03-16-2010
shared memory isn't quite the same thing as /dev/shm. shared mem can be done many ways actually. /dev/shm is essentially a RAM disk.
9 More Discussions You Might Find Interesting
1. 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
2. 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
3. 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
4. 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
5. 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
6. Red Hat
Dear Friends ,
I am confused about shared memory in Linux . plz look @ the below output :
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 126G 61G 59G 52% /
tmpfs 1.7G 0 1.7G 0% /dev/shm
Here , I see that every time... (1 Reply)
Discussion started by: shipon_97
1 Replies
7. Red Hat
unable to remove shared memory using ipcrm -m in linux
$ ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 32768 root 644 80 2
0x00000000 65537 root ... (4 Replies)
Discussion started by: LinuxLearner
4 Replies
8. 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
9. Programming
So I am pretty new to the linux environment, and I am trying to create a shell that uses multiple pipes, and I read online that piping using shared memory space is more efficient than using regular piping. However, I have zero clue how to use shared memory space with pipes. Has anyone done this... (1 Reply)
Discussion started by: Greg_MC
1 Replies
MEM(4) Linux Programmer's Manual MEM(4)
NAME
mem, kmem, port - system memory, kernel memory and system ports
DESCRIPTION
/dev/mem is a character device file that is an image of the main memory of the computer. It may be used, for example, to examine (and even
patch) the system.
Byte addresses in /dev/mem are interpreted as physical memory addresses. References to nonexistent locations cause errors to be returned.
Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.
Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which can be
accessed through this file. For example: on x86, RAM access is not allowed but accessing memory-mapped PCI regions is.
It is typically created by:
mknod -m 660 /dev/mem c 1 1
chown root:kmem /dev/mem
The file /dev/kmem is the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed. Since Linux
2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled.
It is typically created by:
mknod -m 640 /dev/kmem c 1 2
chown root:kmem /dev/kmem
/dev/port is similar to /dev/mem, but the I/O ports are accessed.
It is typically created by:
mknod -m 660 /dev/port c 1 4
chown root:kmem /dev/port
FILES
/dev/mem
/dev/kmem
/dev/port
SEE ALSO
chown(1), mknod(1), ioperm(2)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Linux 2015-01-02 MEM(4)