[HPADM] SUMMARY: Memory Usage

From: Dave T. (davidlt77@hotmail.com)
Date: Wed Feb 23 2005 - 09:10:02 EST


I received two responses, both of which were informative, and I've posted
them below. Thanks Bill and Martin!

=========================================================
>From Bill Hassell:

That's a fairly good set of commands. There are some minor memory
items that are not visible to normal Unix commands (memory mapped
files, shared libraries, shared text files) and of course the buffer
cache which everyone uses. For a true picture of memory usage, you'll
need Glance.

=========================================================
>From Martin Lodahl:

>Would it be safe to say that to view memory usage by user, execute the
>following:
>
>UNIX95= ps -e -o ruser,pid,vsz=Kbytes

With the proviso that it's a very approximate indicator, yes. The ps(1)
command ignores altogether the kernel and shared objects, but overstates
text memory. Text pages are the program's executable code, which we
certainly hope won't change, so if different processes call for the same
pages, new memory isn't assigned; the new process just points at the
pages already in memory. The ps(1) command makes it look like it's
making new copies every time.

>...and to view shared memory usage, such as for Oracle processes, using the
>following:
>
>ipcs -bmop

There again, the answer is "sort of." It will show shared memory
segments, but it won't differentiate between 32-bit and 64-bit, which
occupy different maps, and it won't show the other shared objects (like
memory-mapped files and I/O addresses) that contend for the same map
space. You can trust what it tells you, but it's pretty far from the
whole story.

=========================================================

----Original Message Follows----
From: "Dave T." <davidlt77@hotmail.com>
To: hpux-admin@dutchworks.nl
Subject: [HPADM] Memory Usage
Date: Mon, 21 Feb 2005 16:23:22 -0500

Would it be safe to say that to view memory usage by user, execute the
following:

UNIX95= ps -e -o ruser,pid,vsz=Kbytes

...and to view shared memory usage, such as for Oracle processes, using the
following:

ipcs -bmop

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