Mac OS X / Darwin man pages : madvise (2)
madvise (2)
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madvise - give advice about use of memory
#include <sys/types.h>
#include <sys/mman.h>
int
madvise(caddr_t addr, size_t len, int behav);
int
posix_madvise(caddr_t addr, size_t len, int behav);
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 behav can only be one of the following values:
- MADV_NORMAL
- Indicates that the application has no advice to give on
its behavior in the specifed 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.
The posix_madvise() behaves same as madvise() except that it uses values
with POSIX_ prefix for the behav system call argument.
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
madvise() fails if one or more of the following are true:
- [EINVAL]
- The value of behav is incorrect.
- [ENOMEM]
- The virtual address range specified by the addr and
len are outside the range allowed for the address
space.
- [EINVAL]
- The address range includes unallocated regions.
mincore(2)
, minherit(2)
, mprotect(2)
, msync(2)
, munmap(2)
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.
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