09-30-2010
What Unix do with unused shared memory?
Hello,
When creating shared memory in C, should be remove shared memory with shmctl function when don't need it. If it didn't remove, occupied shared memory stay and remain.
If we create shared memory repeatedly without removing unusable shared memory, /dev/shm will full.
Does Unix or Linux distributions do action to them? For example if a shared memory has 0 shm_nattch and wasn't used in long time, remove them.
10 More Discussions You Might Find Interesting
1. Programming
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)
Discussion started by: joseph_shibu
1 Replies
2. UNIX for Advanced & Expert Users
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)
Discussion started by: cjcamaro
1 Replies
3. Linux
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)
Discussion started by: vijaya2006
0 Replies
4. Programming
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)
Discussion started by: ddx08
6 Replies
5. Programming
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)
Discussion started by: elzalem
9 Replies
6. Programming
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)
Discussion started by: DreamWarrior
12 Replies
7. Programming
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)
Discussion started by: otheus
0 Replies
8. UNIX for Advanced & Expert Users
Hi,
Using ipcs we can see shared memory, etc.. details. How can I add/remove shared memory(command name)?
Thanks,
Naga:cool: (2 Replies)
Discussion started by: Nagapandi
2 Replies
9. AIX
1.How to know wich process is using the shared memory?
2.How to flush (release) the process from the shared memory? (1 Reply)
Discussion started by: pchangba
1 Replies
10. Programming
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 MOJAVE
shm_unlink
SHM_UNLINK(2) BSD System Calls Manual SHM_UNLINK(2)
NAME
shm_unlink -- remove shared memory object
SYNOPSIS
#include <sys/mman.h>
int
shm_unlink(const char *name);
DESCRIPTION
The shm_unlink() function disassociates the shared memory object specified by name from that name. The resources associated with the shared
memory object remain intact until the last file descriptor reference is removed, e.g., by close(2) or munmap(2), at which point the resources
are reclaimed (if no references exist at the time of the call to shm_unlink(), the resources are reclaimed immediately). The name can only
be reused when it is bound to a new shared memory object with a call to shm_open(2) with the O_CREAT flag.
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, and the
named shared memory object will remain unchanged.
ERRORS
The shm_unlink() succeeds unless:
[EACCES] Permission is denied to be remove the object.
[ENAMETOOLONG] name exceeded the name size limit. This is currently PSHMNAMLEN characters (defined in <sys/posix_shm.h>), but this may
change in the future.
[ENOENT] The named object does not exist.
SEE ALSO
close(2), mmap(2), munmap(2), shm_open(2), shmat(2), shmctl(2)
HISTORY
shm_open() is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).
Darwin August 31, 2006 Darwin