Mailing List Archive

On Sun, Jul 06, 2003 at 10:42:53AM +0200, Magdy Albatooty (EG/EEL) wrote:
> Hi,
>
> The command "show system virtual-memory" displays the following:
>
> Memory Totals: In Use Free Requests
> 5497K 80K 15304448
>
> Why is free space too low? Is this normal?

This shows the allocation of memory within the kernel, and is completely
normal. You want the "free" space value here to be low, as this means you
are not wasting memory unnecessarily.

> Also, command "show system storage" shows several 100% capacity. Is this
> normal?

Anything mounted off a /dev/vn#, devfs, or procfs is by definition going
to be at 100% capacity.

--
Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

> From: "Magdy Albatooty (EG/EEL)" <magdy.albatooty@ericsson.com>
> Date: Sun, 6 Jul 2003 10:42:53 +0200
> Sender: juniper-nsp-bounces@puck.nether.net
>
> Hi,
>
> The command "show system virtual-memory" displays the following:
>
> Memory Totals: In Use Free Requests
> 5497K 80K 15304448
>
> Why is free space too low? Is this normal?
>
> Also, command "show system storage" shows several 100% capacity. Is this normal?

Under the hood, JunOS is FreeBSD and (like several other flavors of
UNIX), it creates "special" file systems to allow access to kernel
stuff like devices and the like. These (/dev and /proc) are always at
100%, by definition.

JunOS also uses FreeBSD "vn" (vnode) devices to mount several odds and
ends. These are actually complete file systems written to a single
disk file. While they may be created as read-write file systems and
have free space, in the case of JunOS they are read-only and the file
systems are created exactly big enough to hold the desired information,
so they are always at 100%.

"ad" devices are "real" disk partitions. "mfs" is also "real", but it
exists in memory (Memory File System) rather than on a physical
drive.

As to the memory situation, what you are seeing is not unusual for
FreeBSD. It typically keeps a lot of memory that is "free" in the used
category so that it can be paged back in if needed. If memory is
needed, it is available, but if it needs to be paged in, it's already
there.

I will admit that 80K does look a bit tight, but it is probably not.
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net Phone: +1 510 486-8634

Hi,

Regarding the tight memory space, will the system generate an early alert/alarm if there is actually low memory space available?

BR,
Magdy



-----Original Message-----
From: Kevin Oberman [mailto:oberman@es.net]
Sent: Mon, July 07, 2003 8:39 PM
To: Magdy Albatooty (EG/EEL)
Cc: juniper-nsp@puck.nether.net
Subject: Re: [j-nsp] Memory questions.


> From: "Magdy Albatooty (EG/EEL)" <magdy.albatooty@ericsson.com>
> Date: Sun, 6 Jul 2003 10:42:53 +0200
> Sender: juniper-nsp-bounces@puck.nether.net
>
> Hi,
>
> The command "show system virtual-memory" displays the following:
>
> Memory Totals: In Use Free Requests
> 5497K 80K 15304448
>
> Why is free space too low? Is this normal?
>
> Also, command "show system storage" shows several 100% capacity. Is this normal?

Under the hood, JunOS is FreeBSD and (like several other flavors of
UNIX), it creates "special" file systems to allow access to kernel
stuff like devices and the like. These (/dev and /proc) are always at
100%, by definition.

JunOS also uses FreeBSD "vn" (vnode) devices to mount several odds and
ends. These are actually complete file systems written to a single
disk file. While they may be created as read-write file systems and
have free space, in the case of JunOS they are read-only and the file
systems are created exactly big enough to hold the desired information,
so they are always at 100%.

"ad" devices are "real" disk partitions. "mfs" is also "real", but it
exists in memory (Memory File System) rather than on a physical
drive.

As to the memory situation, what you are seeing is not unusual for
FreeBSD. It typically keeps a lot of memory that is "free" in the used
category so that it can be paged back in if needed. If memory is
needed, it is available, but if it needs to be paged in, it's already
there.

I will admit that 80K does look a bit tight, but it is probably not.
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net Phone: +1 510 486-8634