MEM(4) Kernel Interfaces Manual MEM(4)NAME
mem, kmem - main memory
major device number(s):
minor device encoding:
mem: 0; kmem: 1; null: 2
Mem is a special file that is an image of the main memory of the computer. It may be used, for example, to examine (and even to patch) the
Byte addresses in mem are interpreted as physical memory addresses. References to non-existent locations cause errors to be returned.
The file kmem is the same as mem except that kernel virtual memory rather than physical memory is accessed. Only kernel virtual addresses
that are mapped to memory are allowed. Examining and patching device registers is likely to lead to unexpected results when read-only or
write-only bits are present.
On PDP-11s, the I/O page begins at location 0160000 of kmem and the per-process data segment for the current process begins at 0140000 and
is USIZE clicks (64 bytes each) long.
/dev/MAKEDEV script to create special files
/dev/MAKEDEV.local script to localize special files
On PDP-11's, specifying an odd kernel or user address, or an odd transfer count is [generally] slower than using all even parameters.
On machines with ENABLE/34(tm) memory mapping boards the I/O page can be accessed only through kmem.
3rd Berkeley Distribution January 28, 1988 MEM(4)
Check Out this Related Man Page
MEM(4) Linux Programmer's Manual MEM(4)NAME
mem, kmem, port - system memory, kernel memory and system ports
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 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.
It is typically created by:
mknod -m 660 /dev/mem c 1 1
chown root:kmem /dev/mem
The file kmem is the same as mem, except that the kernel virtual memory rather than physical memory is accessed.
It is typically created by:
mknod -m 640 /dev/kmem c 1 2
chown root:kmem /dev/kmem
port is similar to mem, but the I/O ports are accessed.
It is typically created by:
mknod -m 660 /dev/port c 1 4
chown root:mem /dev/port
SEE ALSO chown(1), mknod(1), ioperm(2)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 1992-11-21 MEM(4)
It is just a general question....is there a limit on the memory? I am looking into a process to store image files on the unix server which will be accessed by the application, and I just wonder if there is any limit regarding the physical or virtual memory. I am very new to unix, so thanks for... (1 Reply)
On Alpha True64 UNIX platform, we use "ps aux" command to display the process information, it also displays the %MEM,VSZ, RRS field. The question is that which field really indicates the program's memeory is increasing, thanks (0 Replies)
Hai..I have one question in unix Shell script.Following is the script
System Configuration: lcpu=4 mem=8192MB
kthr memory page faults cpu
----- ----------- ------------------------ ------------ -----------
r b avm fre re pi po fr sr cy ... (1 Reply)
Kindly help me in optimizing the server as it displays a great amount of CPU & MEM being utilised when the mysql process executes.
Below are the stats ---
15:51:57 up 23:22, 5 users, load average:... (1 Reply)
Hello this is a book problem of chapter 8 william stallings's operating systems..can anyone tells me the accurate solution of it??
The Unix kernel will dynamicaly grow a process's stack in virtual memory as needed, but it willnever try to shrink it. Consider the case in which a program calls a C... (7 Replies)
I am working on a script to measure the read performance of a busybox environment. The logical choice is to use a command line like:
(time cp * /dev/null) 2> /tmp/howlong.txt
Ah, the rub is cp or /dev/null will only accept a single file at a time.
The result in the txt file is and... (1 Reply)
I use pstat API to get Process Infomation
I would like to get a process
2.how many physical memory and virtual memory and total memory used(KB) and usage(%)
3.a process excution file create time
4.a process excution file access time
I do't know which attribute it i need
... (3 Replies)
I ned to monitor the memory for the red-hat machine,when its reaches a threshold value like 2GB then a mail should be sent as soon as it finds the the value is met
can you suggest me which is the best way to do this? (2 Replies)
I'm looking into doing a few performance tweaks by adjusting my max memory on a few lpars.
I would to create a time stamp script so i could review it for a week and determine how much space i can lower my max memory to so i could reclaim and allocate that memory to where it is needed the... (2 Replies)
We know for every process, it has 4G virtual memory on a 32bit machine.
since virtual memory is not physical memory, why don't operating system allocate all it's virtual memory to it, but set a "program break" to limit it's heap space?
Even if the operating system allocate all the 4G virtual... (6 Replies)
Hi, Paging on one of my boxes has been bloating up while physical memory is still available.
Avg Phys Mem - 85% (of 96GB)
Avg Paging: - 55% (of 24GB)
Last week, the box ran out of paging while physical memory still reported 84% usage. Any idea what I'm missing out here?
#... (2 Replies)