Dear Reader,
Is is necessary to attach / dettach the shared memory segments for write operations , if more than one program is accessing same shared memory segments..
I have used semaphore mutex and still I'm getting segmentation fault when I write to the segment when other program is already... (1 Reply)
I am running HP-UX B.11.11.
I'm increasing a parameter for a database engine so that it uses more memory to buffer the disk drive (to speed up performance). I have over 5GB of memory not being used.
But when I try to start the DB with the increased buffer parameter I get told.
"Not... (1 Reply)
Hi all :confused: ,
I am new to unix.I have been asked to implement shared memory in user's mode.What does this mean?What is the difference it makes in kernel mode and in users mode?What are the advantages of this impemenation(user's mode)?
And also i would like to know why exactly shared... (0 Replies)
hi all
I have been asked to implement shared memory in user mode?But :rolleyes: im not understanding how to do this.And what does it mean in user mode?Is it that we need to simulate what kernal does...like attaching ,detaching memory..etc...?
And would also like to know why shared memory is... (3 Replies)
hi,
this is the problem: i want to swap a linked list between 4 processes (unrelated), is there any way i can do that just by sending a pointer to a structure?
//example
typedef struct node
{
int x;
char c;
struct node *next;
} node;
or i should send the items ( x,c ) by... (9 Replies)
I need to create a shared library to access an in memory DB. The DB is not huge, but big enough to make it cumbersome to carry around in every single process using the shared library. Luckily, it is pretty static information, so I don't need to worry much about synchronizing the data between... (12 Replies)
I am writing a shared library in Linux (but compatible with other UNIXes) and I want to allow multiple instances to share a piece of memory -- 1 byte is enough. What's the "best" way to do this? I want to optimize for speed and portability.
Obviously, I'll have to worry about mutual exclusion. (0 Replies)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
Discussion started by: iamjag
5 Replies
LEARN ABOUT ULTRIX
munmap
munmap(2) System Calls Manual munmap(2)Name
munmap - unmaps memory of a character device
Syntax
#include <sys/types.h>
#include <sys/mman.h>
caddr_t munmap(addr, len)
caddr_t addr;
size_t len;
Arguments
addr Specifies the address space of the calling process at which the unmapping begins.
len Specifies the number of bytes to unmap.
Description
The system call unmaps a specified number of bytes (len) starting at a specified address (addr) from the address space of the calling
process. You mapped this device in a previous call to Subsequent access to the unmapped region results in a signal. You cannot unmap
data, stack, and text segments using
The system call rounds len to the nearest multiple of page size as returned by
The range [addr, addr + len] may contain more than one mapped region created by In this case, unmaps all of the mapped regions.
Restrictions
All of the mapped regions must be wholly contained in the range [addr, addr + len]. That is, addr must be the beginning of some mapped
region and addr + len must be the end of some (possibly different) mapped region.
Return Value
If successful, returns 0. Otherwise, it returns -1 and sets the errno argument to one of the errors listed in the Diagnostics section.
Diagnostics
The call to fails if one or more of the following is true:
[EINVAL] The address you specified in addr is not a multiple of the page size as returned by
[EINVAL] The addresses in the range [addr, addr + len] are not valid in the process address space.
[EINVAL] All of the segments being unmapped are not entirely contained in the range [addr, addr + len].
See Alsogetpagesize(2), getsysinfo(2), mmap(2)munmap(2)