#include <sys/mman.h>
int
madvise(void *addr, size_t len, int advice);
int
posix_madvise(void *addr, size_t len, int advice);
DESCRIPTION
The madvise() system call allows a process that has knowledge of its memory behavior to describe it to the system. The advice passed in may
be used by the system to alter its virtual memory paging strategy. This advice may improve application and system performance. The behavior
specified in advice can only be one of the following values:
MADV_NORMAL Indicates that the application has no advice to give on its behavior in the specified address range. This is the system
default behavior. This is used with madvise() system call.
POSIX_MADV_NORMAL
Same as MADV_NORMAL but used with posix_madvise() system call.
MADV_SEQUENTIAL Indicates that the application expects to access this address range in a sequential manner. This is used with madvise()
system call.
POSIX_MADV_SEQUENTIAL
Same as MADV_SEQUENTIAL but used with posix_madvise() system call.
MADV_RANDOM Indicates that the application expects to access this address range in a random manner. This is used with madvise() system
call.
POSIX_MADV_RANDOM
Same as MADV_RANDOM but used with posix_madvise() system call.
MADV_WILLNEED Indicates that the application expects to access this address range soon. This is used with madvise() system call.
POSIX_MADV_WILLNEED
Same as MADV_WILLNEED but used with posix_madvise() system call.
MADV_DONTNEED Indicates that the application is not expecting to access this address range soon. This is used with madvise() system call.
POSIX_MADV_DONTNEED
Same as MADV_DONTNEED but used with posix_madvise() system call.
MADV_FREE Indicates that the application will not need the information contained in this address range, so the pages may be reused
right away. The address range will remain valid. This is used with madvise() system call.
MADV_ZERO_WIRED_PAGES
Indicates that the application would like the wired pages in this address range to be zeroed out if the address range is
deallocated without first unwiring the pages (i.e. a munmap(2) without a preceding munlock(2) or the application quits).
This is used with madvise() system call.
The posix_madvise() behaves same as madvise() except that it uses values with POSIX_ prefix for the advice system call argument.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.
ERRORS
madvise() fails if one or more of the following are true:
[EINVAL] The value of advice is incorrect.
[EINVAL] The address range includes unallocated regions.
[ENOMEM] The virtual address range specified by the addr and len are outside the range allowed for the address space.
LEGACY SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int
madvise(caddr_t addr, size_t len, int advice);
int
posix_madvise(caddr_t addr, size_t len, int advice);
The include file <sys/types.h> is necessary. The type of addr has changed.
SEE ALSO mincore(2), minherit(2), mprotect(2), msync(2), munmap(2), compat(5)HISTORY
The madvise function first appeared in 4.4BSD. The posix_madvise function is part of IEEE 1003.1-2001 and was first implemented in Mac OS X
10.2.
BSD June 9, 1993 BSD