03-17-2008
HP-UX Trying to Understand Shared Memory Segments
I am fairly new to HP-UX and trying to get a better understanding of the operating system. While poking around a bit I find myself questioning whether I should be concerned about Shared Memory segments with missing CPID and LPID? For example:
ipcs -mp
IPC status from /dev/kmem as of Mon Mar 17 12:36:43 2008
T ID KEY MODE OWNER GROUP CPID LPID
Shared Memory:
m 0 0x411c0846 --rw-rw-rw- root root 720 720
m 1 0x4e0c0002 --rw-rw-rw- root root 720 720
m 2 0x4120127e --rw-rw-rw- root root 720 732
m 48643 0x5e10000b --rw------- root root 2495 2495
The 720 PID is not found any longer. Is this necessarily a problem? The main reason I ask is that we have another server, much busier than this machine and while trying to identify how much shared memory is being used by various processes I have encountered other segments with missing CPID and LPID. Thanks in advance.
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MEM(4) Linux Programmer's Manual MEM(4)
NAME
mem, kmem, port - system memory, kernel memory and system ports
DESCRIPTION
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
FILES
/dev/mem
/dev/kmem
/dev/port
SEE ALSO
chown(1), mknod(1), ioperm(2)
COLOPHON
This page is part of release 3.25 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)