msync.2 (2010 09)

m
msync(2) msync(2)
NAME
msync() - synchronize the memory of a mapped file with physical storage
SYNOPSIS
#include <sys/mman.h>
int msync(
void *addr,
size_t len,
int flags
);
Parameters
addr With len , specifies the region to be synchronized.
len With addr , specifies the region to be synchronized.
flags Specifies one of the following values:
MS_ASYNC
Performs asynchronous writes. The function synchronizes the file contents to match
the current contents of the memory region. If flags is
MS_ASYNC, the function may
return immediately once all write operations have been scheduled.
• All write references to the memory region made prior to the call are visible by
subsequent read operations on the file.
• It is unspecified whether writes to the same portion of the file prior to the call
are visible by read references to the memory region.
• It is unspecified whether unmodified pages in the specified range are also writ-
ten to the underlying hardware.
MS_SYNC
Performs synchronous writes. The function synchronizes the file contents to match
the current contents of the memory region. If flags is MS_SYNC, the function does
not return until all write operations are completed.
• All write references to the memory region made prior to the call are visible by
subsequent read operations on the file.
• It is unspecified whether writes to the same portion of the file prior to the call
are visible by read references to the memory region.
• It is unspecified whether unmodified pages in the specified range are also writ-
ten to the underlying hardware.
MS_INVALIDATE
Invalidates mappings. The function synchronizes the contents of the memory region
to match the current file contents.
• All writes to the mapped portion of the file made prior to the call are visible by
subsequent read references to the mapped memory region.
• It is unspecified whether write references prior to the call, by any process, to
memory regions mapped to the same portion of the file using
MAP_SHARED, are
visible by read references to the region.
DESCRIPTION
The
msync() function writes all modified copies of pages over the range [addr, addr+len] to the under-
lying hardware, or invalidates any copies so that further references to the pages will be obtained by the
system from their permanent storage locations.
addr and len specify the region to be synchronized. If these are not the address and length of a region
created by a previous successful call to
mmap(), msync() returns an error. The behavior of msync()
upon a region created with the MAP_ANONYMOUS or MAP_PRIVATE flags is undefined.
If
msync() causes any write to the file, then the file’s st_ctime and st_mtime fields are marked for
update.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1