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)
what i want to do is have an int that can been written into by 2 processes but my code doesn't seem to work.
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include<stdio.h>
#define KEY1 (1492)
int main()
{
int shmid;
volatile int * addr;... (6 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 NETBSD
munlockall
MLOCKALL(2) BSD System Calls Manual MLOCKALL(2)NAME
mlockall, munlockall -- lock (unlock) the address space of a process
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/mman.h>
int
mlockall(int flags);
int
munlockall(void);
DESCRIPTION
The mlockall system call locks into memory the physical pages associated with the address space of a process until the address space is
unlocked, the process exits, or execs another program image.
The following flags affect the behavior of mlockall:
MCL_CURRENT Lock all pages currently mapped into the process's address space.
MCL_FUTURE Lock all pages mapped into the process's address space in the future, at the time the mapping is established. Note that this
may cause future mappings to fail if those mappings cause resource limits to be exceeded.
Since physical memory is a potentially scarce resource, processes are limited in how much they can lock down. A single process can lock the
minimum of a system-wide ``wired pages'' limit and the per-process RLIMIT_MEMLOCK resource limit.
The munlockall call unlocks any locked memory regions in the process address space. Any regions mapped after an munlockall call will not be
locked.
RETURN VALUES
A return value of 0 indicates that the call succeeded and all pages in the range have either been locked or unlocked. A return value of -1
indicates an error occurred and the locked status of all pages in the range remains unchanged. In this case, the global location errno is
set to indicate the error.
ERRORS
mlockall() will fail if:
[EINVAL] The flags argument is zero, or includes unimplemented flags.
[ENOMEM] Locking the indicated range would exceed either the system or per-process limit for locked memory.
[EAGAIN] Some or all of the memory mapped into the process's address space could not be locked when the call was made.
[EPERM] The calling process does not have the appropriate privilege to perform the requested operation.
SEE ALSO mincore(2), mlock(2), mmap(2), munmap(2), setrlimit(2)STANDARDS
The mlockall() and munlockall() functions conform to IEEE Std 1003.1b-1993 (``POSIX.1'').
HISTORY
The mlockall() and munlockall() functions first appeared in NetBSD 1.5.
BUGS
The per-process resource limit is a limit on the amount of virtual memory locked, while the system-wide limit is for the number of locked
physical pages. Hence a process with two distinct locked mappings of the same physical page counts as 2 pages against the per-process limit
and as only a single page in the system limit.
BSD June 12, 1999 BSD